As Florida braces for the possible impact of a third major hurricane, weather experts say it’s true what we’re thinking: This is not your average hurricane season.
The eight named storms in August, starting with Hurricane Alex and ending with Tropical Storm Hermine, broke the record of seven for the month and are twice the average, according to the National Hurricane Center. The area covered includes the Atlantic Ocean, Gulf of Mexico and Caribbean Sea.
This month brought Hurricane Ivan, which forecasters say may hit the Florida Keys as soon as Monday. It all adds up to “a very active year,” said William Gray, a professor of atmospheric science at Colorado State University.
The storms also stand out for their intensity. Already, four hurricanes have been ranked at Category 3 or above, with winds of more than 111 m.p.h.–strong enough to knock down large trees and damage homes.
“We are in a period of more strong storms,” said storm expert James Elsner, a geography professor at Florida State University.
That wouldn’t matter so much if those storms fizzled out at sea. But this season, many are hitting land.
Florida, still recovering from damage caused by Hurricanes Charley and Frances, hasn’t seen anything like this in nearly four decades. Between 1966 and 2003, Florida was hit with only two major hurricanes: Hurricane Andrew in 1992 and Hurricane Opal in 1995. Between 1926 and 1965, there were 14.
Hurricanes are severe tropical disturbances with thunderstorms that form in the southern Atlantic Ocean, Caribbean Sea, Gulf of Mexico and in the eastern Pacific Ocean at certain times of the year. Many of the intense storms this season were triggered in Africa, Elsner said.
Key ingredients in hurricane formation include a distance of at least 300 miles from the equator, ocean temperatures of at least 80 degrees to a depth of 164 feet and heavy moisture in the lower and middle part of the atmosphere.
Warm ocean water fuels hurricanes, which produce winds of at least 74 m.p.h. and rotate counter-clockwise around a central core or “eye.”
Hurricanes are classified by wind speed using the Safir-Simpson hurricane scale. Winds in a Category 4 hurricane such as Ivan exceed 130 m.p.h. The most severe, Category 5, produce winds more than 155 m.p.h.
Wind and heavy waves called storm surges–which sometimes reach heights of 18 feet along the coast from a hurricane landfall–are what make the storms so destructive.
Hurricane season normally begins in June and is officially over by Nov. 30, according to the National Weather Service. This season there have been five hurricanes: Alex, Charley, Danielle, Frances and Ivan.
The word hurricane comes from the ancient Taino tribe of Central America, who called their god of evil Huracan. The term was adapted by Spanish colonists, whose diseases destroyed the Taino people.
Only in the last hundred years have scientists have been able to study hurricanes in depth. Researchers can spot them when they form, create computer models, fly through them and use techniques such as infrared satellite and water vapor imagery to examine their makeup and predict their behavior.
But they still cannot say with any authority what a hurricane will do. Hurricane Ivan, for instance, may hit Florida or head into the Gulf of Mexico.
Elsner said two theories have been advanced to explain the Atlantic hurricanes’ increasing power.
One is that changes in what is known as the “North Atlantic oscillation”–sea levels that seesaw between Iceland and the Azores–combined with a high-pressure zone near Bermuda have kept storms rolling west, picking up power over warm tropical seas instead of veering into colder latitudes. Changes in the oscillation take place every 20 to 30 years, Elsner said.
Another theory is that surface sea temperatures are rising.
“There are patterns of sea surface temperatures that were cooler in that period and now are warmer again,” Elsner said.
A lot remains uncertain, he added. But he and other experts doubt that global climate change is a factor.
“This is natural stuff. This is not human-induced global warming,” Gray said.
Hurricane activity for the first half of the 20th Century was stronger than in the second half, and some researchers say we now may be entering another active cycle.
“The Florida landfall of Major Hurricanes Charley and Frances, although very unfortunate, should not be taken as indicating that Florida is experiencing anything different than what it has seen in the past,” Gray wrote in a recent paper. “The real surprise should be that Florida … has experienced so few major hurricanes since 1965 as compared with earlier periods.”
The last time three hurricanes made landfall on Florida was 1964, when Cleo, Dora and Isbell raged across the state.
Such a triple whammy has a 2 percent chance of occurring in the U.S. each year, according to a firm that creates computerized models of extreme risk for the insurance industry.
“There have been cases of three landfalls affecting Florida, but they’re rare,” said Bob Healy, a senior executive with EQECAT Inc. “Based on the strength of the storms, as well as their number, we would expect it only to happen twice a century.”
The most hurricanes ever–12–occurred in 1969.
As for why some hurricanes meander on shore and others don’t, Gray said: “That is sort of random.”
“It could have been that these storms missed Florida and nobody would be worked up about them,” he said.
