April 10, 2008
NCAR Radar Technique Adopted by Hurricane Center
The National Hurricane Center will implement a new technique this summer, developed by researchers at the National Center for Atmospheric Research (NCAR) and the Naval Research Laboratory (NRL), to continually monitor landfalling storms in the United States. The system, which relies on existing coastal Doppler radars, provides details on hurricane winds and central pressure every six minutes, indicating whether a hurricane is gathering strength in its final hours before reaching shore.
The technique, known as VORTRAC (Vortex Objective Radar Tracking and Circulation), was successfully tested by the National Hurricane Center last year.
"VORTRAC will enable hurricane specialists, for the first time, to continually monitor the trend in central pressure as a dangerous storm nears land," says NCAR scientist Wen-Chau Lee. "With the help of VORTRAC, vulnerable communities can be better informed of sudden changes in hurricane intensity."
Lee collaborated with NRL's Paul Harasti and NCAR's Michael Bell to develop VORTRAC. Funding came primarily from the National Science Foundation and the National Oceanic and Atmospheric Administration. The NHC is part of NOAA's National Weather Service.
One of VORTRAC's strengths is that it can use radar data to estimate the barometric pressure at the center of a hurricane, a key measure of its intensity.
"VORTRAC allows us to take the wind measurements from the radar, turn the crank, and have a central pressure drop out of a calculation," says Colin McAdie, a meteorologist at NHC. "This will be a valuable addition to the tools available to the forecaster."
Rapidly intensifying storms can catch vulnerable coastal areas by surprise. Last year, Hurricane Humberto struck near Port Arthur, Texas, after unexpectedly strengthening from a tropical depression to a hurricane in less than 19 hours. In 2004, Hurricane Charley's top winds increased from 110 to 145 miles per hour (about 175 to 235 kilometers per hour) in just six hours as the storm neared Florida's southwest coast.
Lee and his collaborators applied VORTRAC retroactively to the two hurricanes and found that the technique would have accurately tracked their quick bursts in intensity.
"VORTRAC has demonstrated that it can capture sudden intensity changes in potentially dangerous hurricanes in the critical time period when these storms are nearing land," Bell says.
Image2 Caption: Wen-Chau Lee. (Photo by Carlye Calvin, Ã©UCAR)
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