STORM SIZE, INTENSITY, KEY TO EVALUATING POTENTIAL HURRICANE DAMAGE

May 11, 2007 � NOAA hurricane researchers investigating the destructive potential of land-falling hurricanes indicated that the overall size of the storm, as well as the area reached by its winds should be considered when assessing its possible damage. (Click NOAA image for larger view of the destruction from Hurricane Katrina in Biloxi, Miss. Click here for high resolution version. Please credit “NOAA.”)

The April issue of the Bulletin of the American Meteorological Society published a study by Mark Powell, a research meteorologist at the NOAA Atlantic Oceanographic and Meteorological Laboratory in Miami, describing what he calls a new Hurricane Destructive Potential classification. This metric associates a numerical value similar to the Saffir-Simpson scale to each storm, and reflects potential damage due to wind, storm surge and waves.

NOAA has not proposed modifying the current Saffir-Simpson hurricane scale.

Powell’s goal is to provide a better measure of the threat posed by a hurricane. He suggests revising classification of hurricanes to include other physical characteristics of the hurricane such as the overall size of the storm and the area affected by winds exceeding certain threshold values.

“By incorporating both size and intensity, I see this system as a better way to allow people to assess the true potential impact of an approaching storm,” Powell said. “If people knew that Katrina had a much higher damage potential than Camille, the Mississippi residents who chose to stay might have evacuated.”

Powell and his co-author, Timothy Reinhold, a scientist and engineer with the Institute for Business & Home Safety, acknowledge that people who decide to leave or stay in response to a hurricane warning make decisions based on perceived vulnerability. Past hurricane experience is one of several influences on this perception.

The authors propose that many coastal Mississippi residents may have decided to stay during Hurricane Katrina, a Category 5 hurricane 24 hours before landfall, because their location had not flooded during a previous Category 5 storm, Hurricane Camille in 1969. This decision was made despite skillful forecasts from the NOAA National Weather Service. While Hurricane Camille’s winds were stronger at landfall, Hurricane Katrina’s wind field was much larger, resulting in significantly greater coastal flooding and damage.

“The Saffir-Simpson scale has been a very valuable tool in warning people about hurricanes, but we have known for some time that the level of surge and surge-related damage is not well correlated with the maximum wind speeds at landfall,” said Reinhold. “The proposed methods may well lead to more consistent warnings of damage potential both for wind and surge. It could follow in the footsteps of NOAA’s recent adoption of the Enhanced Fujita Scale for classifying tornadoes and provide the foundation for an enhanced Saffir-Simpson Scale.”

To develop a scale that incorporates destructive potential due to storm surge and wind, Powell used kinetic energy calculations to classify small and large storms, ranging from Tropical Storm strength to Category 5 using data from NOAA’s H*Wind experimental product that effectively describes the variations in the size and shape of the wind field of a given storm. H*Wind is currently the best tool available to evaluate the extent of damaging winds based on all available observations.

Powell will test-run the Hurricane Destructive Potential classification during the 2007 hurricane season as part of NOAA’s H*Wind experimental products.

Hurricane season begins June 1 and ends November 30. NOAA will release its official outlook for the 2007 season on May 22.

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Relevant Web Sites
NOAA Surface Wind Analysis

NOAA Atlantic Oceanographic and Meteorological Laboratory

NOAA Hurricane Research Division

Media Contact:
Jana Goldman, NOAA Research, (301) 734-1123 or Erica Rule, NOAA Atlantic Oceanographic and Meteorological Lab, (305) 361-4541