* Severe Thunderstorm : when this has been issued for your area, at that time, there are no severe thunderstorms. The T-storm watch simply means that the conditions of the atmosphere are suitable for the formation of thunderstorms containing strong winds, dangerous lightning, and possibly hail.
* Severe Thunderstorm : when this has been issued for your area, you should stay indoors, and away from any windows in the house (it also helps to close the drapes to slow the progression of flying glass if a window happens to break). You should do this simply because the conditions outside are very dangerous. There is heavy wind, lightning, and hail associated with severe thunderstorms.
* Tornado : this means that conditions in the atmosphere are suitable for the formation of tornadoes, not that there is a tornado already on the ground. When this has been issued, you should pay attention to weather reports to keep informed regarding the formation of tornadoes throughout the day.
* Tornado : A tornado warning for your area means that there is a tornado on the ground, or a possible tornado has been indicated by doppler radar, or there is a funnel cloud in your area. This is a very serious situation.
THIS IS WHAT NOT TO DO IN CASE OF A TORNADO:
DO NOT OPEN YOUR WINDOWS, yeah...you heard it right. Opening the windows is your house will not help your house in any way. If a tornado is near enough to effect the pressure of your house in any way, that's the least of your worries, because the tornado is probably right on top of you. Anyways, taking the time to open your windows just takes time that you could use finding adequate shelter.
DO NOT TRY TO OUTRUN OR OUTDRIVE A TORNADO. Tornadoes can travel an excess of 90 MPH. The best thing to do is find the nearest shelter or ditch and GET LOW.
2. Tornado Science
* The table on the main page list the five categories that tornadoes are grouped into according to wind speed. Most tornadoes in the US are in the F0-F2 range, which are relatively weak (but nonetheless deadly) tornadoes. Here are some actual stats on frequency:
Weak Tornadoes
69% of all tornadoes represent weak tornados. Lifetime is about 1-10+ minutes.
Strong Tornadoes
29% of all tornadoes represent strong tornadoes. Can last 20 minutes or longer.
Violent Tornadoes
Only 2% of all tornadoes. Lifetime can exceed 1 hour.
* The most powerful tornadoes are spawned by what are called supercell thunderstorms(illustrated right). These are storms, that under the right conditions, are effected by horizontal wind sheers (winds moving in different directions at different altitudes) . These wind sheers cause horizontal columns of air to begin to rotate the storm. This horizontal rotation can be tilted vertically by violent updrafts, and the rotation radius can shrink, forming a vertical column of very quickly swirling air. This rotating air can eventually reach the ground forming a tornado.
* The wall cloud is most likely the size and location of the rotating updraft formed in supercell thunderstorms. Because there are updrafts (air moving upward), surrounding air must rush in at the surface to replace the air that was lifted (this is what causes wind in any thunderstorm). Because this air is so moist due to it's rain saturated nature, it tends to reach it's dew point rather quickly when IT is pulled upward and results in a lower cloud base, called the wall cloud. Because, (as mentioned right) the updraft of the supercell is located in the same region as the wall cloud, this is the area of the supercell where tornadoes tend to originate from.
* Areas of the United States where warm tropical air masses and cold arctic air masses tend to collide frequently are much more likely to experience tornadoes. This area in the United States is nicknamed (map below)
The bright red is "TORNADO ALLEY".
* Most tornadoes occur in the spring months. These are months when the battle between warm and cold air is most active.
3. Tornado Myths
* Tornadoes do not travel in straight lines. Many times they move very quickly and turn and weave at very unpredictable times. This should serve as a warning to anyone who observes a tornado. Although it may look as if it is moving away or it is at a large distance away, it could turn at any moment and put YOU in harm's way.
* Tornadoes do not transport you to the mystical Land of Oz, they WILL kill you.
* and with no remorse.
* Tornado chasers don't get close enough to touch a twister (like in the movie Twister).
* That would be stupid. Flying debris will quickly kill anyone that gets as close to tornadoes as the people in Twister did (it's a movie after all, so be careful).
