*1995-2005 Most Active 11-Year Period On Record*
Hurricane activity has been on the rise since the 1995 season. From 1995 through 2005, the Atlantic Basin experienced its most active 11-season hurricane period on record.
For the Atlantic Hurricane Season:
1933 had the most tropical systems -- 21. But 2005 broke the record: 27
1969 held the record for most hurricanes -- 11. But 2005 broke the record: 14
1950 holds the record for most intense ("major") storms -- 8 (season 2005 had 7).
Only July 1916 and July 2005 (Dennis and Emily) had two major hurricanes so early.
According to Census figures, more than 48 million people live within 50 miles of the Gulf and Atlantic coasts.
The nation's coastlines had major population increases during the decades with low storm activity before 1995.
**UPDATE** Recent analyses and studies suggest global warming may be a factor in making tropical storms stronger. The number of Category 4 and 5 hurricanes increased worldwide between 1975-1989 and 1990-2004. Worldwide between 1975-89, there were 171 Category 4/5 systems, with 16 of those in the North Atlantic. Between 1990-2004, there were 269 Cat 4/5 systems worldwide, with 25 of those in the North Atlantic.
To estimate the total rainfall in inches from a hurricane, divide 100 by the forward speed of the storm in miles per hour: (100 / forward speed = estimated inches of rain)
|CAT||Wind Speed||Storm Surge|
|Major Hurricanes in November|
|*Had maximum sustained winds of 150 mph.|
DR. GRAY'S TEAM EXPECTS BUSY 2013 ATLANTIC SEASON
... 9 Hurricanes, 18 Named Storms
The first forecast for the six-month 2013 hurricane season doesn't look much different than what happened in the 2012 season.
Professor William Gray and research scientist Philip Kloztbach from Colorado State University's Department of Atmospheric Science say the Atlantic basin can expect 18 named storms, 95 named storm days, nine hurricanes, 40 hurricane days, four major hurricanes (sustained winds of 111 mph or higher) and nine major hurricane days.
In 2012 there were 19 named storms, nine of which attained hurricane strength at some point.
But it was the seventh consecutive year a hurricane didn't make landfall in Florida, which National Hurricane Center spokesman Dennis Feltgen said is a record dating back to 1851.
The main reason for this year's forecast, the Colorado State team said, is largely due to an expected lack of an El Nino. A weak El Nino weather pattern is when warm water temperatures in the Pacific tend to push damp weather east. A strong El Nino tends to minimize hurricanes during the storm season.
The Colorado State researchers say there is a 72 percent chance that a major hurricane (Category 3 or higher) could make landfall along the "entire U.S. coastline." That goes down to 48 percent for the "U.S. East Coast including peninsula Florida."
On the Gulf of Mexico side, they forecast a 47 percent chance of landfall from Florida's Panhandle to Brownsville, Texas.
In 2012, the primary storm to affect the Keys was Hurricane Isaac, which blew through as a tropical storm Aug. 26 and 27. Sustained winds in the Keys were 45 mph to 50 mph. Damage was minor but a lot of rain fell.
Hurricane Sandy, which caused billions of dollars in damage and killed more than 100 people in the Northeast in late October 2012, only mildly affected the Keys, as just strong winds from Sandy's outer bands were felt.
Sandy has been retired from the list of tropical storm names because of the catastrophic damage its massive size and strength caused along the East Coast in 2012.
National Oceanic and Atmospheric Administration officials say the name Sara will take its place. Sandy was retired from the official list of Atlantic Basin tropical storm names by the World Meteorological Organization's hurricane committee.
Storm names are recycled every six years unless they're retired because of extreme damage or a considerable number of casualties.
Sandy is the 77th storm name taken off the list since 1954. The National Hurricane Center has attributed 72 deaths from Maryland to New Hampshire directly to Sandy, though some estimates were higher. It wiped out entire neighborhoods and was one of the country's costliest natural disasters.
NOAA EXPECTS NORMAL 2012 ATLANTIC SEASON
... El Niño a Mitigating Factor; Dr Gray's Forecast Included Below
Officials with the National Oceanic and Atmospheric Administration (NOAA), the federal agency that studies and tracks severe weather, made the announcement at a press conference in Miami. Hurricane season runs from June 1 to Nov. 30, though storms can, and have, formed outside of those dates when conditions were favorable.
The outlook indicates a near-normal season is likely, with a total of nine to 15 named storms for the Atlantic in 2012. (Named storms include tropical storms and hurricanes.) Of those storms, between four and eight are likely to become hurricanes — organized, rotating storms with sustained winds of 74 mph (119 kph) or faster. Between one and three are likely to become major hurricanes, defined as Category 3 storms or above — hurricanes with winds of at least 111 mph (179 mph).
The potential mitigating factor in the mix is El Niño, officials said, because of the effects it has on winds in the upper atmosphere that can impede the growth of a burgeoning storm.
"El Niño tends to increase the wind shear, and that tends to suppress or kill off hurricanes," said Gerry Bell, lead hurricane season forecaster at NOAA's Climate Prediction Center. "So if El Niño forms, that would be a limiting factor to the season's strength."
El Niño is a cyclical warming of Pacific Ocean waters that has wide-reaching climate effects. It is the flipside of La Niña, a cyclical cooling of those waters; a powerful and long-lasting La Niñaonly recently came to an end, with neutral conditions now in place.
This year's outlook for a maximum of 15 named storms and three major hurricanes "is a little less than some of these active seasons, but that's still a lot of activity," Bell said. "It doesn't mean anybody is off the hook at all."
However, the forecast does mark a lull in activity compared with the 2011 hurricane season, which was one of the most active on record for the Atlantic basin.
Seven hurricanes and 13 tropical storms barreled across the region in 2011. The first named storm of the season, Tropical Storm Arlene, arrived on the scene on June 28; the final storm of the season, Tropical Storm Sean, fizzled out on Nov. 11.
Although the majority of the 2011 season's storms spared the United States, Hurricane Irene caused widespread destruction, and was one of a dozen billion-dollar weather disasters to hit the United States last year.
The first named storm of the 2012 season, Tropical Storm Alberto, spun up on May 19, ahead of the official start to the season, and was gone by May 22.
Tim Manning, FEMA deputy administrator for protection and national preparedness, urged those who live in hurricane-prone areas to prepare now, adding that families should draw up a plan, and makes sure to have three days of food, water and emergency supplies on hand.
"It takes just one storm to come ashore to create a disaster," he said.
Colorado State University forecasters predict up to 15 named storms will form during the 2012 hurricane season. University forecasters have released the annual report for the last three decades.
According to the report, there is a 45 percent chance for an above-average hurricane season in 2012. Typically, that means 12 to 15 named storms will form between June 1 to November 30.
Forecasters expect seven to nine of those named storms to become hurricanes, with three to four of them categorized as major hurricanes. Any storm category 3 and above is considered a major hurricane.
The major factor that helps university forecasters create their annual report is Atlantic Thermohaline Circulation (THC).
"When THC is stronger than normal, the tropical Atlantic [is] typically more conducive for hurricane formation and intensification," forecasters said.
MASON-DIXON POLL ON HURRICANE PREPAREDNESS
... Disaster Officials Launch Initiative to Bring Life-Saving Information to Citizens in Hurricane-Vulnerable States
The most alarming key findings represent "the first early-warnings" that concern emergency management officials. Of those surveyed:
* 53% don't feel vulnerable to a hurricane or related tornado or flooding,
* 52% have no family disaster plan,
* 61% have no hurricane survival kit,
* 88% have taken no steps to make their homes stronger,
* And 16% said they might not or would not evacuate even if ordered to do so, leaving thousands of residents at grave risk in the path of any given storm.
Despite the historic and devastating hurricane seasons of 2004 and 2005, this Mason-Dixon poll reveals a dangerously high percentage of residents in hurricane-vulnerable states still aren’t prepared, don’t take the threat of hurricanes seriously and have big gaps in what they know about hurricanes – even among those who live within 30 miles of the coast.
“Nearly two years after Hurricane Katrina shocked and horrified the nation, far too many residents are still unprepared for storms,” said Bill Proenza, director of the National Hurricane Center. “The 2007 below-normal hurricane season may have resulted in coastal residents being lulled into a false sense of complacency. The 2008 hurricane season promises to be an active one, so it is imperative residents get ready before a storm catches them unprepared.”
The Mason-Dixon poll was commissioned by the organization American Initiatives
KAREN UPGRADED AS 2007 ATLANTIC SEASON ENDED
... Atlantic Season ends with near-average activity
U.S. weather experts posthumously upgraded Tropical Storm Karen to a hurricane as the 2007 Atlantic storm season ended, making the year a near-average one for hurricane activity.
The U.S. National Hurricane Center, in a post-season analysis of Karen, said the storm briefly reached hurricane intensity on September 26, with winds of 65 knots, equal to 74.8 mph (120 kph) or just over the threshold at which tropical storms become hurricanes.
The upgrade of Karen took the 2007 season's hurricane toll to six. The 14 named storms that formed exceeded the long-term average of around 10 for a six-month Atlantic hurricane season.
But most of the storms were short-lived, meaning the so-called accumulated cyclone energy index, which measures the collective strength and duration of storms and hurricanes, reached only about 82 percent of the 1951-2000 median, "the lowest observed since 2002," the hurricane center said.
Only one hurricane -- Humberto -- hit the United States this year. It was relatively weak and a far cry from the destruction wrought by hurricanes Katrina, Rita and Wilma in the record-setting season of 2005.
Two of the current season's hurricanes did reach maximum Category 5 strength on the five-step Saffir-Simpson scale of intensity.
Hurricane Dean in August slammed into Mexico's Yucatan Peninsula and killed around 27 people throughout the Caribbean, while Hurricane Felix in September plowed into Nicaragua, killing more than 100.
The season's deadliest storm was also its last, Hurricane Noel, which doused the Dominican Republic and Haiti and triggered floods and mudslides that killed more than 150 people in the neighboring countries.
CRUCIAL WEATHER SATELLITE COULD FAIL ANYTIME
...QuikScat's age could impact hurricane forecasts if it falters
An aging weather satellite crucial to accurate predictions on the intensity and path of hurricanes could fail at any moment, and plans to launch a replacement have been pushed back seven years to 2016. In a letter obtained by the Associated Press, the National Oceanic and Atmospheric Administration's chief said the failure of the QuikScat satellite could bring more uncertainty to forecasts and widen the areas placed under hurricane watches and warnings.
If the satellite faltered, experts estimate the accuracy of two-day forecasts would suffer by 10 percent and three-day forecasts by 16 percent, which could translate into miles of coastline and the difference between a city being evacuated or not. In the letter to a Florida congressman, NOAA chief Conrad Lautenbacher blamed the delays on technical and budget problems. Scientists said if QuikScat failed, they may have to rely on less accurate satellites.
QuikScat, launched in 1999 and designed to last two to three years, provides key data on wind speed and direction over the ocean. Weather aircraft and buoys also can obtain similar measurements near a storm, but they do not provide a constant flow of data as QuikScat does.
In 2006, the satellite suffered a major setback - the failure of a transmitter used to send data to Earth about every 90 minutes. The satellite is limping along on a backup transmitter and has other problems. The backup transmitter could last years, but there are no guarantees and no warnings when it is about to fail, said an offical who works with the satellite at NASA's Jet Propulsion Laboratory.
