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Posted at 07:00 PM ET, 03/17/2008

Comment of the Week: Thunderstorm Winds

Each week, the Capital Weather Gang will search for an outstanding reader comment to potentially highlight on the blog. We found a good one this week. In response to Dan Stillman's "Weather 101: The Madness to March Winds", 'Mike' provided this insightful commentary :

...[T]here is another big factor in thunderstorms that produces strong winds.....not just a dry layer at 10,000-15,000 feet.

Thunderstorms usually reach their most severe intensities with what are called "tilted-updraft" storms. A normal, summer, air-mass thunderstorm occurs in a weak upper-level flow, thus allowing the storm's downdraft to gradually choke off the updraft flow of incoming warm, moist air, and the storm's intensity abates and dies.

This does not happen when winds aloft are strong....such in the vicinity of a jet stream. That is why one of the key ingredients forecasters look for in predicting severe thunderstorms is the presence, aloft, of cold air and strong winds....what is known as "wind shear". In a tilted-updraft storm, the downdraft does not fall back down on the updraft and choke it off....it is tilted by the jet stream winds at an angle, and descends with considerable force out ahead of the updraft. This can allow for storms of incredible violence....triple-digit wind gusts, large hailstones, and, if the wind direction varies with height, spinning and tornadoes.

Storms known as super-cells, that also produce tornadoes and extremely strong winds/hail, can also form from these conditions, but they are different, structurally, from tilted-updraft storms. Supercells are huge, individual storms that sweep in warm, moist air from all sides in a spinning motion. The entire storm becomes one large, spinning dynamo.

By  |  07:00 PM ET, 03/17/2008

Categories:  Thunderstorms

 
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