TORNADO
What is a Tornado?
A tornado is "a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud".
Funnel cloud
A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (as described by Bernoulli's principle) and rapid rotation (due to cyclostrophic balance) usually causes water vapor in the air to condense into cloud droplets due to adiabatic cooling. This results in the formation of a visible funnel cloud or condensation funnel.
Rotation
While large-scale storms always rotate cyclonically due to the Coriolis effect, thunderstorms and tornadoes are so small that the direct influence of the Coriolis effect is unimportant. Supercells and tornadoes rotate cyclonically in numerical simulations even when the Coriolis effect is neglected. when viewed from above, this is counterclockwise in the northern hemisphere and clockwise in the southern)
Cause of tornado
The truth is that we don't fully understand. The most destructive and deadly tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. (Supercells can also produce damaging hail, severe non-tornadic winds, unusually frequent lightning, and flash floods.)
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supercell tornado
Tornadoes that come from a supercell thunderstorm are the most common, and often the most dangerous. A rotating updraft is a key to the development of a supercell, and eventually a tornado. There are many ideas about how this rotation begins. One way a column of air can begin to rotate is from wind shear – when winds at two different levels above the ground blow at different speeds or in different directions. As few as 20 percent of all supercell thunderstorms actually produce tornadoes.
Tornadoes often develop from a class of thunderstorms known as supercells. Supercells contain mesocyclones, an area of organized rotation a few miles up in the atmosphere, usually 1–6 miles (2–10 km) across. Most intense tornadoes (EF3 to EF5 on the Enhanced Fujita Scale) develop from supercells. In addition to tornadoes, very heavy rain, frequent lightning, strong wind gusts, and hail are common in such storms
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nonsupercell tornado
Non-supercell tornadoes are circulations that do not form from organized storm-scale rotation. These tornadoes form from a vertically spinning parcel of air already occurring near the ground caused by wind shear from a warm, cold, or sea breeze front, or a dryline. When an updraft moves over the spinning, and stretches it, a tornado can form.
One non-supercell tornado is the gustnado, a whirl of dust or debris at or near the ground with no condensation funnel, which forms along the gust front of a storm. Another non-supercell tornado is a landspout. A landspout is a tornado with a narrow, rope-like condensation funnel that forms while the thunderstorm cloud is still growing and there is no rotating updraft.
wind shear
Some storms get stronger because of wind shear, when winds at higher altitudes move faster and in a different direction than winds at lower altitudes. Wind shear makes the storm tilt and rotate.
Scale of tornado
EF-0 light damage: Branches broken off trees; minor roof damage
EF-1 moderate damage: Tree snapped. Mobile home pushed off foundations; roofs damaged.
EF-2 consider damage: Big trees get toppled; Mobile homes are destroyed.
EF-3 severe damage: trains are overturned; Cars lifted off the ground; the walls of strong build homes blown away.
EF-4 devastating damage: Structures with weak foundations are blown away; cars become missiles flying in the air.
EF-5 incredible damage: Strongly built homes completely blown away