SOME FORECASTERS CALL FOR NEW HURRICANE CLASSIFICATION
... Based also on the Storm's Size and Reach
Forecasters are calling for a new system to predict a hurricane's damage potential, one that could have saved lives taken by Hurricane Katrina and that would be based on the storm's size and reach, not just its wind speed and push.
Currently, hurricanes are classified with the Saffir-Simpson scale, which gives them a 1 to 5 rating based on the strength of a storm's winds, the pressure at the center of the storm (also called it's eye) and the amount of ocean water the storm's winds push on shore, called storm surge. (A Category 1 hurricane's winds blow at 74 to 95 mph and Category 5 storms rage faster than 150 mph.)
But these factors don't always give the full picture of how violent and destructive a storm will be, researchers say, pointing out that the area of a storm and how far out from its center the strong winds reach also influence the amount of damage it can do.
"The Saffir-Simpson scale has been a very valuable tool in warning people about hurricanes," said an engineer of the Institute for Business & Home Safety, a non-profit agency that does research aimed at reducing the social and economic effects of natural disasters. "But we have known for some time that the level of surge and surge-related damage is not well correlated with the maximum wind speeds at landfall." The quoted engineer is also a former deputy director of the Federal Emergency Management Agency.
A prime example of this problem, the researchers say, is Hurricane Katrina: Katrina was a Category 5 just 24 hours before landfall, but downshifted to a 3 by the time it touched Gulf shores. In comparison, Hurricane Camille, which devastated the same area in 1969, killing 259 people and causing nearly $1.5 billion dollars in damage, had much stronger winds than Katrina. But Katrina's wind field extended over a much wider area and caused much more significant coastal flooding, making it the costliest and deadliest hurricane in United States history, taking nearly 2000 lives and causing $81 billion in damage.
Many Mississippi residents may have relied on their memory of Camille in their decision not to evacuate, the researchers argue, and call for a new Hurricane Destructive Potential classification tat could better alert coastal resident's to a storm's potential for damage.
"By incorporating both size and intensity, I see this system as a better way to allow people to assess the true potential impact of an approaching storm," said a meteorologist with the Atlantic Oceanographic and Meteorological Laboratory in Miami. "If people knew that Katrina had a much higher damage potential than Camille, then Mississippi residents who chose to stay might have evacuated."
DOES 2007 ATLANTIC SEASON RE-ENERGIZE?
... Maybe 2006 was just a brief respite?
The relative calm of the 2006 Atlantic hurricane season will be just a short respite before above-average storm activity resumes next year, a noted U.S. hurricane forecasting team says.
The prediction by forecasting pioneer Dr. William Gray's team at Colorado State University was the second warning in two days from reputable forecasters that the 2007 hurricane season was likely to be busier-than-average, and that powerful storms like Hurricane Katrina could again threaten the United States.
The CSU forecasters led by Gray and Philip Klotzbach said the 2007 season was expected to bring 14 tropical storms, of which 7 will strengthen into hurricanes with winds of at least 74 miles per hour (119 km per hour). Three of those were expected to become more destructive "intense" hurricanes of Category 3 or higher on the five-step Saffir-Simpson scale.
The long-term average for the Atlantic is for 10 storms to form during the six-month season, which begins on June 1, and for six of those storms to reach hurricane strength.
Like other forecasters, the CSU team mistakenly predicted a busy 2006 hurricane season, on the heels of a record 28 storms and 15 hurricanes in 2005 and an only slightly less ferocious season in 2004. Instead, the season just ended spawned a below-average nine storms, of which five became hurricanes.
None of the hurricanes hit the United States, bringing relief to residents of the U.S. Gulf Coast, where Katrina killed 1,500 people, swamped the city of New Orleans and caused $80 billion in damage. Relief has also been palpable in Florida, which was struck by a series of hurricanes in both 2004 and 2005.
The hurricane experts say the unexpected formation of an El Nino weather phenomenon mid-summer caught them by surprise. An unusual warming of eastern Pacific waters, el Nino weather events tend to suppress Atlantic storm activity.
The 2007 Atlantic hurricane season is expected to be more active than the average 1950-2000 season. However, this is an early prediction. One of the important questions for the upcoming season is whether El Nino conditions will continue through 2007.
This active cycle is expected to continue for another decade or two at which time we should enter a quieter Atlantic major hurricane period like we experienced during the quarter-century periods of 1970-1994 and 1901-1925.
[ originally posted 11/30/05 ]
THE 2005 ATLANTIC HURRICANE SEASON
... A New Benchmark to Measure By
The 2005 Atlantic Hurricane Season obliterated many long-standing records:
-- In 154 years of record-keeping, 2005 had the most named storms (27), the most hurricanes (14, including Epsilon on 12/2/05), the highest number of major hurricanes hitting the U.S. (4), and the most top-scale Category 5 hurricanes (raised from 3 to 4, as Emily was upgraded to a Cat 5 by NOAA on 3/10/06. Emily is the only Cat 5 hurricane ever to form before August, as it became a Cat 5 on 7/16/05).
-- Tropical Storm Zeta (the 27th named system) formed on December 30, 2005.
-- Katrina was the deadliest U.S. hurricane since 1928 (more than 1,300 dead) and replaced 1992's Andrew as the most expensive one on record ($34.4 billion in insured losses).
-- Total insured losses from hurricanes this year were put at $47.2 billion, above the previous record of $22.9 billion set last year when four hurricanes also hit the U.S., according to risk-analysis firm ISO.
-- Wilma was briefly the most intense Atlantic hurricane on record in terms of minimum central pressure (882 millibars). It also was the fastest-strengthening storm on record -- its top sustained winds increased 105 mph in 24 hours in the Caribbean.
-- Forecasters exhausted their list of 21 proper names (Arlene, Bret, Cindy and so on) and had to use the Greek alphabet to name storms for the first time. The 2005 season was the earliest for having 7 named tropical systems/storms (TS) (by end of July). In the years that had at least eight storms -- only about ½ of all seasons since 1851 -- the mean date of formation for the 8th storm is September 29th. Harvey was the earliest-forming 8th TS (8/3/05), Irene the earliest 9th TS (8/7/05), Jose the earliest 10th-named TS (8/22/05) and Katrina the earliest 11th-named TS (8/24/05). This record-setting pace continued all season, with the 19th-named system, Tammy (10/5/05), beating the 1933 record by 20 days. Greek letters were later used in the season, up to Epsilon (11/29/05 named and became a hurricane on 12/2/05).
-- The worst damage, of course, was inflicted by Katrina. Miles of coastal Mississippi towns such as Waveland and Gulfport were smashed. Eighty percent of New Orleans was under water after its levees broke. The world saw families stranded on roofs, and hungry and thirsty refugees stuck in the Superdome and Convention Center. Bodies lay on streets for days or floated in the fetid floodwaters. By December, 2005 hundreds of thousands of people had yet to return to their homes -- or had no homes to return to.
-- By the end of the 2005 Atlantic season, Congress had so far approved $62 billion in mostly short-term relief aid, and estimates put the cost of rebuilding at up to $200 billion.
THE GATHERING WINDS
... A Rise in Deadly Storms Since '95 Has Researchers Worried About the Future
First, there was Opal (1995). Then Fran (1996), Floyd (1999) and Allison (2001). But the string of deadly billion-dollar storms blowing in from the Atlantic was far from over.
In 2004, the quartet of Charley, Frances, Ivan and Jeanne ravaged Florida in rapid succession and set records for damage. Then, somehow, it got worse. With Katrina, the inundation of New Orleans and an Atlantic storm season so active it stretched forecasters beyond the normal alphabetical list of names into the Greek of Alpha, Beta, Gamma, and Delta, 2005 racked up more storm deaths and destruction than the previous 10 years -- combined.
So while the end of 2005's hurricane season allowedresidents along the Southeast coast to heave a sigh of relief, it also points to a growing worry: What is going on with the weather?
With the surge in hurricanes since 1995, droves of people moving to affected coastal areas and the federal government spending billions in storm relief annually, the question has rarely seemed so urgent.
"People talk about what is 'normal' for hurricanes, but there's a new definition of 'normal' now," said Roger Pielke Jr., an environmental studies professor at the University of Colorado. "This is out of people's range of experience. But there will be far more activity and far more destruction."
Many storm researchers now agree that a decade or more of similarly rough seasons -- similar to the heightened storm activity that began in 1995 -- lies ahead.
But at the same time that the trio of Katrina, Rita and Wilma were battering Southeastern coasts, a controversy was brewing over the reasons for the rise in hurricane havoc. At issue: Is it merely a natural fluctuation or, more ominously, a product of global warming?
Until recently, a rough consensus in the small world of tropical cyclone specialists had held that there was no evidence of unnatural hurricane trends over the 20th century. Hurricane activity over the Atlantic has fluctuated naturally over decades going back as far as 1900, and it was unlikely that global warming could be having a significant impact, many researchers said.
But a pair of scientific papers published this year detected an unexpected spike in storm intensity over the past several decades, suggesting that global warming might already be having an effect. The research set off a passionate and sometimes personal debate in the small community of storm scientists.
"In the sense of the history of scientific ideas, we're either in the middle of a paradigm shift or a false paradigm shift," said Hugh Willoughby, the former director of hurricane research at the National Oceanic and Atmospheric Administration. "The situation would be deliciously ambiguous if there were not thousands of lives and billions of dollars on the table."
Besides adding weight to the argument that global warming could be having catastrophic effects, the findings spell more trouble for U.S. coastal areas vulnerable to fierce storms, where the population is rising fast. The risks are being borne by all U.S. taxpayers. Already, the federal government has been asked repeatedly for hurricane relief money.
"We have to decide as a society whether that's a problem," Pielke said. "Obviously, the benefits of living near the coast outweigh the costs because people are doing it. The question is: In the face of inevitable property damage and loss of life, how well do we prepare?
"Either way," he noted, "we are going to see many more years of intense hurricanes. Scientists on both sides agree on that."
The difference between the two scientific views is whether hurricane activity will simply fluctuate over time, as it apparently has done in the past, or whether global warming will inexorably ramp up the damage.
The opening skirmish in the debate began when Kerry Emanuel, a well-known researcher at the Massachusetts Institute of Technology, changed his mind. In July, he withdrew from a paper reflecting the consensus view that there was little evidence of a significant connection in the historical record. In an e-mail, he wrote to a co-author that "the problem for me is that I cannot sign on to a paper which makes statements I no longer believe are true."
"I see a large global warming signal in hurricanes," he wrote.
The next month, he published a paper in Nature considering 50 years of storm data and stating that indeed, hurricanes in the Atlantic and North Pacific were becoming more powerful. By a special measure of hurricane power he had defined for other research, they had roughly doubled in power over 30 years. Significantly, the increase tracked with the rise in sea surface temperatures.
There was more to come. In September, a group of scientists led by Peter Webster at Georgia Tech found that, worldwide, the number of the strongest hurricanes -- categories 4 and 5 -- has nearly doubled over the past 35 years. The authors aligned the finding with global warming and a rise in sea surface temperatures.
"Our work is consistent with the concept that there is a relationship between increasing sea surface temperature and hurricane intensity," Webster said at the time.
But he also noted that the findings did not perfectly fit with global warming. "It's difficult to explain," he said, why, when sea surface temperatures were rising the most in the past decade, the number of hurricanes and their longevity decreased. Even with such cautions, however, reaction to the papers was immediate and powerful.
Some environmental groups touted the studies as a reason to immediately restrict carbon emissions in an effort to slow global warming. At the same time, other researchers launched tirades against the findings.
William Gray of Colorado State University, well known for his annual hurricane season forecasts, was at the forefront of the criticisms.
