A new eye on the storm

Hurricane Fabian, packing 135-mile-an-hour winds as it grazes the northern Leeward Islands and churns toward the Bahamas, is serving as a stark reminder that the 2003 Atlantic hurricane season has entered its peak period.

Now, federal and university forecasters say they could be poised for significant gains in their ability to give coastal residents, emergency planners, insurance companies, and others affected by tropical cyclones advanced seasonal and even monthly warnings of what an upcoming hurricane season is likely to hold.

The key, these scientists say, lies in what University of Maryland meteorology professor Eugenia Kalnay dubs the "genome project for the atmosphere"- a two-year effort undertaken in the late 1990s to take each day's raw weather data from 1948 to 1998 and run it through the latest weather-forecasting and analysis tools.

The results, researchers say, represent the most consistent picture yet of shifts in atmospheric conditions over a range of time periods. That consistency has allowed researchers to clearly spot global patterns that previous, smaller-scale studies had only hinted at and that could significantly improve seasonal forecasting of hurricanes.

The 50-year reanalysis comes from a joint effort of the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR). And it has yielded "extremely beautiful" data, says William Gray, a professor of atmospheric science at Colorado State University whose group has been issuing seasonal forecasts for 20 years. "We're going to see a lot of progress in seasonal prediction skill" as the reanalysis data are mined.

The reanalysis also appears to be paving the way toward shorter-term forecasts. Noting that tropical-cyclone activity can vary widely within a June 1 to Nov. 30 season, Dr. Gray's group has been devising methods to forecast such activity in the Atlantic during each of the peak months of August, September - and beginning this year - October.

For its part, the Climate Prediction Center (CPC) of the National Oceanic and Atmospheric Administration (NOAA) is a relative latecomer to the seasonal hurricane forecasting field. It began issuing its forecasts in 1998. While the CPC's methods and forecasts differ from Gray's in significant ways, CPC forecasters are gaining fresh insights from the NCEP/NCAR reanalysis on factors that can affect seasonal hurricane activity, notes Gerry Bell, lead forecaster for the agency's seasonal hurricane outlooks.

One of his group's major objectives, he says, has been to gain a better understanding of the atmospheric conditions that control the various time scales over which hurricane seasons become more or less intense than usual - especially time scales of multiple decades.

Indeed, researchers including Gray have noted that the Atlantic hurricane seasons appear to go through periods of several decades where seasonal activity is above or below normal. Since the mid-1990s, he notes, the Atlantic and Caribbean hurricane seasons appear to have moved into their stronger-than-normal phases.

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