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Hurricane Forecasters Wrestle With Uncertainty to Track Tricky Storms

BY Admin  September 12, 2008 at 5:25 PM EST

Ike over the Gulf of Mexico; NOAA

But earlier in the week Ike’s intended route wasn’t so clear. Variations in weather patterns make it tricky to predict a storm’s path with precision, and Ike was first expected to hit South Florida. Then, as the hurricane winds shifted, attention turned to Texas and the south Louisiana coast.

All week, meteorologists have been pulling from their arsenal of technologies to track the storm’s movement and intensity in order to alert those in danger.

Meteorologists use satellite imagery to determine the general size and location of an approaching hurricane. The U.S. Air Force and the National Oceanic and Atmospheric Administration also fly powerful aircraft through and around storms to locate the eye with more precision and to better understand the upper atmospheric wind currents that help to steer the hurricanes.

Three or four days before landfall, these planes drop instruments called GPS dropsondes from the air into the storm. The so-called sondes measure temperature, humidity, pressure and wind currents in and around the storm.

“You’re gathering data over a large area and putting that into complex computer weather models,” said Mark DeMaria, a research meteorologist and hurricane expert with NOAA. “You run models to produce forecasts of the eventual path of the storm.”

Forecasters usually begin to put real stock in the forecasts when different computer models begin producing similar tracks.

Judging the path of a hurricane is complicated, but determining whether a storm will grow or weaken before making landfall is even more difficult.

Wind and ocean surface temperatures factor into a storm’s strength, but “predicting how strong it’s going to be is probably one of the most uncertain factors of the forecast,” DeMaria said.

Lynn “Nick” Shay, professor of meteorology and physical oceanography at the University of Miami, attributes the uncertainty to a lack of reliable computer models designed specifically to predict storm intensity. Significant inroads could be made with stronger models, he said.

“The issue here is getting ocean atmosphere models built and tested,” he said. “To get these tested, you need to have data. And a model is only as good as its data.”

As for Ike, it has so far taken a typical journey for a Northern hemispheric storm, forming between Africa and the Caribbean Islands, tracking west across the Atlantic Ocean and curving toward the Gulf of Mexico and the eastern coast of the United States.

Storms often follow this path along what’s known as the “Loop Current,” which flows clockwise through a channel between the Yucatan Peninsula and Western Cuba, loops around and exits out the Gulf of Mexico and into the Florida Straits.

The Loop Current brings warm water with it, and as hurricanes move along this path, they often increase in intensity.

“When storms encounter warm ribbons of heat, they intensify and get stronger,” said Shay.

Unlike the deep waters off the Florida coast, water along the Gulf of Mexico is shallow, which makes the Gulf Coast region susceptible to dangerously high storm surges.