NOAA Magazine NOAA Home Page

NOAA SURVEYS MARYLAND STORM DAMAGE

April 30, 2002 — Hours after tornadoes sliced through Charles County, Md., Barbara Watson, warning coordination meteorologist at NOAA's National Weather Service Baltimore/Washington forecast office, found herself in a Maryland State Police helicopter, surveying storm damage from the air. On the ground her colleague Jim Travers, meteorologist-in-charge of the Baltimore/Washington office, was examining the remains of buildings, trees, and cars that were damaged or destroyed when a severe thunderstorm tore through the community. Other meteorologists fanned out into Virginia to examine reports of tornado damage there. (Click NOAA photo for larger view of home swept off its foundation in La Plata, Md., taken April 29, 2002. Click here for high resolution version of this photo. Note that this is a very large file. Please credit "NOAA.")

Travers and Watson constitute part of a local NOAA National Weather Service Damage Assessment Team, acting as meteorological detectives, looking for clues that will tell them the scope and magnitude of a tornado that struck the community of La Plata.

This investigation was repeated across the country Monday after a severe weather outbreak left more than 100 people injured, including numerous fatalities. Tornadoes touched down from the Midwest to the East Coast, the result of a vigorous storm system that tracked through the Midwest, drawing up warm and humid air from the Gulf of Mexico to collide with colder and drier air to the north. (Click NOAA photo for larger view of leveled home in La Plata, Md., taken April 29, 2002, after F5 tornado struck. Click here for high resolution version of this photo. Note that this is a very large file. Please credit "NOAA.")

Travers, speaking by cell phone while surveying the damage in Charles County, said the first task for a damage assessment team is to determine if a tornado did occur, or if damage resulted from straight-line winds that can reach speeds over 100 mph, but do not rotate like a tornado. Once the meteorologists have concluded that a tornado touched down, they look at what type of damage occurred to make an estimate of how strong it was on the Fujita Tornado Intensity Scale.

The Fujita or "F Scale" ranks tornadoes from F0 (weak tornado, winds to 72 mph) to F5 (extremely destructive tornado with winds from 261 to 318 mph). The ranking is determined by the damage inflicted by the tornado. For example, a weak tornado will knock over trees and cause some damage to the roofs of houses. A stronger tornado, an F3 for example, will cause damage to solidly constructed buildings. More violent tornadoes can scatter the bricks from buildings and level homes and businesses.

"It's like a detective, you look at all the clues that you have available, damage to structures, trees, etc. For example, in this La Plata tornado we have a 20- or 30-foot water tower that was blown over, this gives us insight into how strong the winds were," Travers said.

John Margraf, Information Technology Officer at the NWS Baltimore/Washington forecast office, said the information gathered by the teams helps victims get back on their feet after a disaster by providing detailed information to insurance adjusters about the meteorological phenomenon that occurred. The information is also used to train forecasters to continue to provide accurate and timely warnings in the future.

"We're going to take the information on their survey, compare it to data that we saved from our radar and computer models, and put all this together to use it as a case study," he said. "No matter how well forecast an event is, you can always do better. So we'll take this information and use it to improve our warning services in the future."

"This gives us a way to estimate in the future that when we have these kinds of Doppler radar tornado signatures and estimated radar winds, it produced a tornado of such a magnitude. It's kind of like ground truth, and while not the same as if we had an instrument to measure wind speed right there in the middle of the tornado, it is a pretty decent estimate," Travers said.

Margraf said the SKYWARN network, a national network of volunteer severe weather spotters trained by local National Weather Service forecast offices on how to spot severe weather, helped save lives by providing updated information on the location and track of the tornadoes and other dangerous conditions. "SKYWARN was very valuable on April 28. We were able to see indications of the tornadoes on radar, but nothing beats a confirmed report from a human," he said.

The Baltimore/Washington forecast office has about 2,000 active volunteers who cover 44 counties plus the city of Baltimore and the District of Columbia. When SKYWARN is activated by the forecast office, the volunteers, two-thirds of whom are licensed amateur radio operators, inform forecasters whenever certain criteria are met, including when one inch of rain has fallen, four inches of snow is on the ground or trees have been blown down. The reports are combined with radar and satellite data to help verify weather warnings and determine what the storms will do next.

Relevant Web Sites
NOAA's Storm Watch — Get the latest severe weather information across the USA

NOAA's Tornadoes Page

USA Weather Hazards

NOAA's Weather Page

NOAA's Storm Prediction Center

NOAA's National Severe Storms Laboratory

Media Contact:
Andrew Freedman, NOAA's National Weather Service, (301) 713-0622
(Photo courtesy of NOAA's National Weather Service Baltimore/Washington forecast office.)

 

-end-