"If true, this is a very important finding that has great relevance as regards the globe's future climate and future hurricane destruction," he wrote in rebuttal to Emanuel's paper. "But the author's 'apparent' blockbuster results and his interpretation of his calculations are not realistic."
There are at least two fundamental problems with the studies, according to Gray and others. The first is that Atlantic hurricane activity has long been known to undergo fluctuations over long periods. The flip-flops between active and inactive hurricane periods in the Atlantic are attributed to long-term trends in currents and salinity.
The 1950s and 1960s saw lots of hurricane activity, for example, whereas the '70s, '80s and early '90s did not. The uptick in hurricanes that began in 1995 had long been anticipated, though researchers hadn't been sure when exactly the change would come. Critics said the rise in Atlantic hurricanes that the papers detected was probably the cause of this natural "oscillation," not global warming.
The second flaw in the papers, according to critics, is that both papers are based on hurricane records over decades, and those vary in quality, largely because the means of measuring hurricane intensity have changed over time.
In the northwest Pacific, for example, which sees a large share of hurricane-force storms, records of storm intensity have at times been based on flight observations and sometimes on satellite images.
"In a nutshell, the data sets they're using aren't reliable enough to answer those important questions," said NOAA hurricane researcher Christopher W. Landsea. "The data sets don't take into account the different ships, the different planes, the different satellite imagery. The data is affected by the different ways of measuring."
For all the skepticism from some quarters, the arguments have been persuasive elsewhere. Willoughby said he has been leaning toward the global warming explanation and that the two new papers helped.
Still, he said, it is too early to tell.
"Right now, I don't think there is a consensus answer," he said. "There are just a lot of smart people doing good work on a very important question."
STUDY: HURRICANES ARE GROWING STRONGER
... Findings sure to add fuel to global warming debate
When Hurricane Katrina roared out of the Gulf of Mexico with 145 mph winds, it was the latest in what scientists today cited as a growing number of fearsome Category 4 and 5 storms that form each year in the world's tropical oceans. In a study published in the journal Science, researchers reported satellite data showing that the number of the most violent tropical storms increased almost 80 percent in 2004 over the number in 1975.
The paper - the first global assessment of hurricane activity - draws a link between the rising number of big storms and increases in tropical sea surface temperatures around the world. Although the study itself stops short of blaming global warming for the trend, its authors were less reticent to draw a connection at a news conference this week.
"With some confidence we can say these two things [more violent storms and rising ocean temperatures] are connected, and there's probably a substantial contribution from greenhouse warming and not just natural variability," said study co-author Judith Curry of the Georgia Institute of Technology.
The findings are certain to add fuel to the debate over global warming and its influence on weather events.
The 2005 Atlantic hurricane season will go down as one of the most active in years. Dennis and Emily reached Category 4 on the Saffir-Simpson scale (131 mph), while Katrina hit Category 5, the highest, at 155 mph. But there are a variety of opinions as to why - and whether it's part of a larger trend.
During the 2005 spring, scientists at the National Hurricane Center independently predicted the increase in violent storms - but without invoking global warming. They cited a recurring cycle of sea-surface temperatures, atmospheric pressure and wind conditions peculiar to the tropical Atlantic. The increased activity began in 1995 and could last for decades.
Today's study in Science, a publication of the American Association for the Advancement of Science, is much broader. It addresses a 35-year global rise in tropical ocean temperatures that the authors argue drives up the intensity of hurricanes in all ocean basins.
Curry, along with her Georgia Tech colleagues Peter J. Webster and Hai-Ru Chang, and Greg Holland of the National Center for Atmospheric Research, focused on the period from the 1970s through 2004. That so-called "satellite era" of weather records offered the best and most globally consistent set of observations.
Curiously, they found no increase in the total number and duration of tropical storms and hurricanes. In fact, in every ocean basin except the North Atlantic, their frequency and duration actually fell after 1995 - a period in which sea surface temperatures were rising the most.
"No global trend has yet emerged in the number of tropical storms and hurricanes," the paper concluded.
"We don't have a simple theory to explain that," Curry said.
But the data did reveal a sharp increase everywhere in the fiercest storms. Category 4 and 5 hurricanes were up about 80 percent between 1975 and 2004. Those are the most powerful storms on the Saffir-Simpson hurricane scale - with winds over 131 mph.
During the same period, sea surface temperatures were rising in all tropical ocean basins, by about a half-degree Celsius. on average. Because rising sea-surface temperatures are a global phenomenon, probably influenced by greenhouse warming, the scientists said, they offer the best explanation for global increases in the number of intense hurricanes. Global warming theorists have predicted for decades that rising air and sea temperatures - driven by fossil fuel use and greenhouse gas emissions-would increase the frequency and intensity of storms around the world.
Brenda Ekwurzel, climatologist at the Union of Concerned Scientists, said the new results confirm earlier studies, including a controversial paper published in July by Kerry Emanuel of the Massachusetts Institute of Technology. Emanuel concluded in the journal Nature that hurricanes in both the Atlantic and Pacific have increased in duration and intensity by about 50 percent since the 1970s. He linked the increase to rising air and ocean temperatures.
"It's like rolling the dice, only we're now rolling loaded dice," Ekwurzel adds. "The good news is that since we are part of the problem, we can be part of the solution."
But not everyone buys the latest study's conclusions.
"The data is just not good enough to conclude that the [Category] 4 and 5s have gone up with this global warming," said William M. Gray, a professor of atmospheric science at Colorado State University and well-known hurricane forecaster.
Even so, he said: "People with a political agenda for human-induced global warming are going to come out of the woodwork and make as much of this as they can."
Although the study's authors say their findings are "not inconsistent" with global warming, the document stopped short of endorsing the connection. That, they said, "would require a longer global data record and ... a deeper understanding of the role of hurricanes in the general circulation of the atmosphere and ocean."
Global warming theorists have predicted the increase in violent storms all along, but until the current study, no one had managed to assemble enough data to reveal what was actually happening with hurricanes worldwide (the storms are called typhoons and tropical cyclones in other ocean basins).
By contrast, Webster said, the natural cycles that climatologists are familiar with - such as El Nino events and an atmospheric phenomenon called the North Atlantic Oscillation - typically affect storms in specific regions.
But critics such as Gray don't buy it. "The major point I think you can take from this study is that, even though the globe has warmed a bit over the last 30 years, the global frequency of storms has not changed," Gray said. "But their main point I don't agree with."
Gray said trends in Category 4 and 5 storms can't be measured accurately because data from the 1970s are unreliable - particularly in remote ocean regions where aircraft measurements were unavailable. Wind speed data there were based solely on human interpretations of cloud patterns as viewed in satellite images, Gray said. Although the technique has improved since, "you certainly couldn't, in the period from 1975 to 1990, distinguish a Category 3 storm that had a pretty good eye from a Category 4 or 5. That just can't be done."
Webster and his research team defended the data, saying that where satellite interpretations have been tested against actually aircraft measurements, they have held up well.But Webster and his colleagues could not explain why rising ocean temperatures have not also driven up the number and duration of hurricanes around the world.
In fact, despite rising sea surface temperatures, they found the number of storms in the western North Pacific basin fell dramatically. And the number of days when storms were raging has fallen by 40 percent since 1995. Asked how this could be, Hudson said, "I would suspect [it] is actually due to natural, short-term variability rather than anything to do with long-term trends" such as global warming.
Ekwurzel said that many factors influence the birth of hurricanes and that most of those don't seem to be changing.
"What's changing is the temperature of the ocean," she said. Once storms are generated, "they're more likely to grow into a monster storm, with severe consequences for coastal communities."
The Georgia Tech/NCAR team was also puzzled by the long-term stability it found in the maximum hurricane wind speeds. Global warming theory predicts that wind speeds at the center of the most intense hurricanes would go up. But they haven't.
"That's not quite in accord with predictions," Holland said. It's "something we need to look into a little bit more."
GRAY: MID-SUMMER UPDATE RAISES THE ATLANTIC SEASON FORECAST
... 20 named storms is an all-time high prediction
From the website posting:
Information obtained through July 2005 indicates that the 2005 Atlantic hurricane season will be an extremely active one. We estimate that 2005 will have about 20 named storms (average is 9.6), 10 hurricanes (average is 5.9), 95 named storm days (average is 49.1), 55 hurricane days (average is 24.5), 6 intense (category 3-4-5) hurricanes (average is 2.3) and 18 intense hurricane days (average is 5.0). We expect Atlantic basin Net Tropical Cyclone (NTC) activity in 2005 to be about 235 percent of the long-term average. The probability of U.S. major hurricane landfall is estimated to be well above the long-period average. This year is expected to continue the past-decade trend of above-average hurricane seasons.
This early August forecast is based on our newly devised monthly forecasts for August, September and October which utilize 55 years of past global reanalysis data. Analog predictors are also utilized. We have increased our forecast from our 31 May prediction due to the seven named storms and the two major hurricanes that have already formed at low latitudes and the increase in favorability of several seasonal predictors over the past two months. This is the highest seasonal forecasts of hurricane activity we have ever made.
GRAY: ANOTHER BUSY ATLANTIC SEASON LIKELY
... 13 named storms, 7 hurricanes predicted
Coming off one of the most active and destructive hurricane seasons on record, famed storm prognosticator Dr. William Gray predicted another above average season on April 1st.
Gray and his forecast team at Colorado State University called for 13 named storms in the Atlantic basin, with seven becoming hurricanes and three of those Category 3 (winds above 110 mph) or higher. Hurricane season begins June 1 and runs through Nov. 30.
"We expect this year to continue the trend witnessed over the last decade of above-average hurricane seasons," Gray said in a statement.
Gray's latest numbers are higher than his initial forecast of 11 named storms, six hurricanes and three intense hurricanes issued in December. El Nino in the Pacific Ocean, a weather phenomenon that can help limit storms in the Atlantic, probably won't be as significant this year as first expected, he said.
That factor, Gray said, may cause him to increase the numbers for his next updated forecast May 31.
The prediction came as parts of Southwest Florida are still recovering from Hurricane Charley, a category 4 storm that ripped through the area Aug. 13, causing $15 billion in total damage. Last year saw 16 named storms, including four hurricanes that pounded Florida during a six-week stretch.
While Gray's forecast cannot pinpoint where or when a storm will hit, Southwest Florida residents shouldn't think last year's unusual barrage will mean more or less storms this season, emergency management officials said.
"It's still early, but from a mental standpoint, we can start preparing now," said Booch DeMarchi, spokesman for Lee County's Emergency Operations Center. "Even if Dr. Gray said there's going to be fewer or more storms, it only takes one."
Warmer ocean surface temperatures - ideal conditions for a hurricane - have been recorded in the Atlantic basin, said Rick Davis, a meteorologist at the National Weather Service in Ruskin. Warmer water can help the breeding grounds for hurricanes, provide better fuel for clusters of thunderstorms and help a storm become better organized, Davis said.
"Last year taught us that we need to have a plan in place right from the start," Davis said. "The chance of a major hurricane hitting the Lee County area is pretty small. Just the fact it got hit last year - it still has the same chance at getting hit year after year."
Gray said there's a 73 percent chance of a major hurricane hitting the U.S. coastline this year. In the last decade, just six of 38 major hurricanes made landfall in the United States. Three of those came last year alone. That number drops to 53 percent for Florida's peninsula, still well above the long-term average of 31 percent, Gray said.
