Texas is affected by thousands of thunderstorms every single year and the public is reminded about the dangers of severe weather this week as part of National Severe Storm Preparedness Week.
The most dangerous thunderstorms are classified as severe and occur mainly in the spring and fall. Severe thunderstorms can produce damaging winds, large hail and tornadoes. A thunderstorm is defined as severe when it produces winds of at least 58 mph, hail 3/4 of an inch in diameter or larger, or a tornado.
Something important to remember about thunderstorm winds is that not all damaging thunderstorm winds are tornadic. Thunderstorms are capable of producing equally destructive and life-threatening thunderstorm winds commonly referred to as straight line winds. Straight line winds refer to winds that are not associated with rotating winds in a tornado, rather they move forward along the ground in unidirectional fashion. Lines of thunderstorms that develop across Texas can produce straight line wind speeds in excess of 100 mph.
Another type of straight line wind, the downburst, is a strong downdraft of air in a single thunderstorm that accelerates downward and produces an out-rush of damaging wind on or near the ground. Two types of downbursts exist: microbursts and macrobursts. The microburst is short-lived and of great concern to the aviation community. It produces strong winds in an area less than 2.5 miles in diameter. In contrast, macrobursts are longer-lived and capable of producing extensive wind damage across areas larger than 2.5 miles in diameter.
Straight line thunderstorm winds occasionally can reach speeds in excess of 100 mph. These types of winds are intense enough to uproot trees and produce substantial damage, if not complete destruction to buildings. If these winds occur in conjunction with large hail even more extreme damage can occur, such as causing holes in the sides and roofs of houses, or destroying crops and other vegetation.
Hail that is penny size (3/4 inch in diameter) or larger is considered severe. Hail is defined as precipitation in the form of lumps or chunks of ice that develop in some thunderstorms. Hail can range in size from pea size (1/4 inch) to greater than softball size (4.5 inches). Hailstones are usually oval shaped or round…but can be spiky in appearance. The largest hailstone on record in the United States fell at Aurora, Nebraska on June 22, 2003. The massive stone measured 18.75 inches in circumference and over 7 inches in diameter.
Hail falls to earth at speeds approaching 100 mph and as a result can produce immense damage to buildings, automobiles and vegetation. Annually, hail storms cause more than one billion dollars in damage across the entire United States. No part of Texas is immune to the dangers of large hail and although it is rarely fatal, it injures several dozens of people each year.
There are things you can do to help protect yourself and your property from the dangers associated with damaging thunderstorm winds and hail. Keep abreast of the latest weather conditions to avoid being caught in a severe storm. Monitoring weather radio from the National Weather Service as well as television, radio, and internet information will also help keep you informed of many of the approaching straight line wind or hail events in your area.
Treat straight line wind events the same as you would an approaching tornado. Seek shelter in a reinforced shelter, on the lowest floor, in an interior bathroom or closet, away from all windows. Always cover your head to protect against the impact of flying debris that can injure. If you encounter hail while driving, turn around. You may be driving into the core of a thunderstorm where tornadoes form. Report it to law enforcement as soon as it is safe to do so and seek an alternate route.
For more information and resources about weather safety, click here.
Pictured above is a thunderstorm, photo by NOAA.