what causes a tornado and what makes it stop?
481590
Tornadoes are created from severe Thunderstorms. They occur when a high pressure front meets head on with a low pressure front. No where is this more evident than in our mid-west, otherwise known as tornado alley, from the Canadian provinces to the Gulf of Mexico. Here, the Siberian express from Canada meets the warm tropical front from the Gulf of Mexico.
198999
I don't think tornados have a preference. It seems they like either one, especially if there's a trailer park! Seriously though, they can happen anywhere when cold air meets warm air. That's all I know about how they're formed. \nBut, from watching the weather reports about tornadoes in "Tornado Alley", I've noticed it doesn't matter if areas are incorporated or unincorporated. However, if it is unincorporated, there's definitely a lot less damage to structures (buildings). But even in an unincorporated area, buildings can be smashed.
858929
I don't live in U.S.A., but I can't tell you for sure that the tornados aren't named as hurricanes or typhoons. A tornado has a scale of intensity. The Fujita Scale. A tornado is classified as Category F0 to F5. A tornado F0 is a tornado that produces light damage. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged. The wind speed has to be less than 76 mph. A F1 tornado has some moderate damage. The lower limit is the beginning of hurricane wind speed (73 mph); peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed. The maximum limit is 112mph. A F2 tornado produces considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated. It's classified between 113 and 157 mph. A F3 tornado has severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown. Wind speed parameters are between 158 and 206 mph. A F4 tornado produces devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated. The winds blow between 207 and 260 mph. Finally, a F5 tornado has an incredible damage. Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 m (100 yd); trees debarked; steel reinforced concrete structures badly damaged; incredible phenomena will occur. That's all. I hope that this helped you.
396017
In the US Midwest, tornadoes are usually formed when a cold, dry air mass moving south from Canada collides with a warm, moist air mass moving north from the Gulf of Mexico (or Baja California, or the Atlantic, or what have you). \nThis produces large thunderstorm clouds known as supercells, which can produce heavy rains, hail, and tornados. \nTornados are formed in areas of the supercell called mesocyclones; which draws air into the storm. When you hear meteorologists talk about the "hook echo" on the radar, they're pointing out the mesocyclone. The best simple explanation (so far) for why the tornado starts to rotate is the phenomenon of vertical wind sheer, where wind changes direction at different elevations.\nSo, if you have access to a weather radar; you can see hook echos like the one below. If you have a wind velocity view (some do, some don't), look for a large difference in wind speed and direction around that hook echo.
11502
In order for a tornado to form, a number of different things have to happen. The first thing that has to happen is that you have to have two different patches of air moving toward each other from opposite directions, with a warm one on the bottom and a cool one on the top.\n\nThe next thing that happens is that the warm air rises. (You may have learned about hot air rising in school.) After the warm air goes up, the cool air comes down to take its place. So now the warm and cool patches of air are moving side to side and up and down. So they make a spinning patch of air along the ground. This is probably pretty hard to imagine, so check out the picture:\n\nUsually when a tornado is starting, it happens during a storm. So there's lots of air moving around already. If a draft of air from the storm comes along close to the ground and then moves upwards (called an "up-draft"), it will pull the spinning air upwards.\n\nNow comes the part that we don't understand quite as well. So far the spinning air is still really really wide. Somehow it gets pulled in really tight so that it makes a tornado. (Scientists aren't exactly sure why this happens sometimes but not at other times.)
982259
They are very rare, but I think as long as there is cold air clashing with warmer air (which can happen even in the winter), you can create conditions favorable to tornado developement. We had a severe snow storm in which we had thunder and lightning, the sky even turned slightly yellow....scary.
144997
A weather element is/can be a weather factor. For instance, the weather element of warm moist air blending with the weather element of cold dry air can be weather factors in producing a tornado.\n\nElement = A Single item\nFactor = A Single item considerred a contributor to an event.
860876
Well winds in a tornado can reach speeds of 300 mph, this in itself is enough to cause total destruction.\n\nPressure is also lowest at the center of a hurricane, or any other low-pressure system. The air is being pulled up away from the ground and thus the pressure is low.
