1 October 1998
Storm Brews Over Wind Speed Claims
Wind speeds in Hurricanes Bonnie, Earl and Georges were often overstated by the National Hurricane Center, according to a Clemson University researcher, who worries that bad science will lead to future disasters.
"People may not take proper precautions because they've been misled into thinking they've been through far worse storms than they actually have," said Clemson wind engineering professor Peter Sparks. "If winds in Hurricane Georges had blown as hard as stated by official sources, then the whole of the Gulf Coast would be torn apart like South Florida after Hurricane Andrew." Sparks has studied wind conditions in hurricanes for the past 15 years and has testified on wind-safety issues before a Congressional subcommittee. He is part of a research effort at Clemson that focuses on finding ways to strengthen homes and schools against the ravages of high-wind events such as hurricanes.
"Bonnie, Earl and Georges were three of the most heavily researched storms in history. Aircraft measurement, dropsondes and data buoys, as well as coastal and inland wind-recording sites, gave researchers a clear picture of what was going on - and the data simply didn't support the claims of the National Hurricane Center," Sparks said. In the most recent example of Hurricane Georges, the National Hurricane Center reported maximum sustained winds of 100 mph as it made landfall.
But Sparks said an analysis of information from data buoys and land stations by the Hurricane Research Division of the National Oceanic and Aeronautic Administration put the figure at only 84 mph for ocean exposures - which would mean overland speeds would be even lower.
The situation in Georges was complicated by some instrumentation problems, Sparks said. Valuable data from automatic weather stations in Gulfport and Pascagoula were lost because neither station had emergency-power capability, a common failing among the more than 900 automatic weather stations deployed by the National Weather Service, FAA and the military in recent years. Data from those stations would have helped to determine the validity of gusts of 175 mph reported at the nearby Keesler Airforce Base in Biloxi, which uses a type of wind-speed measuring device that's been proven to give erroneously high results when wet, Sparks said.
He added that erroneous reports also went out after Hurricane Bonnie, with the National Hurricane Center issuing reports that a Category -- hurricane with sustained winds of 115 mph had swept over Wilmington, N.C., even as the National Weather Service at Wilmington measured and reported a maximum of only 56 mph.
"The scientific information is there, but the National Hurricane Center is not using it properly. Even when we have good data - such as in Wilmington during Bonnie - nobody takes any notice of it. Despite great improvements in instrumentation, data transmission and significant improvements in track forecasts, the National Hurricane Center's reports of prevailing wind conditions have got worse, not better, over the years," Sparks said.
The problem has been long-standing, said Sparks. In 1985, he led a National Academy of Sciences team that investigated Hurricane Elena, which made landfall in almost exactly the same place as Georges. Having spent months recovering wind-data from the area, the team concluded that there was no justification for the wind speeds claimed by the National Hurricane Center.
"Government officials reported sustained winds of 100 mph and gusts of 175 mph for Georges, yet it's virtually impossible to find any wind damage. We got more accurate reports from the meteorological services in the tiny Caribbean islands than we got from the United States."
Wind speeds, as currently reported, are too easily open for misinterpretation by the public and press, Sparks said. For example, the National Hurricane Center uses the term "maximum sustained wind" to describe wind speed averaged over one minute at 33 feet above the surface - a quantity not measured directly by any meteorological station in the world and at odds with the World Meteorological Organization's sustained-wind standard that requires measuring wind over at least a 10-minute period.
Since gust speeds are widely reported by weather stations and often quoted by the media, it may make more sense for the National Hurricane Center, in its public advisories, to give wind speeds in terms of gusts instead of the more difficult-to-understand sustained wind speeds, Sparks said.