"The 2004 hurricane season was an unusual year," Gray said, "and residents along the east coast should not expect the high number of landfalling major hurricanes ... to be the norm."
HURRICANE DANGERS ON THE RISE?
... Coastal Residents: Look to Higher Ground, Develop Disaster Plan
Hurricane activity has increased and is likely to remain high for a decade or more, the head of the National Hurricane Center believes.
From the 1970s to the mid-1990s the number of hurricanes was low, Max Mayfield told the Senate Commerce Science and Transportation Committee, but now frequency is increasing "and this period of heightened activity could last another 10 to 20 years."
Memories are still fresh of the four hurricanes that battered Florida in 2004. Mayfield said the cyclic increase in tropical storms is made more dangerous because of the growth in coastal populations in recent years. An estimated 85 percent of coastal residents have never experienced a major hurricane, he said.
Mayfield said that even though forecasts and warnings have improved lately, being safe from such storms also requires personal responsibility.
"It really doesn't matter if you make a perfect forecast — if you don't get people to listen to you it's all for nothing," he said.
People in coastal areas need to have a plan and need to know where the nearest shelter is and what the evacuation plans are for their area, he said.
Asbury H. Sallenger of the U.S. Geological Survey added that the lack of experience with storms in recent years has resulted in construction of buildings that may not be able to stand up to them. He pointed out the collapse of a five-story building in Orange Beach, Ala., when it was undermined by Hurricane Ivan.
Of special concern are the Florida Keys and New Orleans, where many people live in low-lying or below-sea-level areas that cannot be easily evacuated, Mayfield said.
"You need to make friends in high places. The problem is, neither of these areas have high places," he said.
Asked about the possibility of vertical evacuation in high-rise buildings in New Orleans, Mayfield said it is a refuge of last resort if people can't be evacuated. After a major storm the power will be out, the water will be out and emergency personnel won't be able to care for thousands of people stuck in high rises, he said.
Overall, hurricanes claim 20 lives and cause $5.1 billion in damage in the average year. Those figures can jump many times in the event of a major storm like Andrew or Hugo.
Dennis McCarthy, director of the office of climate, water and weather services, told the committee that in a typical year there are 1,300 tornadoes in the United States, killing 58 people and causing $1.1 billion in damage. Floods account for $5.2 billion in damage and 80 deaths, he said, while lightning adds 53 fatalities annually.
A recent study indicated that modern Doppler radar has sharply reduced the tornado death toll. McCarthy said the Weather Service is currently investigating radar improvements that could make forecasts even better.
AMERICANS AREN'T PLANNING FOR HURRICANES
... 47% of Respondents Have No Disaster Plan
Most residents along the East and Gulf coasts don't plan to take even simple steps to protect themselves and their homes from hurricanes, despite the devastation caused by five hurricanes that struck the United States last year, according to a 2005 poll.
Fifty-six percent of those surveyed said they felt "not too" vulnerable or "not at all" vulnerable. And one in four would do nothing to prepare for a storm, even after a watch or warning was issued.
In 2004, four hurricanes struck Florida within six weeks. They were among six tropical storms and nine hurricanes that formed during the unprecedented 2004 season. Hurricane Alex also struck North Carolina. Overall, the hurricanes and tropical storms cost 117 lives in Florida and damaged or destroyed one in five Florida homes. Property losses were estimated at $42 billion.
Yet 47 percent of those surveyed had no disaster plan for the hurricane season, the poll found.
"As we look forward, we have to look back," Lt. Gov. Toni Jennings said. "People need to prepare now and they don't have their plans ready and we know it."
Jennings said the most troubling finding was the misconceptions about the steps needed to prepare. A majority of those surveyed — 54 percent — thought masking tape could help stop windows from shattering, which is a myth. And 96 percent didn't know that garage doors were the structural element most likely to fail first in a hurricane.
The poll also found that one in four residents believed they could evacuate flood-prone areas 30 minutes to an hour before a hurricane made landfall.
"That is dangerous folly," said Max Mayfield, director of the National Hurricane Center. Flood-prone roads will likely become impassable, he said. Gridlock also could prevent a last-minute evacuation.
The telephone poll surveyed 1,100 adults from April 20-26 in 12 coastal states from Maine to Texas. It has a margin of sampling error of plus or minus 3 percentage points. The pollsters asked a 20-question test about hurricane related issues. Eighty-nine percent failed the test, and only 2 percent got the equivalent of a C or better by answering at least 14 questions correctly.
"We hope this poll sends up a flare," said Salvation Army Maj. Steve Hedgren.
SCIENTISTS DEVISE NEW HURRICANE FORECAST TOOL
... New model developed at University College in London
British scientists say they have devised a more accurate way to forecast whether the United States is in for a particularly damaging Atlantic hurricane season.
The new computer model, developed by climate researchers at University College in London, measures the intensity of the trade winds and the temperature of the water in July to predict whether it is going to be a busy hurricane season and whether those storms will tend to reach land or stay out at sea.
The researchers reported that the model correctly predicted the unusually active 2004 hurricane season, when Florida and other Southern states were pummeled with five hurricanes in a row — Alex, Charley, Frances, Ivan and Jeanne.
The model was also tested against annual storm data from 1950 to 2003, and correctly predicted 74 percent of the" time whether the number of hurricanes hitting land would be higher or lower than normal, the researchers said. The new method does not predict precisely where storms will strike. But even a more generalized forecast could help protect lives and reduce damage, they said.
Other hurricane forecasters said the method devised by Mark A. Saunders and Adam S. Lea of the Benfield Hazard Research Centre is a sound contribution.
"Their forecast looks to show moderate skill over the past 54 years," said Phil Klotzbach, a research associate with the Colorado State University.
Every year, the Colorado group issues a hurricane forecast for the Atlantic basin based on El Nino activity in the Pacific, drought in Africa and other factors.
In the new method, the researchers measure the irregularities and intensities of winds generated in atmospheric layers ranging from about 2,400 feet to 24,000 feet above sea level in six regions over the North Atlantic and the eastern Pacific. Winds in these regions influence the energy of hurricanes spinning in the Atlantic and steer storm systems toward land.
The researchers found that weaker-than-normal trade winds and warmer-than-normal water favor the formation of intense hurricanes. In 2004, there were 16 named storms, eight of them reaching hurricane strength. The average is about 10 a year, with six becoming hurricanes. The cycle of hurricane strength appears to flip every 30 years and since 1995 active seasons have been the norm.
This year, the Colorado State group foresees 13 named storms in the Atlantic, including three intense hurricanes. The British group will make its 2005 forecast on Aug. 4. Most Atlantic hurricanes that strike land develop after Aug. 1.
2004 ATLANTIC SEASON WAS A DOOZY!
...Florida Repeat is "Unlikely"
Everything about the 2004 Atlantic hurricane season was big -- lots of powerful storms that spawned hundreds of deadly tornadoes, many deaths, an unprecedented onslaught on Florida, a huge damage toll and millions evacuated.
Tropical Storm Otto was born in the Atlantic Ocean on November 30th and forecasters said they reclassified August's Tropical Storm Gaston to Hurricane Gaston.
By the numbers (through 11/30/04), the 2004 season produced 15 storms, nine of them hurricanes. Six were "major" hurricanes with sustained winds of more than 110 mph.
"The amazing thing was only three of the storms did not have an impact on land," said U.S. National Hurricane Center director Max Mayfield. Officials said 9.4 million people along the U.S. Atlantic and Gulf of Mexico coasts came under evacuation orders this season.
Florida took the brunt of the damage in the United States, with hurricanes Charley, Frances, Ivan and Jeanne walloping the state within a six-week span, the first time a single state was hit by four hurricanes in one season since 1886, NHC officials said.
Damage from the four storms may exceed the $25 billion-plus toll of Hurricane Andrew, the killer 1992 storm against which all others in Florida are measured. "Future hurricanes will continue to bring higher and higher damages as long as we continue to develop the coastlines," Mayfield said.
In the Caribbean, Grenada, Jamaica, the Cayman Islands, the Dominican Republic and Haiti sustained serious losses. Ivan damaged 90 percent of Grenada's housing stock, and Jeanne, as a tropical storm, spawned floods that killed about 3,000 people in Haiti, the poorest country in the Americas.
Hurricane Ivan was a nightmare for the oil industry, thrashing through the Gulf of Mexico's most productive oil and gas fields and wrecking platforms and undersea pipelines. Damage from the storm, which helped push oil prices to over $55 a barrel this fall, has so far cut more than 32 million barrels from an already tightly supplied market. That is more than twice the impact on U.S. oil production caused by powerful hurricanes Isidore and Lili in 2002. Producers have still not fully recovered their output, with about 10 percent of their normal production still shut.
Study of Tropical Storm Gaston, which hit South Carolina three months ago, convinced experts that it had achieved the sustained 74 mph winds needed to be classified a hurricane, giving the 2004 season nine hurricanes.
The last decade brought more Atlantic tropical storms and hurricanes than any 10-year period in history. That trend could continue for another two or three decades, officials said.
But for Florida, where thousands of residents are still struggling with cleanup, roof repairs and temporary housing from four hurricane strikes, a rerun of 2004 is highly unlikely.
INCREASING FREQUENCY OF HURRICANES?
...Researchers: "More Hurricanes May be on the Way"
Ivan, Frances and Charley delivered three staggering blows to the Gulf Coast and Florida, as well as Caribbean island nations, all in just five weeks in Aug-Sep 2004. Homeowners ritualistically re-hammering the same plywood over their windows figure it can't get much worse, right?
Brace yourselves: Scientists say 65 million Americans living on the Gulf and Atlantic coasts should expect weather like this for another 30 years. Maybe more. Sure, it's hurricane season and storms happen. But counting Alex, which swamped the Carolinas in August, there were five in six weeks. And that doesn't include tropical storms Bonnie, Gaston, Earl and Hermine. Or Jeanne in mid-September.
"I don't remember this happening before in such a short period of time," National Hurricane Center director Max Mayfield told reporters, "and the season is only half-over."
It might be a generation before hurricane weather slips back into a quiet phase, he and other experts say.
"The hurricane threat is much greater than it was in the 1970s through early 1990s," said federal meteorologist Stan Goldenberg, who flew around Hurricane Ivan in research aircraft as it approached Mobile, Ala. "It could last another 10 to 40 years."
Goldenberg and other experts believe the current hurricane surge is part of an obvious storm cycle that probably has been waxing and waning for hundreds of years.
Roughly from 1970-94, Atlantic hurricane activity in the United States was relatively mild. Sure, there were monster hurricanes like Andrew in 1992 — its 177 mph winds killed 55 people in the U.S. and Caribbean and caused $26.5 billion in damage. Every year a big storm whips up — it's just that most fizzle before veering into a city.
Overall, the 25-year "quiet" period generated about half as many destructive storms as the previous stormy phase dating back to the 1920s, and about half as many as today's stormy phase appears likely to produce.
Since 1995, environmental conditions have shifted and the Atlantic has been spawning more strong storms. The number of major hurricanes has more than doubled. In the Caribbean, it's up by a factor of five.
Even with milder storm years in 1997 and 2002, the period since 1995 is the most active nine consecutive years on record, according to pioneering hurricane forecaster William Gray at Colorado State University.
Since 2000, the United States has been hit by an average of four powerful storms per season. Forecasters have been warning of this for years. Even back in 1998 — a year that saw four hurricanes in September — Gray said: "We are going to see the return of some of these type of storms. People have to face up to it. The insurance industry has a major problem."
