What conditions are perfect for making a tornado?

Answer 1

The formation of tornadoes is complicated.

First, a condition called wind shear, in which the speed and/or direction of the wind changes with altitude. If the shear is strong enough it can essentially tilt a thunderstorm, this separates the updraft and downdraft of the thunderstorm, preventing them from interfering with one another. This allows the storm to become stronger and last longer.

Additionally, if the wind shear is strong enough it can start the air rolling in what is called horizontal vorticity. This horizontal vorticity can then be turned vertical by a thunderstorm's updraft. When this happens, the thunderstorm may start rotating. The rotation is especially strong in an updraft called a mesocyclone. If the storm intensifies rapidly enough, a relatively warm downdraft called a rear-flank downdraft or RFD can wrap around the bottom part of the mesocyclone. This can then tighten and intensify its rotation and bring it down to the ground to produce a tornado. In addition to tornadoes, very heavy rain, frequent lightning, strong wind gusts, and hail are common in such storms.

Answer 2

Conditions most favorable tornadoes to form include atmospheric instability with warm, moist air in the lower atmosphere under cool air in the upper atmosphere and some sort of synoptic scale pattern such as a cold front or dry line to apply some weak to modest lift to the atmosphere to trigger convection that will eventually lead to thunderstorms (strong lift favors a different mode of thunderstorms less conducive to tornado formation). The next key ingredient is an inversion layer or cap of stable air a little more than a mile above the ground, this initially holds back the formation of thunderstorms, allowing instability to build. By later afternoon the heat of the day erodes the inversion layer and the storms break through. Because of the built up instability these storms will develop explosively and become very powerful with some storms having updrafts in excess of 100 mph. The next crucial ingredient is strong wind shear where the wind at higher levels is much stronger than lower level winds and in a different direction, this does three things to a thunderstorm. First, it tilts the storm separates the updraft from the downdraft so that they don't interfere with each other. Next it creates an upward pressure gradient that further strengthens the updraft, intensifying the storm even more. Finally, it sets the storm rotating, turning the updraft into a vortex called a mesocyclone. The final ingredient is a low lifting condensation level (LCL), meaning that the moisture in the air condenses into clouds at a fairly low altitude. In the final step of tornado formation a downdraft wraps around, tightens, and intensifies the mesocyclone to produce a tornado. A low LCL means a warm downdraft that will help maintain the updraft that powers the tornado. If the LCL is too high the downdraft will be cold and will inhibit formation. A low LCL generally comes from high relative humidity.

Answer 3

Here is an ideal setup for spawning tornadoes:

The setup begins with a hot, humid, unstable air mass capped by a stable mass about a mile or so up. Above that is cold, dry air The cap keeps storms from forming, so rather than firing off prematurely, the lower atmosphere just becomes hotter and more unstable as the sun heats the ground. As the day becomes hotter, the stable cap begins to weaken. As this is happening a low-pressure system comes in from the west. Coming with it is a mass of cooler air. Since the cooler air is denser, it will force the hot air up. This upward push causes strong thunderstorms to develop in the highly unstable air. At the same time, the system interacts with the jet stream, creating a setup of wind shear, with upper-level winds blowing much faster and in a different direction than the wind at the ground. The shear sets the thunderstorms rotating, turning them into supercells. As a supercell reaches its peak intensity, a downdraft may come around the back of the the storm and wrap around the rotating updraft or mesocyclone, causing it to tighten, intensify, and stretch toward the ground to form a tornado. Since an ideal setup typically produces multiple supercells, and a supercell can produce multiple tornadoes, the likely outcome here is not a single tornado, but an outbreak of tornadoes.