North Carolina State University News Services
Campus Box 7504
Raleigh, NC 27695
(919) 515-3470
Media Contacts:
Dr. Steven Koch, 919/515-1439 or [email protected]
Dr. Steve Harned, NWS, 919/515-8209, ext. 222, or [email protected]
Tim Lucas, News Services, 919/515-3470 or [email protected]
April 27, 1998
Research Yields Improved Tools for Forecasting Tornadoes
FOR IMMEDIATE RELEASE
RALEIGH, N.C. -- Advance warning can spell the difference between life and death for persons living in a tornado's path. But forecasters in the Southeast have long worked at a disadvantage. Their forecast tools and training are based largely on tornado research in the Midwest, where the super-cell storms that spawn most twisters are different than tornadic storms here.
Meteorologists at North Carolina State University and the National Weather Service at Raleigh are identifying those differences and developing new tools and training programs geared specifically to forecasting Southeastern tornadoes.
"We've already found several differences in the regions' storms' radar signatures -- features that forecasters here need to look for, but have previously never been trained to," says Dr. Steven Koch, associate professor of meteorology at NC State.
One of the most significant features, documented by NC State graduate student Christopher Vandersip of Durham under Koch's supervision, is that super-cell mesocyclones that spawn tornadoes in the Southeast are 40 percent to 50 percent shallower than those in the Great Plains.
That's important, Koch says, because it affects the algorithms used by Weather Service computers to alert forecasters when tornado warnings should be issued. Because of the curvature of the earth, radar images of weather 100 miles away from the radar site show what's happening up around 10,000 feet, he explains. At that altitude, a shallow mesocyclone near the earth's surface might slip by unnoticed until it moves closer or is reported by spotters on the ground. "That reduces the amount of advance warning you can give," Koch says.
A super-cell storm is a severe thunderstorm capable of producing damaging hail, destructive winds and heavy rain. A mesocyclone is the circulation within the super cell that produces most tornadoes. Ninety percent of mesocyclones produce severe weather; about one third spawn twisters.
Steve Harned, meteorologist-in-charge of the National Weather Service (NWS) Raleigh forecast office located on NC State's Centennial Campus, says Weather Service offices across the Southeast are primed to incorporate the severe storm research from the NWS' collaboration with the university.
"We are taking full advantage of our opportunities to transfer research discoveries directly to the forecast desk, so we can give residents advanced notice of severe weather so they have more time to protect lives and property," he says.
Earlier NC State-NWS forecast models on Southeast tornadic thunderstorms and on Southeast winter precipitation already have been incorporated into Weather Service operations regionwide. "We've been showing results from this collaboration since 1994," says Harned. "Now, we're building on our success."
Other new technologies produced through the partnership that may soon be implemented regionwide are high-resolution forecast models and temperature fields that are retrievable from Doppler radar. Using these tools, forecasters should be able to detect the presence of cold fronts aloft, Koch says. Cold fronts aloft are unsettled weather phenonena that move at higher altitudes hundreds of miles ahead of surface cold fronts, and can trigger lines of tornadoes and severe thunderstorms.
"Both of the tornado outbreaks in North Carolina this year were, by all indications, produced by cold fronts aloft," says Koch. "Yet, most forecasters are not trained to understand or spot them. They don't know where to look or what to look for."
The new technologies locate the otherwise hidden fronts by deriving atmospheric temperature fields from wind profiles supplied to forecasters via Doppler radar images every six minutes. In August, Koch will train NWS forecasters from across the Southeast how to use the new technology.
"We've come a long way toward understanding the unique characteristics of tornadoes and severe thunderstorms in the Southeast, but there's a lot we still don't understand," he says. "Why do some mesocyclones produce tornadoes and others don't? And why are some smaller tornadoes here produced by phenomena other than mesocyclones? The more answers we have, the more accurate our severe weather forecasts will be."
Funding for the collaborative research and training program comes from the Cooperative Program for Operational Meteorological Education and Training (COMET), in the form of a sub-award under a cooperative agreement between the National Oceanic and Atmospheric Administration and the University Corporation for Atmospheric Research.
-- lucas --
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