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Hurricane Gustav to Become Gulf Coast Monster?

Willie Drye
for National Geographic News
August 27, 2008
 
See more recent Hurricane Gustav coverage >>

The once and future Hurricane Gustav—currently a tropical storm over Haiti—could attack the U.S. Gulf Coast as a major hurricane this weekend. Or not.

The Gulf Coast's fate depends largely on a developing high-pressure system, whose southern edge extends roughly from the eastern Gulf of Mexico to the western Atlantic Ocean. (See a map of the region.)

High-pressure "ridges" repel storms, so if the developing ridge north of Cuba is strong, Gustav could be deflected westward and into the central Gulf of Mexico, where vast stretches of warm water could supercharge the storm as it heads for the U.S. coast.

But if the high-pressure system wanes, Gustav could turn north, unimpeded, and move overland, across Cuba. The temporary lack of contact with warm water would deprive it of power.

From Storm to Hurricane to Storm … to Hurricane?

Gustav began as a tropical depression in the eastern Caribbean Sea on Monday and quickly intensified into a Category 1 hurricane with winds of about 90 miles (145 kilometers) an hour.

Gustav hit shore Tuesday in Haiti and has been blamed for at least 17 deaths there and the neighboring Dominican Republic.

The passage over Haiti's mountains weakened Gustav's winds to about 60 miles (100 kilometers) an hour, reducing it to tropical storm status.

As of Wednesday morning, the center of Gustav was nearly stationary over Haiti. But the storm is expected to start moving westward later in the day. That would put it over the very warm waters of the Caribbean, and forecasters think Gustav will quickly regain its status as a Category 1 hurricane, with wind speeds between 74 and 95 miles an hour (119 and 153 kilometers an hour).

By early Saturday, Gustav is predicted to be just off the coast of western Cuba as a Category 3 hurricane, with winds between 110 and 130 miles (177 and 209 kilometers) an hour.

Where it goes from there—and how intense it becomes—is less certain.

(Related: "Hurricane Bertha's Burst of Strength Stumps Experts" [July 8, 2008].)

Path of Least Resistance

Gustav is expected to turn toward the U.S. sometime Friday or Saturday, and the high-pressure system will decide how sharp Gustav's turn will be.

"Once it starts moving, it will move west-northwest under the southern periphery of that ridge," said Rebecca Waddlington, a meteorologist at the National Hurricane Center in Miami.

"If the ridge gets stronger, that will keep Gustav moving farther west. If it gets weaker, the storm will move more to the north."

There is "no way of knowing" at present how the high-pressure ridge is going to evolve, Waddlington said. The present long-range forecast says Gustav could come ashore anywhere from the central Florida Panhandle to the Texas-Mexico border.

A hurricane will move along the edge of a high-pressure system until the storm finds a weak spot. Then the hurricane will move toward the weakness as though a door had suddenly opened.

Hurricanes "want to go to the weakest path they can find," said Gary Beeler, a meteorologist at the National Weather Service in Mobile, Alabama, said.

Plenty of Energy

To intensify, storms need water that is at least 80 degrees Fahrenheit (about 27 degrees Celsius). The warmer the water is, the more the hurricane can intensify.

Jeff Garmon, a National Weather Service meteorologist in Mobile, Alabama, said the water temperature in the Caribbean Sea and the Gulf of Mexico is currently as high as 89 degrees Fahrenheit (32 degrees Celsius) in some places.

"There's plenty of potential energy for Gustav to feed off of," Garmon said.

Even if a hurricane has warm water in front of it, however, upper-level winds known as wind shear can disrupt the storm's development and keep it from strengthening.

But wind shear will be very light over the Caribbean and Gulf for the immediate future, and will not impede Gustav's development, Garmon and Waddlington, of the National Hurricane Center, said.

Hard to Predict

There is always uncertainty about the path a hurricane will take, especially longer-term forecasts.

"It's a foregone conclusion that the forecast will have an error in the track," Garmon said. "That's what makes forecasting the intensity so hard." "I'd like to stress that we don't start getting really confident [about landfall location] until it's two or three days out," he said. "That's when you see the whites of its eyes."

"It's not time to panic just yet. But it's time to be aware of what's going on and have a plan in place."


Willie Drye is author of Storm of the Century: the Labor Day hurricane of 1935, published by National Geographic Books.

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