T O R N A D O E S
does a tornado form?
- A tornado
gets its start when cold, dry air runs into warm moist air, which rises,
condenses into heavy rain, and then falls in powerful downdrafts. These
kinds of conditions are most often found in the Great Plains, where the
high altitude jet stream form the west encounters warm, moist air moving
north from the Gulf of Mexico, and warm, dry air from the southwest.
like supercell thunderstorms get their energy from a "mesocyclone",
a spinning updraft of air. What starts a mesocyclone rotating can be air
masses crossing over each other in different directions, or a faster upper
level stream rolling over a slower lower level stream.
- In both cases,
a mass of air begins to spin, and then rises upward. Unlike a regular thunderstorm,
a mesocyclone endures because it's tilted, and the cold downdraft
does not smother and dampen the warm updraft: this kind of storm
keeps growing and going!
don't yet know if a tornado's funnel grows from the storm cloud down to
the surface, or from the surface up, but many now think that cold air descending
in a downdraft gets sucked in by the rotating updraft, and adds its energy
to the incoming rising spiral of air.
- As the funnel
grows smaller, just like an ice-skater pulling in his or her arms, it spins
faster, resulting in the colossal wind speeds of 300 miles per hour or more.
The rapidly rising air makes the funnel like a mad vacuum cleaner sucking
up anything in its path.