qOccur when
winds exceed 93 km/hr
(58 mph), have large hailstones
(1.9 cm; 0.75 in) or produce
tornadoes.
qThese systems
differ from air mass thunderstorms
in that the up and downdrafts
support each other to intensify
the storm.
qParticular
atmospheric conditions must persist across the mesoscale (10-1000 km) for severe thunderstorms to develop.
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