Why is the storm cycle intensifying now? Scientists aren't certain what causes the decades-long shifts in the ocean-atmosphere interplay.
Hurricanes reflect the complex dance between the atmosphere and the oceans. When the Pacific Ocean cools during the La Nina climate phenomenon, the Atlantic warms up, and more hurricanes are the result. Over the Atlantic, wind shear that knocks down rising storms tend to slacken, while humid westerly winds from Africa's bulge grow stronger.
Scientists look for large pools in subtropical ocean where water is at least 81 degrees Fahrenheit. The warm sea heats the air in a rising column, creating a center of moist low pressure. Trade winds rush in toward this depression. Combined with the planet's rotation, they spin clouds counterclockwise around this steamy core, or "eye" of the storm. Most scientists agree that global warming plays little or no role in the number of storms in the current hurricane cycle.
Global climate models show that air pollution from industry and traffic will drive up average world temperatures by a degree or two this century. All that extra heat could fuel more stormy weather. And local evidence of temperatures rising may already be apparent with some glaciers melting and spring flowers blooming early. But so far, climate change is too uncertain and today's hurricane patterns are too complex to draw a connection.
"I don't think the warming now is anywhere near enough to account for the increase in hurricanes that we're seeing," said Robert Gall of the National Center for Atmospheric Research in Boulder, Colo. "To me, this is just a natural variation in the frequency of hurricanes."
Hurricanes are among nature's most powerful natural events. Spinning as fast as a race car, the wall of clouds can rise 10 miles into the stratosphere and span 400 miles, as wide as Kansas. The amount of mechanical energy generated by a such a swirling storm translates to a power supply of 360 billion kilowatt hours per day — equal, by some estimates, to all of the electricity consumed in United States in six months.
Only 12 percent of the world's swirling storms spawn in the Atlantic. About 100 of these cyclones are reported annually worldwide. Most of them crank unnoticed in the North Pacific and the Indian Ocean. A large storm might seethe and spin for 3,000 miles, inhaling the energy from billions of tons of warm seawater. Incoming dry air from high pressure zones can choke it off, or landfall can quickly deflate it.
Forecasters are much less comfortable predicting how a storm will behave once it hits land. That's a major focus of their research.
Ivan (Sept 2004) boasted 160 mph winds in the Gulf, but it quickly lost about half of its fury when it reached Alabama. That's not always the case. Hurricane Charley (also in 2004) whipped up to a category 4 storm when it hit Florida's west coast. Andrew was just a tropical storm in the hours before it hit Miami.
Goldenberg said it's harder to forecast storm intensity than to accurately predict its path. Since coastal residents now heed hurricane warnings, researchers are turning their attention to an underappreciated danger — downpours reaching inland for hundreds of miles.
...Forecasters using a new tool to predict rapid intensification
In 2004, hurricane forecasters plan to use a new computer model to help predict whether a storm poses a risk of suddenly intensifying. The rapid-intensity index will determine the probability of a hurricane strengthening by at least 35 mph over24 hours.
Warnings of that type could project a Category 1 hurricane with top winds of 95 mph strengthening to a much more damaging Category 3 hurricane with top winds of 130 mph. But there are limits. The probability index only goes up to 60 percent in the Atlantic basin, and researchers say that high level is achieved only in a few cases. Previously, forecasters could assume only that the chance of a storm intensifying rapidly was about 5 percent.
"You're really going to miss more than you catch," said John Kaplan, a meteorologist for the National Oceanic and Atmospheric Administration's hurricane research division. "But the goal is to get a certain percentage of them which, before this, you weren't going to get. If you can get even 20 percent of the cases, then that's 20 percent more than you would get otherwise."
Kaplan, along with Mark DeMaria of NOAA in Fort Collins, Colo., developed the model based on research over the past five years. Researchers at the Joint Hurricane Testbed on Virginia Key in Biscayne Bay have tested the model for the past three hurricane seasons. Richard Knabb, science and operations officer at the hurricane center, said that during testing, the index worked well on Hurricane Michelle in 2001 but had poor results with Hurricane Lili in 2002 and 2003's Hurricane Isabel.
Early Sept. 7, Isabel had winds of 60 mph far out in the Atlantic. The official forecast called for it to strengthen to about 85 mph in about two days. Exactly 48 hours later, the maximum winds were 135 mph. A few days later Isabel decreased from 150 mph winds on Sept. 15 to 105 mph winds 30 hours later. Its winds had been forecast to decrease to about 140 mph.
Kaplan said he got the idea for the model after Hurricane Opal made landfall on Oct. 4, 1995. When Gulf Coast residents went to bed, Opal was still a slow-moving Category 2 storm. By morning, Opal was a Category 4 hurricane with winds of 150 mph. The storm left nine dead in the United States. Nearly 60 people died outside the United States, most of them in Mexico and Guatemala.
The model uses seven parameters, including ocean temperature and moisture at certain levels of the storm, to determine the likelihood of the storm suddenly strengthening. The hurricane center gets all of the calculations, and then forecasters determine how significant the probability is and whether to use it in a particular forecast.
Hurricane center director Max Mayfield said the new model is just one of many tools forecasters will use, and he warned that this model will not solve the problem of knowing exactly what a storm will do.
"This is going to help a little bit," he said. "We need a lot of help."
MORE ACTIVE EAST COAST HURRICANE SEASONS AHEAD?
...Hurricane cycle means busier storm seasons for East Coast in near future
After Hurricane Isabel, meteorologists are warning East Coast communities to prepare for busier hurricane seasons for the next 10 to 40 years. Higher sea surface temperatures and favorable wind conditions in the Atlantic since 1995 have more than doubled the number of major storms roaring out of the tropics each year. Those affecting the Caribbean have quintupled, and the rare ones that strike in October or later have jumped tenfold.
This is the same confluence of weather forces that spawned a barrage of big hurricanes in the 1950s and 1960s, storms that older Marylanders recall with a shudder. Among the most damaging here were Hazel (1954), Connie and Diane (1955), and Donna (1960).
Hazel brought storm tides 2 to 6 feet above normal to the Chesapeake, with 73-mph winds. It killed six Marylanders, flooded streets around Baltimore Harbor, blew roofs away and floated homes off their foundations.
"If you look back at the 1950s ... it was year after year of these major hurricanes ramming into the East Coast. And we would not be shocked to see that take place again," said Stanley B. Goldenberg, a meteorologist with the National Oceanic and Atmospheric Administration's hurricane research division.
Population increases and intense coastal development since the 1960s are likely to produce a correspondingly higher toll in lives and dollars, he said. Goldenberg was the lead author of a 2001 paper in the journal Science that first noted the return of higher hurricane activity in the Atlantic. The pattern, which began in 1995, is striking - and it has persisted.
"You have to be deliberately blind not to see that something is going on here," he said.
This is not the result of global warming. There is evidence that these long-term hurricane cycles - which can last up to 40 years from peak to peak - stretch at least to the 1600s, Goldenberg said. They're even clearer in the more abundant data gathered since 1900, which show a period of low activity through the mid-1920s followed by higher activity through the 1960s.
But reliable data on Atlantic hurricanes did not became available until 1944, when aircraft - and later satellites - began tracking storms at sea that had previously gone unnoticed. Goldenberg and his colleagues found an average of 2.7 "major" hurricanes a year in the active period from 1944 to 1970. These intense storms have sustained winds above 110 mph - Category 3, 4 or 5 on the Saffir-Simpson scale. Although they constitute 20 percent of all tropical storms, they cause 80 percent of the damage.
In 1970, something changed. The hurricane seasons became much quieter, and the average number of major storms fell to 1.5 per year. There were no Category 4 or 5 storms for 15 years. But in 1995 the pendulum swung back. That year saw one of the most active Atlantic storm seasons on record, with 19 named storms, five of them major. And a pattern was set. The six years from 1995 to 2000 averaged 3.8 major storms per year - even busier than the 1950s and 1960s.
"We don't expect the system to switch back anytime soon," Goldenberg said.
None of this activity is perfectly consistent. Even a busy hurricane era will produce slow years, Goldenberg said, just as the "low-activity" era that ended in 1994 produced some ferocious storms. Those included Andrew, which devastated south Florida in 1992, and Hugo, which battered Charleston, S.C., in 1989.
BR>Nor will every hurricane season during an active era produce East Coast landfalls. Goldenberg said Eastern states have been shielded by a persistent atmospheric pattern that has steered many storms out to sea.
But "we expect things to shift," he said. Florida was a frequent target in the 1940s, before the bull's-eye shifted to the East Coast during the 1950s and to the Gulf Coast in the 1960s.
Isabel and Fabian, which raked Bermuda with 120-mph winds Sept. 5, were "among the top five, longest-lasting intense hurricanes of all time," said Phil Klotzbach, a research associate at Colorado State University's Tropical Meteorology Project. The project is headed by William Gray, a co-author of the 2001 paper in Science.
Isabel was a Category 3 storm or stronger for eight days, spinning in a perfect, terrifying spiral. "It was the best-looking storm I've ever seen in the Atlantic," Klotzbach said. "Thankfully, by the time it made landfall it had weakened a lot. You wouldn't want to see what would happen if it came ashore like that."
One key ingredient is high sea-surface temperatures, which provide the energy and instability needed to spawn storms. Another is low "wind shear," a measure of the difference in speed and/or direction between winds near the surface and those 40,000 or 50,000 feet up.
"A hurricane has to organize in the vertical, like a chimney," Goldenberg said. "If you have strong differences, you knock the chimney over."
Andrew was a struggling tropical storm that was being "decapitated" by wind shear as it approached Florida in 1992. "But as soon as the shear relaxed, Andrew snapped to and rapidly intensified from a tropical storm to a Category 5 in 36 hours," Goldenberg said.
The storm crashed ashore in Florida and demolished much of southern Dade County where Goldenberg, his children and thousands of others clung to the wreckage of their homes. "I'm not some scientist in some ivory tower saying this stuff," he said.
In their paper in Science, Goldenberg, Gray, Christopher Landsea and Alberto M. Mestas-Nunez pointed out decades-long cycles in sea-surface temperatures and wind shear in the tropical Atlantic. Those factors closely matched the cycle of major hurricane formation.
But there are other players in the cause-effect game. Over the past decade, meteorologists have tied warm-water El Nino conditions in the eastern tropical Pacific to increases in vertical wind shear in the Atlantic. That wind shear has tended to suppress the formation of major hurricanes.
In 1997, the strongest Pacific El Nino of the 20th century emerged in the midst of the resurgent Atlantic activity that had prevailed since 1995. The Atlantic hurricane season fizzled that year. It fizzled again when a weaker El Nino returned last year.
While most meteorologists have accepted the existence of a hurricane formation cycle that spans decades, there is less unanimity about what drives it.
The most prominent theory, espoused by Gray and others, is something called the "thermohaline circulation." This is a global current - a sort of oceanic conveyor belt driven by changes in temperature and salinity - that speeds up and slows down in cycles of roughly 25 years. When that circulation is strong, Goldenberg said, the North Atlantic - including the hurricane regions - warms up. When the flow weakens, the water cools.
"Not everybody is in agreement on that," he said, "but the Atlantic multidecadal mode [the hurricane cycle] is very clear, and its effect is very clear."
Coastal residents and emergency managers need to be prepared, Goldenberg said. "We can expect to see continued deadly hits in the Caribbean, a continued increase in overall activity and more landfalls than even we've been seeing on the East Coast."
Scientists can't predict exactly when the East Coast will again come under more persistent assault from the tropics, he said: "Maybe now is the beginning of it."
