Severe Weather Awareness Week--Severe Thunderstorms

Make a Plan

Severe Thunderstorms

Flash Flooding

Tornadoes

Lightning

Watches, Warnings, & Reception

Mobile Home Safety

Severe Thunderstorms, Damaging Winds, & Hail

Damaging Winds and Hail

Louisiana, Texas, Arkansas, and Oklahoma are affected by thousands of thunderstorms every year. The strongest and most dangerous of these thunderstorms are defined as severe thunderstorms. Severe thunderstorms are thunderstorms which produce damaging winds of at least 58 mph, large hail at least 1 inch in diameter, or a tornado. Severe thunderstorms can occur during any time of the year in our Four State Region, but are most common during the spring and autumn months.

Thunderstorms are capable of producing very strong winds, but it is important to remember that not all damaging thunderstorm winds are caused by a tornado. Straight-line winds refer to winds that are not associated with the rotating winds in a tornado. Rather, they move forward along the ground in unidirectional fashion.

One form of straight-line winds, the downburst, is a strong downdraft of air that accelerates toward the ground in a thunderstorm. Once near the ground, the downdraft can no long descend and therefore radiates outward in all directions, producing a sudden rush of damaging winds at the surface. Two types of downbursts exist: the microburst and the macroburst. The microburst is a short-lived event and of great concern to the aviation community. Microbursts produce 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 several miles in diameter.

Straight-line thunderstorm winds occasionally reach speeds in excess of 100 mph. These winds may be intense enough to uproot trees and produce substantial damage, if not complete destruction, to buildings. If these winds occur in conjunction with large hail, the damage will likely be even more extensive.

Did You Know?

Downbursts and microbursts can produce winds as high as 150 mph. That's equivalent to a Category 5 hurricane or an EF-3 tornado!

Treat straight-line wind events the same as you would an approaching tornado. Seek shelter in a reinforced building, preferably on the lowest floor, in an interior room or closet and away from any windows. Always cover your head to protect against the impact of flying debris.

Hail that is 1 inch in diameter (as big around as a quarter) or larger is considered severe. Hail is defined as precipitation in the form of lumps or chunks of ice that develop inside strong thunderstorms. Hailstones are usually oval-shaped or round, but can also be spike in appearance. Hail can range in size from pea size (one-quarter of an inch) to greater than softball size (4.5 inches).

Did You Know?

The largest diameter hailstone officially measured fell in Vivian, South Dakota, on July 23, 2010. This hail stone measured 7.9 inches in diameter, had a circumference of 18.622 inches, and weighed 1.9 pounds!

Hail Records

Largest Diameter	7.9 inches--Vivian, SD (July 23, 2010)
Heaviest Weight	1.9375 pounds--Vivian, SD (July 23, 2010)
Largest Circumference	18.75 inches--Aurora, NE (June 22, 2003)

The largest hailstone on record in the United States fell at Aurora, Nebraska on June 22, 2003. This massive stone measured 18.75 inches in circumference and over 7 inches in diameter.

Hail falls to earth at speeds approaching 100 mph and can cause 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 the Four- State region is immune to the dangers of large hail. Although being struck by hail is rarely fatal, several dozen people are seriously injured each year in hailstorms.

If you encounter hail while driving, turn around. You may be driving into the core of a thunderstorm, which is where tornadoes form. Report hail or wind damage to law enforcement as soon as it is safe to do so and seek an alternate route.

To protect yourself and your property from damaging winds and hail associated with a thunderstorm, it is important to stay abreast of the latest weather conditions. Staying updated through NOAA Weather Radio from the National Weather Service, as well as monitoring television, radio and the internet, will help you be better prepared for the dangers associated with any severe thunderstorms in your area.

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