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Severe Weather Awareness Week: Thunderstorm Dangers

The area is affected by numerous 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.

When conditions appear to be dangerous enough, the National Weather Service will issue a Severe Thunderstorm Watch. NOAA Meteorologist Chad Hahn explains the criteria for a watch.

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.

Once these conditions, along with lightning, and heavy rain become prevalent, the National Weather Service will issue a Severe Thunderstorm Warning.

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.

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.

As always, stay with KIOW or for the latest information if severe weather occurs.


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