waht are the physical and climatic reasons for cyclones?

Answer 1

Temperature inversions. Hot air rises and cold air sinks. Normally they pass through each other, but sometimes the atmosphere just flips over pretty fast. Sorry I don't know the circumstances, but I think it has to do with the proximity of of high density air masses.

Answer 2

I'm not exactly certain what you're looking for, but I bet the answer is somewhere inside this quote:

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Most tornadoes follow a recognizable life cycle.[6] The cycle begins when a strong thunderstorm develops a rotating mesocyclone a few miles up in the atmosphere, becoming a supercell. As rainfall in the storm increases, it drags with it an area of quickly descending air known as the rear flank downdraft (RFD). This downdraft accelerates as it approaches the ground, and drags the rotating mesocyclone towards the ground with it.

As the mesocyclone approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. As the funnel decends, the RFD also reaches the ground, creating a gust front that can cause damage a good distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within minutes of the RFD reaching the ground.

Initially, the tornado has a good source of warm, moist inflow to power it, so it grows until it reaches the mature stage. During its mature stage, which can last anywhere from a few minutes to more than an hour, a tornado often causes the most damage, and can in rare instances be more than one mile across. Meanwhile, the RFD, now an area of cool surface winds, begins to wrap around the tornado, cutting off the inflow of warm air which feeds the tornado.

As the RFD completely wraps around and chokes off the tornado's air supply, the tornado begins to weaken, becoming thin and rope-like. This is the dissipating stage, and the tornado often fizzles within minutes. During the dissipating stage, the tornado becomes highly influenced by the direction of surface winds, and can be blown into fantastic patterns.

As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it. In particularly intense supercells, tornadoes can develop cyclically. As the first mesocyclone and associated tornado dissipate, the storm's inflow is concentrated into a new area closer to the center of the storm. If a new mesocyclone develops, the cycle may start again, producing a new tornado. Occasionally, the old, or occluded mesocyclone, and the new mesocyclone produce a tornado at the same time.

Though this is a widely-accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as landspouts, long-lived tornadoes, or tornadoes with multiple vorticies. These each have different mechanisms which influence their development—however, most tornadoes follow a pattern similar to this one.
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