SEVERE WEATHER Lecture 9 Definition of a Severe Thunderstorm The National Weather Service defines a severe thunderstorm as a thunderstorm that produces Hail of 1 inch diameter or larger And/or Wind gusts 58 mph or greater A tornado Note: this does not include lightning or heavy rain!
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Cyclones can advect warm, moist air from the Gulf of Mexico into the central plains
Other sources of moisture include the Pacific and Atlantic oceans
The change in the wind with height forces the downdraft to be separate from the updraft, which allows the storm to live longer and become severe
Roll cloud in Dodge County-not attached to parent thunderstorm cloud-associated with thunderstorm gust front. Sign of possible microburst activity
- Rising cloud motion often can be seen in the leading (outer) part of the shelf cloud, while the underside often appears turbulent, boiling, and wind-torn.
Stoughton, 8/2005 Tornado - Storm Chaser Scott A. Kampas
Do not typically form within 5° latitude of the equator due to the lack of sufficient Coriolis Force
Air converges in the center in a cyclonic pattern and diverges at the top. In the center of the storm, called the “eye”, the storm is mostly cloud-free
Made landfall August 29, 2005 as Cat. 3
August 28, 2005