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Definition of Storms by “Category” Is Questioned

Residents of Louisiana’s Plaquemines Parish and other coastal areas of the Gulf Coast may not have been fully prepared for the flooding caused by Hurricane Isaac because of its classification as a Category 1 hurricane
September 4, 2012

Residents of Louisiana’s Plaquemines Parish and other coastal areas of the Gulf Coast may not have been fully prepared for the flooding caused by Hurricane Isaac because of its classification as a Category 1 hurricane. Many meteorologists use the Saffir-Simpson scale, which ranks storms by categories, with Category 1 being the weakest. Experts have long criticized the scale, contending that it is misleading because it is primarily based on the power of the wind and fails to take account of the surge of water being pushed by the storm.

Kerry Emanuel of the Massachusetts Institute of Technology and other climatologists have called for a classification system that includes both wind speed and surge to prevent coastal residents from being misled. Hurricane Ike, which made landfall in Galveston, Texas, as a Category 2 storm is an example of a hurricane that ranked low on the Saffir-Simpson scale but was devastating. On August 30, Maxwell Agnew, an Army Corps of Engineers staff hydrologist, said that the surge from Isaac was not significantly smaller than the one from Hurricane Katrina, the Category 3 storm that overwhelmed New Orleans’ inadequate flood walls and levees. The surge from Katrina in Lake Borgne, east of the city, was 15.5 feet, only a little higher than the 14 foot wall of water pushed by Isaac in the same location. The National Oceanic and Atmospheric Administration said that there is no simple alternative to the Saffir-Simpson scale, since surges vary according to coastal conditions.

Definition of Storms by “Category” Is Questioned (New York Times 8/30/2012)

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