SENSORS MAY YIELD MORE HURRICANE ANSWERS
...data collected by gadgets called 'sondes'
The strongest winds of a hurricane are in its eyewall, the swirling complex of clouds and rain that rotate around the eye of the storm. Until recently, only a few measurements had been made of the force these huge winds exert near the ocean's surface, an important element in determining the intensity of a hurricane. Instead, forecasters estimated the strength of the wind under the eyewall when they predicted hurricane effects like storm surges.
Now, using data delivered by gadgets that can withstand a hurricane eyewall, a team of researchers has measured in detail the wind's speed at different altitudes at times when there are high winds near the ocean's surface.
The researchers, lead by Dr. Mark D. Powell of the National Oceanic and Atmospheric Administration's hurricane research division in Miami, analyzed data collected in 15 hurricanes by more than 300 of the windproof devices, called dropwind sondes or sondes. The small, instrument-packed cylinders, each equipped with a parachute, were released into the eyewall from planes flying at altitudes up to 10,000 feet. The sondes radioed measurements every half second to the plane until they landed in the ocean.
The data collected by the sondes - mostly in the Atlantic, the Caribbean and the Gulf of Mexico - may lead scientists to revise their models for hurricane intensity. "We've never had any measurements in high winds over about 50 knots to see how the wind changes when it's very close to the surface," Dr. Powell said. Instead, scientists extrapolated values based on weaker wind speeds.
Now the new findings suggest that some of these extrapolations were wrong. "We've always thought that drag or resistance increases with sea surface roughness and wind speed," Dr. Powell said. But when the team analyzed the sonde data, they found that the ocean caused less, not more, resistance in winds above hurricane force.
James L. Franklin, a hurricane forecaster at the National Hurricane Center in Miami, helped design the sondes that gathered the data for the study and has himself published on hurricane structures revealed by drop-sonde data. The battery-powered gadgets, which cost about $550 each, are equipped with Global Positioning System modules, as well as sensors to measure temperature, pressure and humidity. The instruments within the sondes transmit to the plane twice a second as they fall.
"Since the sonde is falling at about 30 feet per second," Mr. Franklin said, "you get data every 15 feet, meaning very detailed information."
As the sonde, supported by its parachute, is carried along with the wind before it hits the ocean, "the G.P.S. tells us how fast the sonde is moving," he said, "so that if we measure sonde motion, we are at the same time measuring air motion."
The sonde's electronics board includes a microprocessor that receives the raw information from its sensors. It processes the signals and sends them to its transmitter, which radios the information to the accompanying plane. From the plane, scientists like Mr. Franklin monitor the data before sending it to a computer at the National Weather Service in Washington. "From there,'' Mr. Franklin said, "the data are relayed to the National Hurricane Center and then distributed globally" so that forecasters can use the information immediately in their projections.
The transmission time from hurricane eyewall to forecasting center is brief. "From when the sonde is kicked out of the airplane until we receive the data at a forecast center, it's only 10 to 15 minutes," Mr. Franklin said.
Gary Barnes, a professor in the department of meteorology at the University of Hawaii, said that the sonde study showed what could happen when people bring new instruments to an old problem. "Often a few good measurements will derail an accepted theory," Dr. Barnes said, "or at least trigger major modifications."
He predicted that the data would cause scientists who simulate hurricanes to revise their calculations.
"If the drag coefficient is lower than what was assumed under and near the eyewall," he said, "then we are losing less wind energy to the sea." That would mean that winds are higher at the surface than was generally assumed. "If the drag coefficient is less, then our standard ways of estimating heat and evaporation from the sea surface need to be reconsidered," he added.
Dr. Powell and others think that the ocean's foam may cause the surface to become smoother rather than rougher at extreme winds. "The wind just blows the tops of the waves off," Dr. Powell said, "injecting spray and more and more air into the ocean."
By the time the winds surpass 100 knots (about 115 miles per hour), producing waves of 30 feet and more, the ocean surface is completely covered by spray or foam. "We think it is the foam that is affecting the transfer of momentum between the atmosphere and the ocean," he said, as the sea surface no longer acts as a brake for the wind.
Dr. Barnes agreed that spray might affect hurricane intensity. "It may be a critical component that is just beginning to be understood," he said.
Dr. Powell pointed to one limitation in the study: virtually all the data that formed the basis for the report were collected over the open ocean. The sondes weigh a bit less than a pound and are rarely released over land because they could cause damage as they fall from the sky. "The results are really only valid for storms that are far from the coastline," he said.
Dr. Powell said that he would be working with the National Hurricane Center and the Air Force to develop ways to release sondes along the coastline when storms approach. He does not plan to be on board to help, though, as the sondes are tossed from planes. "My stomach doesn't do too well," he said.
STUDY: RESURGENCE IN NORTH ATLANTIC HURRICANE ACTIVITY
...Scientists: Future Atlantic hurricane picture highly complex
In a highly publicized article in the journal Science, a team of meteorologists predicted that the current resurgence in North Atlantic hurricane activity will continue for at least the next 10 to 40 years. That may indeed be the case, say two hurricane researchers at North Carolina State University. But it's only a small part of a complex tropical storm picture facing the U.S. Eastern Seaboard.
Those NC State meteorologists and oceanographers, Dr. Lian Xie and Dr. Leonard Pietrafesa, have used a recently developed mathematical technique to analyze patterns relating to the tropical cyclones that made landfall along the East Coast between 1887 and 1999.
Their findings: The number of hurricanes making landfall in a given year is controlled not only by the long-term, multi-decade trend described in the Science article, but by three shorter-term cycles as well. These four distinct "temporal modes" - each probably the result of a different atmospheric and oceanic phenomenon - combine to determine the number of tropical storms that make landfall each year, Xie and Pietrafesa explain.
"It's the short-term modes that have the most effect on the number of Atlantic tropical cyclones that make landfall each year," Xie said. "There's a danger if you don't look at all the modes, not just the longest-term mode."
Pietrafesa adds that while the long-term cycle contributes about one or two tropical cyclones per year to the total, the shorter-term cycles typically contribute up to five in a given year for the entire North Atlantic, several of which hit the coast.
The North Atlantic has seen dramatic hurricane activity since 1995, with powerful storms like Hurricanes Fran and Floyd pounding the eastern United States and resulting in many lost lives and extensive property damage. The authors of the article - Drs. Stanley B. Goldenberg and Christopher W. Landsea of the National Oceanic and Atmospheric Administration, Dr. Alberto M. Mestas-Nunez of the University of Miami and Dr. William M. Gray of Colorado State University - suggest that the recent upswing in the number of hurricanes is the beginning of a 20-50 year trend characterized by an increased number of hurricanes.
Xie and Pietrafesa believe that their mathematical analysis technique, called Empirical Mode Decomposition (EMD), more accurately describes the temporal patterns of tropical storm occurrences along the East Coast than the procedure used by Goldenberg and his colleagues.
EMD mathematically analyzes the differences in the number of tropical storms occurring over different time scales, resulting in a series of wave-like graphs describing cycles in the number of landfalling tropical cyclones. Using EMD, Xie and Pietrafesa found four different cycles, or modes.
The number of tropical storms that make landfall in a given year depends on whether each of the four cycles is at its peak, its low point, or somewhere in between. The highest number of hurricanes is likely to occur in years during which most or all of the cycles are "in phase" at their peaks.
The most energetic cycle - the one that shows the greatest variation in the number of landfalling storms between its peak and low-point - is one that lasts three to five years. That cycle, Xie says, essentially adds or subtracts one or two landfalling tropical storm events every year on the East Coast.
The eight-to-12-year cycle can add or subtract an average of one and a half hurricanes per year; the 20-40-year cycle can add or subtract an average of about one-half hurricane per year; and the longest, 40-60 year cycle (similar to the cycle described by Goldenberg and his colleagues) can add or subtract about one hurricane per year.
"The longer-term cycles indicate that in the early 21st century, higher-than-normal landfalling tropical cyclone activity is likely to occur along the eastern United States coast, and in North Carolina in particular," Xie said. "The causes of these decadal trends are not yet clear, but may be related to multi-decadal oscillations of ocean circulations in the Atlantic and Pacific Oceans."
Those oscillations, he said, include the long-term weather events known as El Nino, which is linked to the periodic warming of the Pacific Ocean off the coast of South America, and La Nina, which is the cooling of those same waters.
During the 112-year period for which the NC State researchers have data, an average of 3.23 tropical cyclones pounded the East Coast each year. During El Nino years, that number dropped to an average of 2.47 storms. North Carolina saw an overall average of 0.81 tropical cyclones annually, and 0.56 during El Nino years.
The EMD technique was developed by former NC State oceanic engineering professor Dr. Norden E. Huang, who is now senior fellow and chief scientist for oceanography at the NASA Goddard Flight Center in Maryland.
Xie and Pietrafesa note that scientists still have a great deal to learn about what causes fluctuations in the number of hurricanes, especially over the short-term. "The ability to predict the number of hurricanes for a given year is improving, but we're not there yet," Pietrafesa said.
Their research was funded by the Office of Naval Research and the National Oceanic and Atmospheric Administration.
THE HEBERT BOX
...a generally reliable hurricane indicator
If Floridians want an early, generally reliable indication of whether an intense hurricane is destined to bang on their front door, they should keep an eye on the Hebert Box.
Discovered by a veteran meteorologist, the Hebert Box is a relatively small section of ocean touched by almost every Atlantic storm 1900 that struck South Florida as a major hurricane. If a Category 3, 4 or 5 storm in the Atlantic never touches the region bordered by latitudes 15 and 20 degrees north and longitudes 60 and 65 degrees west, it virtually always misses South Florida. And if one of those storms, with winds higher than 110 mph, touches that region ...
"Really, really pay attention," said Paul Hebert (pronounced HAY-bear), a former forecaster at the National Hurricane Center who discovered the phenomenon.
For what it's worth: Dean was born Wednesday just outside the Hebert Box. The storm fell apart. Still, experts said, South Floridians must pay attention to every tropical-weather system.
"It would be foolish to think that a major Atlantic hurricane could not hit the Miami area if it did not go through the box," said Max Mayfield, director of the National Hurricane Center.
Example: The 1935 Labor Day hurricane that ravaged the Florida Keys as a Category 5 monster, killing hundreds. It never touched the Hebert Box. Still, special attention should be paid to storms that move through the box. It is a matter of geography and climatology,scientists say.
When storms come through the box, they still have space and time to develop into strong hurricanes before reaching Florida. When storms miss the box, they often are too close to Florida to intensify. Or they are so far away that they are vulnerable to forces that pull them across the Caribbean, crash them into the mountains of the Dominican Republic, Haiti or Cuba, push them north of Florida or bend them toward the open ocean.
The 335-mile-by-335-mile area encompassed by the Hebert Box includes the U.S. Virgin Islands and other Caribbean islands, but not Puerto Rico.
The Hebert Box should not be confused with a much larger "box" -- extending from the Gulf of Mexico to the Dominican Republic -- designated by insurance companies. When a storm enters that zone, insurers stop writing new policies in Florida and upgrading existing policies.
The pattern identified by Hebert has persisted since 1900 and has proven accurate for nine of 10 storms that developed in the Atlantic and struck Miami-Dade, Broward and Palm Beach counties as major hurricanes, he said.
MONSTER HURRICANES IN OUR FUTURE?
