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...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, large hail and tornadoes. A thunderstorm is severe when it
produces winds of at least 58 mph, hail 1 inch in diameter or larger, 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 rotating winds
in a tornado. Rather, they move forward along the ground in unidirectional
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 longer 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. 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 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.
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 stronger thunderstorms. Hailstones are usually
oval shaped or round, but can be also be spiky in appearance. Hail can range in
size from pea size (1/4 inch) to greater than softball size (4.5 inches). 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
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.
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. 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.