Getting To The Heart Of Bonnie's Odd Behavior

By LEON JAROFF

While residents of North and South Carolina were retreating nervously before Bonnie's advance last week, NASA pilot Ken Broda was heading resolutely in the opposite direction. Guiding a converted U-2 spy plane to altitudes higher than hurricane-observation aircraft usually go, Broda was determined to get a look at what was happening at the storm's very crown.

What he saw was an utter surprise: perched at 55,000 ft. and a full 70 miles away from Bonnie's central eye sat a large domed cloud that Broda likened to a "mini-hurricane" swirling up from the top of the storm. In most hurricanes, wind is pulled up from the sea surface, through and out the top of the eye. But Bonnie was sucking in air at 35,000 ft. above sea level and exhaling it far away from its center. Says Ed Zipser, a Texas A&M hurricane expert who surveyed Bonnie from a NASA DC-8: "These storms are usually very symmetrical, but Bonnie was nothing like what we expected." Following that upper-level wind flow, Zipser's plane unexpectedly flew into what he calls a "spectacular" snowstorm.

Scientists have been studying hurricanes with every tool at their disposal for many decades now. But as Bonnie's bizarre behavior clearly demonstrated, they've barely begun to understand these great storms. That's why Broda and Zipser went up to confront Bonnie, why three other aircraft joined them and why two satellites peered down to transmit images of the storm to earth while ground-based radar probed deep into the swirling clouds. With enough data, researchers figure, it may finally be possible to predict the course and intensity of a hurricane with greater precision.

Not yet, though. At one point early last week, the atmospheric scientists fed Bonnie's vital statistics into a sophisticated computer model--one that already incorporated data from more than 70 other storms investigated over the past 20 years--and it told them the hurricane would never hit land.

Fortunately, experience told the scientists to be wary. In their uncertainty, forecasters issued warnings for a strip of coastline extending all the way from South Carolina to Virginia, a decision that had economic as well as psychological consequences. Experts estimate that for each mile of coastline within a warning zone, residents and localities fork out $1 million for plywood, generators and other emergency provisions. Yet, says Hugh Willoughby, director of NOAA's hurricane-research division, "it's a lot better to have a warning and no hurricane than to have a hurricane and no warning."

With the data gathered from Bonnie, scientists hope to improve their accuracy. Some of the best new information may well come from gadgets known as dropsondes. These are tiny automated weather stations, weighing less than 1 lb., that were parachuted from a DC-8 through seven miles of storm clouds. As they descended, the dropsondes recorded and transmitted their positions and the temperature, wind speed, pressure and humidity at each point. The unprecedentedly detailed information they gathered should help refine computer models, and thus the forecasters' predictions.

These and the other secrets coaxed from Bonnie should be digested in several months and ready to aid meteorologists in time for next year's hurricane season. Says Robbie Hood, NASA's lead scientist on the hurricane project: "I'm hopeful that with these flights we have gathered data that in the future will save lives." What nobody will predict, however, is that hurricanes have run out of surprises.

--By Leon Jaroff. Reported by Dick Thompson/Washington

With reporting by Dick Thompson/Washington