...Climate shift is turning Atlantic into a hurricane freeway
Weather researchers think the evidence is now clear: A major shift in the climate has taken place that has brought about an increase in major hurricanes. The period of heightened activity could last for decades, and unleash a catastrophic storm on the United States, according to meteorologists.
Since the climate shift began six years ago, when the Atlantic Ocean began looking like a hurricane freeway, the number of hurricanes that have formed in the Atlantic basin has doubled, said scientists at the U.S. Hurricane Research Division. The number of major hurricanes, which produce winds in excess of 110 miles an hour, has also increased during the period by 250 percent, they said. The increased activity will continue for the next ten to 40 years, which could mean trouble for the United States.
"Most seasons we are going to get a hurricane hit the U.S. and probably more than half the time we will have a major hurricane hitting the U.S. as well," said hurricane meteorologist Chris Landsea.
Already hurricanes have increased in number and intensity. Since 1995,the Caribbean has been pounded by deadly storms like Mitch, Lenny, Marilyn, Luis and Georges. Spared the brunt of the storms, the United States has simply been lucky so far, the scientists warned.
"With the increased number, if it starts pounding the U.S., as we feel like it is going to happen, there's bound to be a major city impacted and we could be talking about a real disaster of epic proportions on our hands," said hurricane meteorologist Stanly Goldenberg.
A hurricane causing $50 billion in damage and hundreds to thousands of deaths is quite possible in the next ten or 20 years, according to Landsea.
"I think at this point the U.S. is so developed and there's so many people along the coast that just about anywhere is a major disaster ready to happen."
Scientists say the Earth's climate goes through cycles, but they don't know why. Right now, Atlantic water temperatures are slightly warmer than usual, by just half a degree Fahrenheit. And in general, there is less wind shear.
The current conditions resemble those in 1900 when Galveston, Texas, was nearly obliterated, and the time between the 1920s and 1960s when hurricanes repeatedly slammed into Florida and the disastrous Yankee Clipper hit New York. The period from 1965 to 1995 saw opposite conditions, cooler water and more wind shear, neither of which fosters hurricane development.
Times have changed. From Florida to New England, everywhere along the East Coast is now at increased risk of a major hurricane, the scientists said.
COMING ATTRACTION: EXTENDED HURRICANE FORECASTS
...Forecasters to test their accuracy on 5-day hurricane predictions
The moment a hurricane forms in the Atlantic, coastal residents wonder: where will it hit? Usually, the endangered area remains unknown until the storm is two or three days away.
By as early as next year, officials at the National Hurricane Center hope to offer four- and five-day forecasts of a hurricane’s track and potential landfall points. They’re already working on such long-range forecasts but on an experimental basis for in-house databases. "At the end of the season, we’ll take all the five-day forecasts and see what kind of performance we have," said hurricane specialist Miles Lawrence. "That’s the purpose of keeping it in-house: to see if there’s any value to these forecasts."
Currently, the hurricane center in Miami-Dade County starts providing forecasts when a system is three days away. The forecast is updated every six hours and anticipates where a storm will go when it’s 48, 36, 24 and 12 hours out. When a system is expected to approach within 36 hours, tropical storm or hurricane watches are posted. If a storm might hit land within 24 hours, warnings are posted.
NEW TECHNIQUES FOR HURRICANE SEASON
...New methods being tried this season
Thousands of people sat in traffic jams along the southern Atlantic coast, fleeing a hurricane that wound up not even coming close to their homes. Last year, forecasters predicted a horrendous hurricane season. But when it was over, not a single storm had made landfall in the United States. But the forecasters have a message for doubters: Give us another chance. We're getting better all the time.
Weather experts expect some new methods to produce vast improvements this year in tracking hurricanes and predicting their intensity. NASA jets will be dropping measuring devices into storms from above, and flying robotic drones could be measuring hurricanes from below.
"It's really a kind of revolutionary time in our field," said Joseph Cione, a hurricane meteorologist at the Atlantic Oceanographic and Meteorological Laboratory in Miami. "This has the potential to really answer a lot of questions."
Among the new methods and gadgets the National Weather Service plans to put to use this year is a "coupled model" that studies the ocean as well as the atmosphere to track and measure storms. Researchers now believe warm ocean temperatures feed hurricanes. But as hurricanes spin in place, they cool the waters below them and become weaker.
"Until this year, that effect wasn't in our hurricane model," said Morris Bender, research meteorologist at the federal Geophysical Fluid Dynamics Laboratory at Princeton University. "As a result, it caused our model to overpredict how strong storms are going to get."
Isaac Ginis, an oceanographer at the University of Rhode Island, pioneered the line of study and said the coupled model should improve intensity predictions by 30 percent.
Another important change this year is in the weather service's global analyses. Four times a day, the agency takes information from satellites, weather balloons and other sources, and creates a snapshot of the world's atmosphere. The weather service got approval this month on changes that should help computers use that data to better simulate hurricanes moving across the ocean's surface. Bender said the changes have allowed him to decrease his "track error" by up to 10 percent, or 20 miles. More precise tracking can mean huge savings: Officials estimate it costs an average of $1 million for every mile of U.S. coast evacuated.
NASA and the National Oceanographic and Atmospheric Administration both plan to have two planes aloft this season, studying hurricanes top to bottom. Pencil-shaped devices ranging from 1 to 3 feet in length will be dropped into the storms to measure everything from wind velocity and moisture to water temperature and salinity.
An Australian company also is seeking permission from the Federal Aviation Administration and Center for Aerial Reconnaissance to fly pilotless robotic planes into this year's storms. The Aerosonde Ltd. drone weighs about 31 pounds and has a wingspan of 9 1/2 feet. It launches from a car's roof rack and can carry 4½-pounds of high-tech measuring equipment.
Maurice Gonella, Aerosonde's principal engineer, said the $100,000 drones can be put on autopilot and will constantly relay information and take photographs. "To get an aircraft to fly, say, at 1,000 feet for 24 hours is a huge task, whereas an unmanned drone can do that easily," he said.
Hurricane experts are also working on extending their forecasts. The weather service currently makes hurricane projections no more than 72 hours out. The agency is experimenting this year with five-day forecasting, but the results will be kept in-house for now.
"The goal is ... if we do this, and it turns out that we're good at it, that we would make these forecasts public in 2003," said James Franklin, a specialist at the National Hurricane Center in Miami.
Dire predictions of a massive storm surge from Hurricane Floyd in 1999 prompted the largest peacetime evacuation in U.S. history. Interstate highways from Florida to North Carolina were locked in what became a regionwide traffic jam.
"A lot of people didn't evacuate from places they should, but there were other places where people were leaving from safe areas," said Jay Baker, vice chairman of the National Hurricane Conference.
As more and more people build closer and closer to the coast, forecasters hope advancements in their field can keep them ahead of the curve.
"It's hard to know any breakthrough," said Colorado State's William Gray, one of the nation's leading hurricane researchers. "But there has been advancement across the board. It's down-and-dirty data that you can work with, and you make progress."
WHAT IS FUELING HIGHER HURRICANE ACTIVITY?
...Expert says warming is not the culprit
Despite new research that appears to show the world's oceans are warming because of greenhouse gases, that's not what is fueling a new era of higher hurricane activity, said William Gray, one of the world's foremost experts on tropical weather.
"Global warming is a red herring," said Gray recently. "We have much more to fear from nature than we do from ourselves."
The real answer probably is found in the Atlantic Ocean's salinity, said Gray, a Colorado State University professor known worldwide for his annual predictions of hurricane activity.
The Atlantic Ocean's salinity levels are key to a phenomenon called the thermohaline circulation, a global-scale conveyor belt of marine water. Because water with high salt content is heavier than surrounding water, it sinks to great depths and sets in motion massive underwater currents.
When the circulation system moves swiftly because of high salt content, more storms occur, said Gray, whose conclusions were based on analysis of decades of North Atlantic sea temperatures and hurricane activity. Sea temperatures are an indirect signal of salt content, Gray said.
Tied to other atmospheric and ocean characteristics, the thermohaline circulation may help explain decade-long trends in major Atlantic Basin hurricanes. Gray's theory is new, even to meteorologists who specialize in hurricane predictions and research.
One thing tropical-weather forecasters are fairly certain of is that the Atlantic Ocean, Caribbean Sea and Gulf of Mexico have entered a new, more active hurricane era. Since 1995, there have been 79 named storms and 49 hurricanes. It is the most active six-year period dating back to 1886.
"We'll undoubtedly see more major land-falling storms in the next 10 to 20 years," Gray said. "And we'll see much more damage because there is a greater population living on the coasts now. It's inevitable."
Gray updated his annual hurricane forecast in April to include 10 named storms with six hurricanes, which reflects a slightly more active season than previously expected because of some new ocean measurements that favor tropical-cyclone formation.
...Many coastal residents unprepared
Weather officials fear most coastal residents are unprepared to deal with the dangers of the monster storms. According to a study commissioned by the American Red Cross, 50 percent of the 48 million U.S. coastal residents are not concerned about major storms. Only 41 percent have an evacuation plan and, of those, only 22 percent have explained it to their children. Sixty percent haven't thought about where they would evacuate their families. The study surveyed about 2,000 residents living in coastal areas from Texas to Maine.
... Texas A&M To Unveil New Mobile Radar System To Track Tornadoes, Measure Hurricane Winds
(Source: Texas A&M Univ.) How fast is a hurricane usually blowing when it makes landfall? Researchers still don't know for sure. Current wind speeds for hurricanes over land are estimates based on the damage they leave in their path. But all that will change in April 2001, when Texas A&M University unveils its new mobile radar system, SMART-R.
SMART-R stands for Shared Mobile Atmosphere Research and Teaching Radar. The project involves building two Doppler radars, each on its own 33 foot long trailer. The entire rig -- trailer, pedestal and radar dish -- will stand 14 feet high, and the antenna dishes themselves will be eight feet in diameter.
The large antenna will focus more energy for better resolution, allowing us to detect smaller storms, like tornadoes. If they were any larger, however, they couldn't go down the road. The whole driving force behind SMART-R is that it's mobile.
A joint project of Texas A&M, Texas Tech University, the University of Oklahoma, and the National Severe Storms Laboratory (NSSL), the dishes are being built in the basement of the geosciences building on the Texas A&M campus, while the NSSL is outfitting the trailers at its headquarters in Norman, Okla. Both trailers and mounting pedestals must be specially designed to be strong enough to withstand the tremendous loads generated by high winds hitting the big dishes.
In March, a crane will hoist the dishes and mount them on the trailers. Once the dishes are on the trucks, they will be taken down to Florida during August and September -- peak hurricane season -- for their first major field test.
Although SMART-R is especially designed to image the precipitation and winds that occur within any strong storm, including tornadoes, microburst, and horizontal windstorms, its real advantage will be in allowing researchers to track hurricanes once they hit land.
When hurricanes are over water, chase planes equipped with Doppler radar can fly into them and take wind speed and other measurements. But once a hurricane hits land, it spawns multiple tornadoes, making conditions too dangerous for weather planes to fly in. SMART-R can be placed off to the side of the hurricane's initial landfall zone, as much as 50 to 100 miles away, and measure at a distance the hurricane's wind field over a broad area. Computers mounted in the cabs of the mobile radar trucks will contain software to analyze and archive the radar data.
More people die from the inland floods that accompany hurricanes than from the winds themselves. SMART-R will enable tracking the evolution of hurricane's changing wind patterns and predict how much rain to expect. SMART-R rigs can be deployed with only three days advance notice, from Texas to South Carolina. The mobility of having the radar dishes on trucks will make such quick response possible.
