Following their December predictions for an active 2008 Atlantic basin hurricane season, several prominent forecasting teams have issued updated reports. Although the experts at Department of Atmospheric Science at Colorado State University (CSU), WSI Corporation, and Tropical Storm Risk (TSR) differ somewhat in their approaches and specific storm projections, they concur that the 2008 season will be above average. As Dr. Todd Crawford, seasonal forecaster at WSI, explains, this expectation stems primarily from the probable continuation of warmer-than-usual Atlantic Ocean temperatures.
“Since 1995, most tropical seasons have been more active than the long-term averages because of the warmer Atlantic Ocean temperatures,” Crawford said. “The current La Nina event, which is decaying somewhat this spring, should leave behind a wind shear environment that is favorable for the development of tropical systems in the summer and fall of 2008. We have increased our forecast slightly based on continued Atlantic warming in recent months, along with the persistence, albeit a bit weaker, of the La Nina event.”
The extended-range forecast released in April 2008 by CSU researchers Philip Klotzbach and William Gray anticipates the formation of 15 named storms, eight of which are expected to strengthen into hurricanes, and four are predicted to be “intense” hurricanes. Storms classified as “intense” typically reach Category-3 status or higher on the Saffir-Simpson scale and sustain low-level winds of at least 111 mph. The methodology of this year's CSU forecast is based on a recently developed statistical technique that draws on 58 years — spanning from 1950 to 2007 — of data.
In May, Hurricane Forecaster Joe Bastardi of AccuWeather.com presented an expanded forecast calling for increased risk of a destructive storm from the Carolinas to New England.
“Although we are forecasting a total of 12 named storms in 2008, much more important is the fact that a relatively high percentage of tropical storms are expected to make landfall and that the major threat area is farther north than normal,” he said. “We believe that at least 40 percent of named storms will cause tropical storms or hurricane conditions on the U.S. coastline, which is about 1.6 times the norm.”
So should the public heed these warnings, which some critics regard as little more than educated guesses? No strangers to the public scrutiny related to this arena, Klotzbach and Gray respond with an adamant “yes,” insisting that increased awareness is a measure of success. In the 25 years since the team began issuing seasonal hurricane forecasts, it has been subjected to numerous questions — as have its counterparts — about the accuracy of the report, or the perceived lack thereof.
Although the duo admits missing the mark at times, they offer no apologies. “We have not been ashamed of our forecast failures,” Klotzbach and Gray asserted. “It is the nature of seasonal forecasting to be wrong sometimes. The forecasts are based on statistical schemes, which, owing to their intrinsically probabilistic nature, will fail in some years.”
Mark Saunders and Adam Lea of Benfield University College London Hazard Research Centre, TSR, also adopted a straightforward approach in acknowledging discrepancies that have plagued its forecasts since 1988. “Users should note that the precision of our April outlooks for Atlantic hurricane activity for the past 20 years has been fairly low,” they said in a joint statement.
Readers should note that the feedback related to forecasting hasn't been entirely negative. For instance, WSI Corporation said its 2008 forecast follows a very successful 2007 track record. Even though its May 15 preseason values of 15 named storms, including eight hurricanes and four intense hurricanes, were slightly larger than the final observed values of 15, six, and two (respectively), the company seemed to fare better than other well-publicized tropical forecasters. WSI subsequently reduced projections in an August update to 14 named storms, including six hurricanes and three intense hurricanes, a correct prediction of a reduced risk of hurricanes relative to the May 2007 forecast.
Despite modeling deficiencies, new technologies and techniques continue to emerge. Just last month, WSI and Guy Carpenter introduced a forecasting tool called WSI LiveCat Forecast, which aims to improve upon the information provided by the National Hurricane Center. It works by employing meteorological models to accurately calculate twice a day the direction, intensity and duration of a named tropical storm or hurricane, along with the U.S. landfall probability as far as 10 days out. Only time will tell if it can deliver better results than previous forecasting tools have thus far been able to accomplish.
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