email a friend iconprinter friendly iconHurricanes
Page [ 4 ] of 8

Weather satellites make it easy for meteorologists to keep tabs on hurricanes. But ordinary satellite images show only the cloud tops. Space-borne infrared sensors can reveal more detail, charting the size and shape of the warm eye, and satellite radar and microwave sensors can map the rain. Hurricane hunter aircraft actually fly right into Atlantic hurricanes. But they only probe conditions at altitudes of several thousand feet, above the worst turbulence, Jack Beven of the NHC says—"not at the surface, where they really matter to people."

Last year, though, scientists flew a robotic aircraft straight into the maelstrom when tropical storm Ophelia was parked off the mid-Atlantic coast. The craft, called Aerosonde, swooped and circled for ten hours, as low as 1,200 feet (360 meters), monitoring winds and the flow of heat and moisture from the ocean into the storm.

That foray was a test, but forecasters routinely probe the heart of storms with shorter lived devices called dropsondes. Released from high-flying aircraft into hurricanes and the surrounding winds, these instrument-packed tubes descend by parachute. "They take about 15 minutes from 40,000 feet [12,000 meters] to splash," Majumdar says. Along the way, they measure temperature, pressure, humidity, and wind every half second, transmitting it all to the airplane before they hit the water.

By cranking dropsonde data into computer models that can simulate a storm and how it is likely to evolve, researchers have sharpened their forecasts of storm tracks. Three-day forecasts of Atlantic storm positions were off by an average of 440 miles (130 meters) in the 1970s; by 2005 the average error had dropped to 173 miles (280 kilometers). But one-day forecasts were still wide of the mark by an average of 70 miles (110 kilometers)—more than enough to keep coastal dwellers second-guessing the experts. The data and models still can't capture storms in enough detail to forecast all of their feints and swerves.

Storm intensity is proving even harder to forecast. Three-day wind-speed forecasts, off by an average of 23 miles an hour (37 kilometers an hour) in the early 1990s, had improved only marginally by 2005. Hurricanes regularly surprise observers with their mood shifts. In a matter of hours, a Category 5 storm (winds over 155 miles an hour [250 kilometers an hour]) can fade to a Category 3 (111-130 miles an hour [178-210 kilometers an hour]), or a mere tropical storm can explode into a killer. "Intensity changes are the things that really hurt people," says NOAA's Bell.

Page [ 4 ] of 8
- ADVERTISEMENT -