New Tornado Scale

Reported May 2006

NORMAN, Okla. (Ivanhoe Broadcast News) -- Until now, the damage of an F5 tornado in Oklahoma was rated the same as if it struck Ohio. But now the National Weather Service is updating a standard tornado scale to reflect consistency in reporting storms.

On May 3, 1999, Mark Hay was watching a tornado at his office. As the twister tore through, Hay and eight of his co-workers ran for cover in a small closet of their dentist office.

"Figured this was gonna be the last day on earth for me," he says.

The storm Hay and his colleagues witnessed was an F5 on the Fujita scale, the scale used to measure tornadoes. All tornados that occur in the United States are given a number from 0 to 5 depending on the damage they do.

The old Fujita scale used to be based on what a tornado did to a well-built house, but building materials vary in different parts of the country. Now the National Weather Service is introducing an enhanced version of that scale. Meteorologists and wind engineers from all over the country came up with the new scale that rates tornado damage and estimates wind speed.

Joe Schaefer, Ph.D., director of the National Oceanic and Atmospheric Administration's Storm Prediction Center in Norman, Okla., says, "We have a slate of 28 different things we can look at the damage in ... It varies from where you are."

The Enhanced Fujita (EF) tornado damage scale takes into account things like damage to a sided house compared to a brick house or to a three-story building vs. a shopping mall. With the new scale, any wind speed over 200 mph is considered an F5 tornado whereas with the original scale, an F5 tornado had estimated wind speeds between 261 mph and 318 mph.

Schaefer says the EF will make reporting of tornadoes more consistent. And because wind speeds for each F level are lower, home builders can increase safety factors, making it safer for all of us. He hopes builders will see that and start building houses to meet the standards, giving more people like Hay a chance to survive a devastating tornado.

Meteorologists expect the EF scale to be fully implemented by February 2007.

Click here to Go Inside This Science or contact:

Joe Schaffer, Ph.D.
NOAA/National Weather Service
National Centers for Environmental Prediction
Storm Prediction Center
1313 Halley Circle
Norman, OK 73069
spc.feedback@noaa.gov
http://www.spc.noaa.gov/efscale

For more information on weather phenomena and meteorology:

The American Meteorological Society
45 Beacon Street
Boston, MA 02108-3693
(617) 227-2425
http://www.ametsoc.org

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