The Gulf Coast has suffered hurricane and tornado damage on many occasions, such as on June 17, 1997, when 190,000 Houston homes lost power due to severe straight-line winds on that day.
On that occasion, the storms were small and evolved rapidly. There weren't enough radars close enough together to allow making accurate predictions. SMART-R, with its rapid deployment, will permit connecting enough data to make better forecasts and warn people earlier of approaching storm danger.
Older technology, such as cars equipped with sensors to measure winds and barometric pressure and weather balloons released from vans, did not give meteorologists enough information to accurately predict when high winds would occur on the surface of the ground. Old algorithms generated up to an 80 percent false alarm rate, with only a 40 percent prediction success.
There have been radars on trucks before. But no one has gone to so much trouble to make them as rugged as SMART-R will be.
IN REVIEW: A RELATIVELY CALM 2000 HURRICANE SEASON
...Hurricanes Spared U.S. in 2000; above-average activity
This year, the nation's Atlantic and Gulf coasts were spared the wrath of a hurricane for the first time since 1994. Two tropical storms - Gordon and Helene - hit Florida in September, causing about $26.8 million in damage but no deaths or injuries. The last time the United States was not hit by a hurricane was six years ago, when the same list of names was used for storms.
"The overall activity was above normal," said a specialist at the National Hurricane Center in Miami.
Overall there were 14 named storms during the 2000 season: eight hurricanes and six tropical storms. The average is 10 named storms per year. Tropical Storm Gordon slammed into the state's Big Bend area in mid-September just hours after being downgraded from a hurricane. Tropical Storm Helene hit the Panhandle a few days later. Both storms dropped heavy rain, blew shingles off roofs and caused road damage and beach erosion.
In August, Hurricane Debby caused a false alarm when computer models projected the storm would hit the Florida Keys. All non-residents were ordered off the chain of islands two days before the storm was supposed to hit. The hurricane dissipated as it veered south of the Keys and into the Caribbean Sea. A month later, Hurricane Keith ravaged Belize, Nicaragua and parts of Mexico. At least 12 deaths were reported.
...Ocean currents may intensify hurricanes
Experts who track the path and intensity of hurricanes in order to determine when to issue evacuation warnings are now looking at how a flow of warm water called the Loop Current may impact the strength of the storms that cross it.
"All evacuations are based on hurricane intensity, but while we can track hurricanes pretty fairly, forecasting the intensity of hurricanes is more difficult," says Nick Shay, a hurricane researcher from the University of Miami.
Hurricanes get their fuel from the warm surface water of the ocean. The storms dissipate when they move inland away from their warm water energy source, or when winds churn up the surface water and allow the undersea layers of low-energy cold water to reach the surface.
The Loop Current, however, includes warm water running at deeper depths, and therefore packs the kind of energy that can theoretically intensify a hurricane from a relatively weak Category 1 to a dangerous Category 4 or even a Category 5 storm in a matter of hours, leaving coastal residents who had been planning to ride out a modest storm little time to escape from a potential killer storm.
Determining the level of the Loop Current's influence on hurricanes should make it easier for forecasters and government officials to decided if and when to give the order to evacuate.
"Intensified hurricanes can effect millions who live in coastal areas," said Peter Black, of National Oceanic and Atmospheric Administration's Hurricane Research Division. "All evacuations are based on the forecast of intensity."
A minimal Category 1 hurricane has winds up to 95 mph and storm surges of up to 5 feet. While trees and other outdoor vegetation are damaged, buildings generally are not. A catastrophic Category 5 hurricane, such as Camille in 1969, packs winds of more than 155 mph and a storm surge of 18 feet; in such a storm, trees are blown down, buildings are damaged and evacuations are ordered.
Shay and Black are working on a $500,000 federally-funded study for the Weather Research Project to collect data and measurements concerning the Loop Current and hurricanes.
"We believe the Loop Current intensified Hurricane Opel (in 1995) and several others," Black said. "Normally, warm ocean water is about 1-meter deep and it is this warm layer of water that provides hurricanes with its energy and moisture, but the Loop Current is much deeper."
The Loop Current runs 100-200 meters deep and is more than 100 meters wide. It flows between the Yucatan Peninsula of Mexico and Cuba, curls to the right of the Western Florida shelf, turns left through the Straits of Florida and then flows northward into the Gulf of Mexico. In addition to tracking the Loop Current, researchers must also track the current's eddies.
"Eddies, or currents of water that move contrary to the direction of the main current, are shed from the main current every 11 months on average and drift into the Gulf of Mexico," explained George Maul, of the Florida Institute of Technology, in Melbourne, Fla.
Black and Shay pointed to last year's Hurricane Bret, which jumped from a Category 2 to a Category 4 in the span of a few hours. The scientists say they suspect a hidden eddy just off the coast of Texas was the culprit.
"Understanding how the Loop Current impacts a hurricane would also impact those living on the East Coast," explained Maul. "The Gulf Stream that moves up the East Coast is also a deep warm current."
Black, who has been flying with the Hurricane Hunters, NOAA's airborne fleet of tropical storm specialists, has been conducting measurements before and after hurricanes. The researchers take measurements of ocean density, salinity and water mass as well as the temperature of the water at different depths. The data gathered by the researchers is used then to validate data coming from satellites.
"What's made this research possible is the satellite measurements," said Black.
The satellite can pinpoint and measure the Loop Current because the warm water appears as a bubble - warm water expands - on the ocean, and the satellite picks up deviations of 10 centimeters on the ocean surface. The satellite goes over the same areas every 10 days to update the data.
Shay called the influence of the Loop Current a "no-brainer," adding that "we have a pretty good clue this is what's happening in up to 20 percent of the storms - it's more than a coincidence."
HURRICANES ARE MORE DEADLY INLAND
...Study looks at fatalities since 1970
Although they have long been feared as coastal killers, hurricanes have killed far more Americans inland than along shorelines since 1970, according to a study released in Septemebr 2000.
Of the 600 U.S. hurricane fatalities since then, 59 percent of the victims drowned inland in fresh water, often in their cars, according to Ed Rappaport, deputy director of the National Hurricane Center in Miami. His analysis appeared in the September issue of the Bulletin of the American Meteorological Society.
Before 1970, storm surge -- the abnormally rapid and high rising of the sea that swamps the coast -- had been hurricanes' No. 1 killer, accounting for 90 percent of 25,000 recorded U.S. fatalities. In the last three decades, Rappaport found, storm surge claimed only six of the 600 lives lost. The real killers since 1970 have been slow-moving storms with relatively weak winds but lots of rain.
``At the same time that we've made progress and had some luck in our efforts against storm surge losses, we've had continuing casualties in inland areas from freshwater floods,'' Rappaport said.
The floods are turning cars into death traps, Rappaport found. He counted 138 victims -- including 32 of the 56 fatalities in Hurricane Floyd last year -- drowned in their cars or while attempting to abandon them. Inland flooding is a major concern for the weather service because most of the East Coast is saturated from an extremely wet summer and the actual peak of hurricane season is Sept. 9 and 10. In response, government agencies have started to emphasize to the public that hurricanes aren't just a coastal problem.
``We need to improve our public education on this,'' said Federal Emergency Management Agency chief of staff Jane Bullock. ``No matter where you live (in the eastern United States), a hurricane can effect you.''
DEBBY: LESSONS LEARNED
...Storm's demise throws experts a puzzling curve... Computers are accurate, but don't know everything
Hurricane forecaster James Franklin tossed and turned in bed until he figured out what all 15 computer models missed about Hurricane Debby:
Overly eager to produce mayhem, the lower half of Debby outran the protective upper half, leaving the storm vulnerable to crosswinds that finally killed it. It turns out that none of the highly sophisticated computer programs were sophisticated enough to predict that. Have the models learned their lesson?
''The models don't learn,'' Franklin said. ``It's more important that we learn.''
Relying on those models, forecasters predicted that Debby could strike South Florida. Residents prepared for trouble and emergency managers ordered 15,000 tourists out of the Florida Keys. Everyone performed properly, most experts agreed, and it all turned out wrong -- thank goodness -- and it was largely the fault of those bits and bytes of data in the models.
``Things that go on inside a hurricane can happen on a small scale,'' Franklin said. ``Models sometimes have trouble seeing the inner part of a hurricane. The state of the art is just not there yet.''
Forecasters officially declared Debby dead on August 24th and the Keys invited its evacuated tourists to return. The remnants of Debby comprised nothing more than a tropical wave that dropped lots of rain on Cuba, Jamaica and Haiti.
But forecasters kept an eye on it. Some models predicted that it would redevelop over the Gulf of Mexico, and the models usually are fairly accurate -- if you discount pretty much everything they predicted about Debby.
Last year, when Hurricane Floyd prowled closer and closer to South Florida, the models said it would turn away at the last minute, and forecasters agreed. Floyd did turn away, just as predicted. But this time . . . whoops.
Hurricane forecasting is part science and part art, but hurricane forecasters are scientists at heart and they don't like it when the data tell lies.
``The models were in great agreement about Debby,'' said Max Mayfield, director of the National Hurricane Center in west Miami-Dade. ``What we do is very complicated, but we always have to give a lot of weight to the data.''
Researchers will spend many months this winter working on those answers, but Franklin thinks he knows where to start:
The models overestimated the potency of Debby, believing it had sufficient power to survive its encounter with the mountains of the Dominican Republic. More importantly, the models failed to predict that Debby would move west faster than a high pressure zone that sat atop the hurricane at about 45,000 feet. Like an umbrella, the high pressure zone protected the hurricane's cloud tops from crosswinds.
With that umbrella left behind, those winds sheared Debby's clouds, sapping the power of thunderstorms, which in turn robbed the hurricane of its regenerative power. Franklin also has some insights into why the models failed to see all of that. But first, some background:
Hurricane models are computer programs that process an enormous array of atmospheric and oceanic conditions. From that, models predict a storm's path and intensity. Hurricane forecasters use a ``suite'' of models that is printed out every six hours. Sometimes, the models cluster in agreement. Sometimes, they vary widely. In either case, a meteorologist studies other computerized data, satellite photos and historical records, adds his or her own knowledge, experience and instinct -- and then issues a forecast.
``The science has gotten better, but it still requires an artist's hand,'' Lushine said.
Some models employed by the hurricane center are the same as those used around the world to produce routine weather forecasts. Among the most reliable models, according to hurricane forecasters:
At 5 p.m. Aug 22nd, those three models -- plus the 12 others -- aimed Debby generally toward South Florida. They ranged from just off Key West to Great Abaco Island off Palm Beach, but the concentration was relatively tight. Forecasters chose a path near the middle of the suite, practically right over the point selected by the Super Ensemble. The path pointed right at Pompano Beach.
The storm was still more than three days away, meaning that any such projection carried an average error of 250 miles, but the message was clear: South Florida was in the path of a hurricane.
``We couldn't ignore all of this guidance,'' Franklin said. ``It would have been irresponsible.''
But now we know that the models were wrong. Franklin said most models are designed to predict phenomena even larger than hurricanes -- cold fronts, for instance, and long, wide rivers of air called troughs -- and they obviously have problems dealing with the core of a hurricane, especially a core as poorly formed as Debby's.
Historically, Franklin said, models also overestimate the durability of upper level highs. This time, they also underestimated Debby's ability to race out from under that umbrella.
``We're seeing that things on this scale are too small for the models to pick up,'' Franklin said. ``We need models that represent what's going on in a hurricane's core, but the truth is, that's as good as the science and the art are right now.''