Tornadoes

Tornadoes Tornadoes –Violent windstorms that take the form of a rotation column of air called a vortex. The vortex extends downward from a cumulonimbus cloud. –A product of thunderstorms; rapidly rotating winds that blow around a small area of intense low pressure –Tornado circulation is present on the ground either as a funnel-shaped cloud or as a swirling cloud of dust & debris

Tornadoes An important process in tornado formation is the development of a mesocyclone. –A mesocyclone is a vertical cylinder of rotating air that develops in the updraft of a thunderstorm.

Formation of a Mesocyclone

Tornado Life Cycles Funnel cloud Tornado that hasn’t reached the ground Dust-whirl stage Swirling dust at the ground marks the tornadoes circulation Mature stage Funnel at greatest width, most intense damage. Often vertical Decay stage Funnel shrinks, damage becomes less, tornado becomes stretched Minor tornadoes may evolve only through certain stages

Fujita Scale Fujita Scale: Theodore Fujita in late 1960s --- classifying tornadoes according to their rotational wind speed based on the damage done by the storm Majority of tornadoes are F0 and F1 (weak ones) and only a few % are above the F3(violent) with ~ 1 F5/yr Tornado Formation: Tornadoes tend to form with intense thunderstorms and a conditionally unstable atmosphere is essential for their development Most strong and violent tornadoes develop near the right rear sector of a severe thunderstorm In order for a tornado to spawn, the updraft must rotate

The Fujita Scale Tornado classification based on damage

Seeking Shelter Tornado watch – tornadoes are likely to develop within the next few hours Tornado warning – issued once a tornado is spotted or indicated by radar.