| MadSci Network: Earth Science |
The honest answer to your question is that meteorologists aren't quite sure what causes tornadoes! There are a number of ideas, but because it is so difficult to see what happens very near and inside a tornado, these ideas cannot be confirmed very easily. Although all tornadoes may look the same (a rapidly spinning vortex that reaches the ground), our limited observations indicate all of them probably don't form the same way. Most of the devastating tornadoes that occur are associated with a spinning thunderstorm called a supercell. These supercells spin because the air that they suck up from the ground already is spinning in some sense. The process by which the tornado appears to descend from the supercell is still a mystery. Meteorologists use computers and observations to test ideas about how this process occurs. After studying this data, some meteorologists think that there is an interaction between the column of air that is moving upward within the storm, called an updraft, and a column of downward moving air, called a downdraft. Because these airflows are typically located next to one another in a supercell, they may interact with one another. It is this interaction that some meteorologists think causes the air to spin faster, descend to the ground, and create a tornado.
This is just one idea, although it is an idea that matches some things that have been observed. To learn more about severe storms, you should visit the National Severe Storms Laboratory's homepage.
We do no have any information about the tornado that occurred in Mexico.