National Weather Service changes severe-weather forecasting
New system geared specifically to assist public in pinpointing storm-based warnings
By LISA CARNLEY Staff Writer

When bad weather hits, Texas residents need to be prepared. One way to do that is to follow National Weather Service warning messages. Now those warnings will become even more area-specific with the new storm-based warnings program that went into effect Oct. 1.

Gary Woodall, warning coordination meteorologist for the National Weather Service Forecast Office in Fort Worth, said Lampasas can be a great example of how the program's changes will help localize weather events.

"This new process allows us to focus more specifically on the areas at risk and to not warn or alarm those areas that are not at risk," he said.

For example, he said, if a storm is centered between Lampasas and Kempner and moving east, NWS officials can keep Lometa out of the warning area. "A storm-based warning offers the potential to limit the area covered by warnings to those specific regions in which imminent threat exists."

The NWS began providing sub-county information in warnings in the late 1990s, said the weather official. A demonstration of the storm-basewarning system was conducted at 25 offices in 2005. "Even though Oct. marked the official start of storm-basewarnings, many offices have been practicing this policy for one or two years," said Woodall.

Storm-based warnings cover tornadoes, severe thunderstorms, floods and marine hazards. They provide more specific information about the location of severe weather and the direction it is expected to move. "This reduces the likelihood of needlessly alarming those outside the threat, which builds confidence in the warnings and increases the likelihood that people will take appropriate action," the Fort Worth forecaster said.

Weather officials believe storm-based warnings potentially will save more lives by focusing spotter and first-responder resources on the true area threatened by a given storm, and by allowing emergency managers to determine what warning sirens to sound.

"With the smaller warning areas, we will be able to more specifically state the areas at risk from a storm," Woodall said.

"Instead of stating that a warning is in effect for Lampasas County, we can state that the warning is in effect for southcentral and southeastern Lampasas County, for example. This should motivate people along U.S. Highway 190 from Lampasas to east of Kempner to take action."

By pinpointing the specific area of a storm instead of the entire county, the National Weather Service can reduce the area warned by as much as 70 percent.

Weather doesn't follow geographical boundaries, officials note, and stormbased warnings provide the public with more precise information for short-duration weather events.

In the past, an entire county could be placed under severeweather warnings, but under the new method, a polygon is drawn in the expected path of the storm to represent an area where the greatest threat for severe weather exists. The graphic version with polygons allows viewers to see the threatened area more clearly.

Television stations and Internet websites -- including the NWS website -- already have the capability to plot storm-based warning polygons. "The warning polygon data also will be helpful for emergency management officials," said Woodall.

Weather radio receivers will continue to function as before, he added. "However, once the warning alarm sounds, listeners can tune in to hear a more precise description of the warning area and a more detailed description of the storm's location, movement and potential impacts."

More information is available at www.weather.gov/ sbwarnings or at www.noaa.gov.