Friday, August 17, 2012

Hurricane forecasters seek to improve intensity predictions

Harvey Leifert in Environmental Research Web: Only three Category 5 hurricanes have hit the United States since record keeping began in 1851. Katrina was not one of them. For all its impact on the lives and economy of the Gulf Coast, Katrina was "only" Category 4 when it made landfall in 2005. The most recent Category 5 hurricane (winds over 252 km/h) was Andrew, which hit southern Florida and Louisiana 20 years ago this August. Scientists still consider it to be a benchmark.

Andrew caused an unprecedented $26 bn in damage in 1992, even though the storm struck south of the densely populated areas of Miami, Miami Beach, and Fort Lauderdale. To mark the anniversary and assess progress in hurricane prediction, the National Hurricane Center (NHC) in Miami assembled a panel of scientists who were active then and now.

It was clear that great progress has been made in tracking storms and predicting their onward paths. Max Mayfield, who worked at NHC when Andrew hit, and directed the centre at the time of Katrina, recalled that Andrew, the first named storm of 1992, formed on 14 August off the African coast. It became a hurricane on 22 August, just two days before hitting the Bahamas and south Florida.

Mayfield distinguished two types of hurricane forecast – track and intensity. Neither was particularly well developed in 1992. Over the past 20 years, he said, great progress has been made in predicting a hurricane's track. Television viewers are used to seeing a storm's projected path and its error bars. Still, he said, even now, the projected tracks are not as precise as he would like, and the models need to be improved.

As for intensity, "no one that I know of thought [Andrew] was going to be a Category 5 hurricane before it hit," Mayfield said. "We did not have very good models for guidance on intensity forecasting."

We still do not, acknowledged Richard Knabb, who was recently appointed director of NHC. Forecasters are typically off by one category of intensity, even a day before landfall, he said, adding that "rapid intensification continues to be a challenge", as it was with Andrew....

Hurricane Andrew on August 23, 1992

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