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Thunderstorms & Tornadoes. Question of the Day. Where would you expect to find the greatest proportion of Tstorms and why?. Cyclone. Circulation around ANY low-pressure center Intensity and size do not matter Tornadoes and Hurricanes are smaller than mid-latitude cyclones and more violent.
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Question of the Day • Where would you expect to find the greatest proportion of Tstorms and why?
Cyclone • Circulation around ANY low-pressure center • Intensity and size do not matter • Tornadoes and Hurricanes are smaller than mid-latitude cyclones and more violent
Thunderstorms • Storm that produces lightning and thunder • Characterized based upon the up/down draft of air NOT circular motion of air • Forms when warm, humid air rises in an unstable environment • Unequal heating of earth’s surface (Air-Mass Tstorms) • Unequal heating along with frontal wedging or oorgraphic lift (Severe Tstorms)
Air-Mass Thunderstorms • Occur in mT air that moves Northward from Gulf. • Most frequent during Spring and Summer • Frequently around midafternoon • Thunderstorm Project produced a model of the life cycle of a Tstorm • Cumuls Stage • Mature Stage • Dissipating Stage
Cumulus Stage • Formation of cumulus clouds allow for moisture to be at greater heights • Clouds grow vertically • Cumulonimbus clouds form • Dominated by updraft • Downdraft forms and failing precipitation causes drag • Entrainment intensifies downdraft
Mature Stage • Officially starts when precipitation leaves the cloud • Updraft and downdraft exists side by side and grow the cloud • Anvil top forms when cloud reaches base of the stratosphere • Most active stage: Gusty winds, ligthning, hail/heavy precipitation
Dissipating Stage • Dominated by the downdraft • Cooler air aloft and falling precipitation causes cloud to evaporate
Severe Thunderstorms • Characterized by heavy downpours, flash flooding, strong/gusty winds, hail, lightning, and maybe tornadoes. • Must have winds over 58mph or hailstones .75 in diameter or produce a tornado
SupercellTstorms • Single, powerful cell up to 65,000’ and 12-30 miles in diameter • 2000-3000/year in the US • Can form mesocyclones when updraft rotates
Thunder & Lightning • Thunder is: Expanding air • Heat Lightning • Lightning is created due to separation of charges in a cumulonimbus cloud • Sheet Lightning • Within the cloud or between clouds • 80% of all lightning • Cloud to Ground Lightning • 20% of lightning strokes • Most damaging and dangerous • Flash is made up of individual strokes • Leader, step leader, return stroke, and dart leader
Tornadoes • AKA: twisters, cyclones • Violent windstorms that are a vortex • Contains lower pressure inside the vortex than the surrounding areas
Tornado Formation • Form in association with severe thunderstorms • Located wherever severe weather is: cold fronts, squall lines, hurricanes, supercells • Only tornado if funnel cloud touches surface
F-Scale • Fujita Intensity Scale • Determined based upon damage produced
Tornado Forecasting Watches Warnings • Alters public to POSSIBLITY of tornadoes over a specific area for a certain time period. • 65,000sq.km for 4-6 hours • Issued by local NWS • ACTUAL sighted tornado in an area or indicated by radar • Smaller areas and for shorter periods of time