365692
The US averages around 900 tornadoes per year.\n\nSome years it is much higher. Increased hurricane activity sometimes causes a rise in tornadoes reported. So particularly active hurricane seasons will cause there to be more than normal.\n\n:)
975582
You can't tell by just stepping outside, unless you see a funnel cloud or something.  Tornadoes are usually created from cold fronts or occluded fronts.  You have very warm air ahead of the front, and very cool air behind it.  The difference in the air temperature pushes air up, creating an updraft.  Bottom line, tornadoes are caused by warm and cool air in the same area.  And you have to have very strong winds in the upper atmosphere.  70 to 80 mph.  That helps with the updraft.
1130792
tornados have a much higher wind scale than hurricanes do.  an F5 tornado has winds up to 318mph.  hurricanes go up to category 5.  a category 5 has winds higher than 155mph, but I've never heard of one that's had winds higher than 200mph.  it's a misconception that hurricanes cause more damage b/c of their sheer size, but the most damaging part of a hurricane is the Northeast side of the storm.  whereas a tornado is damaging no matter where it hits you b/c it just sucks everything right on up and can go on for miles and miles.  hurricanes almost always weaken when they completely come ashore.
13162
Actually, scientists understand a lot about tornadoes, but cannot completely predict them because they happen on such a micro-scale compared to other weather phenomenae.  Scientists can predict when conditions are favorable for tornadic activity (like when a tornado warning is issued), but can't predict excatly where one will occur until moments before hand.
929539
wind is caused by the movement of air from regions of high atmospheric pressure to regions of low atmospheric pressure.  high pressure is caused by the cooling of air: as air cools, it shrinks and becomes more dense and its pressure therefore increases.  low  pressure is caused by the heating of air: as air warms, it expands and becomes less dense and its pressure therefore decreases.\nrain is caused by the rising of columns of air: when a bubble of air is warmer than its surroundings, it expands and becomes less dense.  this less dense air rises, and as it rises, it gets cooler.  as it cools, it becomes less able to hold moisture.  eventually, you reach a point at which the air can no longer get any cooler without having to lose some moisture.  it is at this point that clouds and rain start to form.\nyou get storms if you have the right combination or rain, wind, air pressure, humidity, and clouds.
677757
Often wind damage that's blamed on tornadoes is actually done by winds coming down from a shower or thunderstorm. \nSuch "microburst" winds can reach more than 150 mph. In a tornado, the air is rising as it swirls around the vortex.\n\nIn the U.S. such microbursts are common from the Western Rockies eastward.. why? because that is where the rains are more prevalent
164145
In the U.S., it is due to cold dry air from over the Rocky Mountains mixing with warm moist air from the Gulf of Mexico.  Most tornadoes occur in the summer, which is when the air from the Gulf of Mexico is hottest, so it provides the most energy at that time of the year.  And "Tornado Alley" consists primarily of those states positioned between the Gulf and the Rockies.
710530
Several reasons\n1) A hurricane is larger and covers more area while a tornado is much smaller and may only hit one house and leave the neighbors house.  A hurricane can be 500 miles wide, while a tornado is 2 miles wide at most.\n2) A hurricane has storm surge and flooding rains, while a tornado is usually rainless.  A tornado can do more damage to one particular location, but hurricanes have widespread damage.
565442
That sounds like an interesting topic.  Here are some good websites (I tried to pick reputable ones) to help you get started.  Good luck on your portfolio.\n\nhttp://www.noaa.gov/tornadoes.html\nThis one has a good summary of what a tornado is, where and when they occur, and explains the scale used to rate tornadoes.  It's got many links to other helpful sites too.\n\nhttp://www.wildwildweather.com/twisters.htm\nThis site has a lot of good info on how tornadoes form and also has a lot of images of tornadoes and people who chase them.\n\nhttp://www.weatherwizkids.com/tornado.htm\nThis site is geared towards younger audiences, it's very good at explaining tornadoes and many facts about them.