Bituminous Insurance Companies
Release Date: May 25, 2010
The National Weather Service (NWS) has announced that it will be using a new hurricane wind scale for the 2010 tropical cyclone season. The new scale, the Saffir-Simpson Hurricane Wind Scale (SSHWS), replaces the Saffir-Simpson Hurricane Scale (SSHS) which has been used since 1975 to convey the threats of hurricanes.
The new scale keeps the same 1 to 5 rating scale and wind speed ranges as the original scale, but will no longer tie specific storm surge and flooding effects to each category. Storm surge ranges and flooding predictions were eliminated because they depend on factors other than wind speed and were frequently outside the ranges suggested in the original scale. For example, Hurricane Ike (2008) made landfall in Texas as a Category 2 hurricane based on wind speed, but had the peak storm surge estimated for a Category 4 storm. In contrast, Hurricane Charlie (2004) struck Florida as a Category 4 hurricane and produced a storm surge predicted for only a Category 2 storm.
Focusing the new scale solely on peak winds is intended to reduce public confusion over the impacts associated with the various hurricane categories and to improve emergency preparedness decision-making. Storm surge forecasts will continue to be included separately in hurricane advisories and statements issued by the NWS and National Hurricane Center (NHC).
The new wind scale also updated the wind-caused damage descriptions of the prior standard. These descriptions include a summary statement for each category, e.g., the summary statement for a Category 1 Hurricane is "Very dangerous winds will produce some damage," and more specific statements concerning wind impacts on the effect of the wind on people, livestock, and pets; several categories of building construction and building elements; trees; and water and power. Expected damage to high-rise windows and glass are now specifically addressed, as is damage to signage, fences, and canopies.
NHC cautions that these statements provide general descriptions of impact and that hurricane wind damage is very dependent on factors other than wind speed, such as the age of building stock and the construction practices used. One group of respected wind scientists had suggested developing separate damage statements for Florida and the Carolinas, since these states have more stringent building codes than other states.
The Saffir Simpson Hurricane Wind Scale was used by the NWS on an experimental basis during the 2009 hurricane season. They also solicited public comments for changes throughout 2009. Detailed information on the new scale is available from the NWS website at http://www.nhc.noaa.gov/aboutsshws.shtml.
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The information contained in this publication was obtained from sources believed to be reliable. ISO Services Properties, Inc., its companies and employees make no guarantee of results and assume no liability in connection with either the information herein contained or the safety suggestions herein made. Moreover, it cannot be assumed that every acceptable safety procedure is contained herein or that abnormal or unusual circumstances may not warrant or require further or additional procedure.