mesocyclones range in size mesoscale beta microscale. term mesocyclone reserved mid-level rotations within severe thunderstorms, , warm core cyclones driven latent heat of associated thunderstorm activity.
tornadoes form in warm sector of extratropical cyclones strong upper level jet stream exists. mesocyclones believed form when strong changes of wind speed and/or direction height ( wind shear ) sets parts of lower part of atmosphere spinning in invisible tube-like rolls. convective updraft of thunderstorm thought draw spinning air, tilting rolls orientation upward (from parallel ground perpendicular) , causing entire updraft rotate vertical column.
as updraft rotates, may form known wall cloud. wall cloud spinning layer of clouds descending mesocyclone. wall cloud tends form closer center of mesocyclone. should noted wall clouds not need mesocyclone form , not rotate. wall cloud descends, funnel-shaped cloud may form @ center. first stage of tornado formation. presence of mesocyclone believed key factor in formation of strong tornadoes associated severe thunderstorms.
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