6/13/2012 - JOINT BASE SAN ANTONIO-RANDOLPH, Texas –
There have been 61 tornadoes in San Antonio since 1950, resulting in three deaths, Steve Clark, 902nd Civil Engineer Squadron readiness and emergency management chief, said. But compared to North Texas and states that make up "Tornado Alley," South Texas' tornadoes are nowhere close to those states' degree of costliness, frequency and deadliness.
This doesn't mean Bexar County residents shouldn't be equipped with what Clark called the best defense against tornadoes or any type of severe weather: "preparedness and awareness."
"The biggest mistake is when people don't take warnings seriously and react too late," he said. "Being informed and prepared can also be the hardest piece of advice to get across because it's really a personal choice."
Part of being prepared for tornadoes is practicing sheltering plans.
"Families must make sure everybody, including children, know the drills and take into account their pets too," Clark said.
All should seek shelter in a basement or in the center of a sturdy building during a twister.
"Closets or underneath a stairwell are good places to hide," Clark said, emphasizing that people should avoid sheltering near windows, but use blankets or mattresses to protect themselves from flying debris.
Clark recommended the purchase of a battery-operated AM/FM radio for severe weather updates, as well as a first aid kit for emergencies.
During a tornado strike, the best kind of vehicle safety is to not be in one.
Being inside a vehicle can be a fatal mistake, especially for drivers who don't know if they are heading away from or toward a tornado.
"You do not want to be in the path of a tornado while inside your car," Clark said. "Find the nearest cover or the lowest-lying area like a ditch and avoid seeking shelter under a bridge."
Bernoulli's principle states air moving through a constriction or over a curved surface will undergo a pressure drop and increase wind speed, potentially hurling debris at higher speeds.
Debris such as tree branches and poles that can be tossed at drivers - as well as trees falling on them - is the second-leading cause of death during Texas tornadoes, Clark said.
The only danger that has killed more people than debris strikes is downed power lines, which can be buried in rubble and electrocute people upon touch.
It is best for people to stay well away from downed power lines and not touch any objects near them, Clark said.
Most South Texas twisters are classified as F0s and F1s (with the strongest one in San Antonio being an F4 in 1953), which peak in April and May, and then peak again later in the year in October and November.
The dangers they present are strong winds and flying debris, which typically do not cause major structural damage to buildings, Clark said. However, the last tornado to touch down in the city Oct. 9 - classified as an EF1 on the Enhanced Fujita scale - was enough to tear the roof off a house, damage several other homes and "[toss] 19 postal trucks around like toys" near Joint Base San Antonio-Lackland, according to the San Antonio Express-News.
A National Weather Service representative said the Oct. 9 tornado produced winds that reached 90-100 miles per hour.
Airman 1st Class James Johnson, 359th Aerospace Medical Squadron medical technician, experienced a tornado with similar strength in July 2008.
An EF0 touched down on the southern edge of downtown near the Interstate 10-Interstate 37 interchange.
"I was in a shopping center near Fort Sam Houston when I got word that a tornado was about to strike," Johnson said, where he immediately sought shelter.
He described loud noises that came from the rattling winds as the tornado crossed through in close proximity.
Johnson didn't get to see the tornado, but said "the parking lot was pretty messed up with shopping carts thrown everywhere and the sign for a nearby Target was torn up."
His tornado experience prompted him to discuss and prepare sheltering plans with his family for future severe weather.
Alvin Hill, 12th Operations Support Squadron chief of weather flight operations, said relatively weak and short-lived tornadoes like EF0s are sometimes produced by tropical storms and hurricanes, but tend to be ignored because flash flooding presents a larger problem for the San Antonio region.
"High winds, torrential rainfall and inland flooding are primary components of tropical storms and hurricanes due to warm waters (in the Gulf of Mexico), but localized areas of a storm can produce tornadic activity," he said.
Hill noted that tornadoes most often occur in thunderstorms embedded in the rain bands well away from the center of a storm; depending on the size of the tropical storm, they can spawn 150-200 miles away from the center. However, tornadoes can generate near the "eyewall," generally in the right-front quadrant of the storm center.
The dangers tornados bring are only a piece of severe weather that may be forthcoming.
"We are in hurricane season, which runs until November 30," Hill said. "Tornado awareness should help us see the bigger picture in preparing for hurricanes."
Contact your building manager for information on weather safety plans. To reach the 902nd CES Emergency Management Flight, call 652-2222.