Researchers try to find out what makes hurricanes form

Published 5:06 pm Tuesday, August 15, 2006

Every hurricane season, clusters of showers and thunderstorms roll off the coast of Africa and head over the Atlantic toward America. Most of the 60 or so tropical waves never do any harm. However, about 10 eventually grow into tropical storms or monster hurricanes like Katrina and Andrew.

Researchers still don’t know exactly what makes some waves stay weak and others strengthen into hurricanes. So starting this week, NASA and the National Oceanic and Atmospheric Administration will study these tropical systems from their breeding ground in Africa west toward the U.S to try to find out.

Meteorologists know certain basics are needed for hurricanes to form: deep pools of warm water; warm, moist air; low air pressure. The puzzle is that those conditions and others are often in place for systems that don’t start spinning.

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“A lot of ingredients need to come together to make a hurricane develop,” said Jason Dunion, a Hurricane Research Division scientist who will lead NOAA’s efforts in the $4.5 million project. “We need to better understand how it ramps up and why does it weaken.”

While scientists have studied the area off Africa before, this will be the most in-depth research there, said Jeff Halverson, a NASA hurricane research scientist and a professor at the University of Maryland, Baltimore County.

The researchers hope their work will help forecasters make more accurate predictions of hurricane intensity. While errors in track forecasts have been cut in half over the past decade or so, predicting how strong or weak a hurricane can’t be done with much accuracy.

Intensity predictions are about 15 to 20 years behind the progress in track forecasts, Dunion said.

Some data gathered by the teams will be fed in real time to computer models, so forecasters could see improvements in intensity forecasts this year, he said. Other information will be analyzed over the long term.

Any research on the storms in their “seedling” stage is critical and should be helpful in improving forecasts, said Colorado State University hurricane researcher Philip J. Klotzbach, who isn’t involved in the study.

NASA is using a specially equipped plane based in the Cape Verde Islands 350 miles off Senegal to track and analyze the African easterly waves, which form over the eastern part of the continent and move west. Forecasters believe more than 80 percent of hurricanes of Category 3 or higher come from these waves.

“So many of the big storms that come off Africa are the ones that cause a lot of trouble in the U.S.,” Halverson said.

They also will examine the Saharan air layer, a large formation of hot, dry, dusty air that researchers say can stop hurricanes from developing. Computer models can’t make accurate hurricane forecasts using data on the Saharan air layer’s winds and moisture levels, so the team will work on improving that, Dunion said.

Once the systems head west into the central Atlantic, NOAA will take over and fly through them and the Saharan air layer to get data on how they interact.

Also used will be NASA satellites that can peer through storms to give a vertical cross-section, weather radar, balloons and computer models.

From the air and space, the team will gather an unprecedented amount of data on temperature, humidity, air pressure, rainfall, how dust particles affect clouds and other factors, Halverson said.

The monthlong project is called the NASA African Monsoon Multidisciplinary Analyses, part of a larger project to study West African monsoons.

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