Manitoba Tornado

What is a Tornado?

     Well, for starters, the denotative meaning of tornado is, "a localized, violently destructive windstorm occurring over land, especially in the Middle West, and characterized by a long, funnel-shaped cloud extending toward the ground and made visible by condensation and debris." But, in more user friendly terms, a tornado is a large swirling air mass that is very destructive. The slowest a tornado can be to be considered a tornado is an F0 at40mph. The fastest one clocked was a F5 at 318mph. Tornadoes are categorized on the Fujita Scale which follows as so:

F-Scale Number	Intensity Phrase	Wind Speed	Type of Damage Done
F0	Gale tornado	40-72 mph	Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards.
F1	Moderate tornado	73-112 mph	The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed.
F2	Significant tornado	113-157 mph	Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated.
F3	Severe tornado	158-206 mph	Roof and some walls torn off well constructed houses; trains overturned; most trees in fores uprooted
F4	Devastating tornado	207-260 mph	Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.
F5	Incredible tornado	261-318 mph	Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel re-inforced concrete structures badly damaged.
F6	Inconceivable tornado	319-379 mph	These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F6 damage. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies

      The word "tornado" comes from the Latin word, tornare, meaning "to thunder." The Spanish developed the word into tornear, meaning to turn or twist. Thus, giving the tornado the nickname "twister" or "cyclone." Who knew etymology could be so fun!
     A tornado is a powerful column of winds spiraling around a center of low atmospheric pressure. It looks like a large black funnel hanging down from a storm cloud. The narrow end will move over the earth, whipping back and forth like a tail. The winds inside a tornado spiral upward and inward with a lot of speed and power. It crates an internal vacuum that then sucks up anything it passes over. When the funnel touches a structure, the fierce winds have the ability to tear it apart.

How Long can a Tornado Last, and How Fast do They Move?

     Tornadoes can last from a few seconds to more than an hour. They might remain on the ground for just a few yards or for more than 100 miles. On average, tornadoes move from the southwest to the northeast at about 30 mph. However, as the killer Jarrell, Texas, tornado of May 27, 1997, showed, tornadoes can defy these averages. The "F-5" tornado that killed 27 people when it churned through a Jarrell subdivision moved southwest at only 10 mph. Tornadoes have been known to move in any direction at speeds up to 70 mph. Some have sat nearly stationary for several minutes. But, it is unusual for tornadoes to change speed and direction during their lifetime.
     The winds inside a twister can spin around at speeds up to 500 miles an hour, but usually travels at roughly 300 miles an hour. This makes the tornado the most dangerous storm known to mankind. Because of the earth’s unique weather system, twisters rotate counterclockwise in the Northern Hemisphere and move eastward. They rotate clockwise in the Southern Hemisphere. Tornadoes also often come with hailstorms.
     Many storms create harmless funnels that never touch earth. They can last from a few seconds to a few hours. Others disappear and reappear minutes later. The average tornado has a diameter of about 200 to 300 yards, and some grow large enough to spawn smaller tornadoes known as satellite tornadoes. These small offspring, about 50 yards across, can be very fierce and do lots of damage. They also tend to branch away from the parent funnel, taking separate paths across the earth.
     It can travel across the ground at high speeds, then just as suddenly vanish. They can kill in a matter of seconds. Every year, about $500 million worth in damage is done by twisters in the United States. Most tornadoes last less than twenty minutes and travel less than 15 miles. However, superstorms sometimes occur, traveling over 100 miles before they are exhausted. Although they don’t occur very often, they are responsible for 20% of all tornado casualties.

What are the Perfect Conditions for Tornadoes?

     What time do they form?
               Tornadoes can form at any time of year, but the conditions are most favorable in May. This is your basic "Tornado Season". On the Gulf Coast, it's earlier in the spring, but in the northern plains and upper Midwest, the season is late June and July. They also can occur at any time of day, but happen between 4-9 p.m.
     Where do tornadoes form?
               Most tornadoes occur right smack dab in the middle of the United States. This strip of the U.S is called "Tornado Alley".  The states in Tornado Alley are North Dakota, South Dakota, Minnesota, Iowa, Montana, Indiana, Illinois, Ohio, Nebraska, Colorado, Kansas, Missouri, Kentucky, Tennessee, Oklahoma, Louisiana, Arkansas, and last but not least (by a long shot), Texas!
     How do tornadoes begin?
               Tornadoes begin in a severe thunderstorm called a "Supercell," which forms when a cold air mass and a warm air mass collide. Supercells last longer than your run-of-the- mill thunderstorm. The same property that keeps the storm going, also produces most tornadoes. Winds coming into the storm starts to swirl and form a "Funnel Cloud". The air in the Funnel Cloud spins faster and faster, creating low pressure around it. This sucks more air (and possibly objects) into it! (Hey! It's Bernoulli's Principle!!!)