With Tropical Storm Guillermo headed toward Hawaii (potentially) in the eastern Pacific and the Atlantic showing the first signs of hurricane-spawning life, the 2009 hurricane season is gearing up.
But what is captivating the public's attention today are two hurricane studies with conclusions that seem to be at odds, continuing the long scientific debate about global warming and other longterm influences on hurricane activity.
The first and most written about study concludes that the Atlantic Ocean is producing more frequent and intense hurricanes than at any time in the past 1,000 years. The study was conducted by the director of the Earth System Science Center at Pennsylvania State University, Michael Mann, a prominent hurricane researcher, and colleagues there and at Woods Hole Oceanographic Institution. Hurricane activity 1,000 years ago may have exceeded the levels seen today, but it's been a long long time since humanity dealt with this level of hurricane activity.
The study, which relied on analysis of ocean sediments, seemed to reinforce the view that there are two primary factors that fuel hurricane activity: The cyclic El Nino-La Nino phases in the southern Pacific Ocean (El Nino, a warming pattern, which we're experiencing now, tamps down hurricane activity, while La Nina boosts it) ... and surface ocean temperature. That final factor is at the center of the debate over global warming's effect on hurricane activity, since global warming may increase the surface temperature of ocean water in parts of the Atlantic.
The second study, however, calls into question the apparent increase in recent (past 100-125 years) hurricane activity. In essence: There appear to be more storms because we're able to detect more short-lived tropical storms than we could before we developed satellite technology and other advanced tracking techniques, according to the National Oceanographic and Atmospheric Administration study published in the Journal of Climate.
The Atlantic has yet to see a named storm, and only the second tropical depression of the season is currently active. In the eastern Pacific, seven named storms have been documented: Tropical Storm Andres, which formed June 21 and reached hurricane strength for a few hours on June 23 without doing any damage; Tropical Storm Blanca formed July 6 and dissipated by July 8; Hurricane Carlos flared up twice from tropical storm to hurricane strength between July 10 and July 16; and Tropical Storm Dolores, which briefly flared up July 15 and July 16; Tropical Storm Enrique, which formed Aug. 3 and Hurricane Felicia, which formed Aug. 4; and Tropical Storm Guillermo which formed Aug. 13 and remains active.
Last year, the Atlantic saw 16 named tropical storms -- from Arthur on May 30, which killed five and caused $78 million in damages to Belize, to Hurricane Paloma, which formed Nov. 5 and struck Cuba as a Category 4 monster that was the second-most intense hurricane ever recorded in November. All in all, there were eight Atlantic hurricanes and storms caused an estimated $41 billion in damages and left hundreds dead -- more than 800 in Haiti alone.
The eastern Pacific also saw 16 named storms, seven of them hurricanes, starting with Tropical Storm Alma on May 29 and ending Nov. 5 when Tropical Storm Polo petered out.
The 2008 hurricane season produced several record-breaking storms, including Tropical Storm Alma; the easternmost named storm ever to form in the Pacific and Hurricane Bertha, the longest-lived Atlantic tropical storm on record. Four storms were notable -- or deadly -- enough that the names were retired -- Alma, Gustav, Ike and Paloma. Hurricane Gustav caused $4 billion damage in Louisiana and killed 112 people, including 77 in Haiti. Hurricane Ike was the season's strongest hurricane, and the third-costliest storm (more than $19 billion) to hit the U.S., devastating Galveston, Texas, and causing about 100 deaths in the Caribbean and along the U.S. Gulf Coast.
What's in store for 2009?
Whether and how global warming will influence hurricane frequency or intensity is still a matter of genuine scientific debate. In recent years, scientists have at least identified several factors -- from the extent of rainfall in Africa to the presence or absence of El Nino conditions in the Pacific -- that help them predict the intensity of a hurricane season ahead of time. Scientists recently announced the formation of a new El Nino pattern in the eastern Pacific, which tends to reduce the number and intensity of Atlantic hurricanes.
Here's how the two most prominent forecasters revised their forecasts in early August:
The federal government in May had predicted a "near normal" hurricane season for the Atlantic, with a 25% chance of above-normal outbreaks and 25% chance of below-normal outbreaks. Now, it predicts a 50% probability of a near-normal season, a 40% probability of a below-normal season, and just a 10% probability of an above-normal season.
The National Oceanographic and Atmospheric Administration predicts a 70% chance of:
The other major forecaster in the U.S., Colorado State University, revised down its expectations for the 2009 Atlantic hurricane season once already, and did it again in August:
Further, the Colorado forecasters predicted that the probability of a hurricane striking the U.S. coastline is 46% (down from 54%).
Forecasters warn that the number of storms, and their intensity is only one key determinant of risk of property damage and loss of life: The biggest factor is who lives in harm's way, and how well they prepare. Some 35 million U.S. residents live in hurricane-prone regions, and experts urge them to prepare.
When those storms do come, they will be given names. Tropical cyclones are given names when they achieve tropical storm strength, with sustained winds of at least 39 mph. Hurricanes are tropical storms that have sustained winds that exceed 74 mph, and major hurricanes have sustained winds that exceed 111 mph.Here are the tropical storm and hurricane names for 2009:
Names refer to the highest strength the storm reached, while dates refer to the dates during which the storm retained at least tropical storm strength.
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