what causes tornadoes?

Answer 1

Big differences in temperature between the front edge and back edge of a frontal system. We just had one up here in Minnesota. The temperature before the storm struck was about 80 degrees, after the storm passed it was in the 50's.

Answer 2

Most tornadoes follow a recognizable life cycle. The cycle begins when a strong thunderstorm develops a rotating mesocyclone a few miles up in the atmosphere, becoming a supercell. As rainfall in the storm increases, it drags with it an area of quickly descending air known as the rear flank downdraft (RFD). This downdraft accelerates as it approaches the ground, and drags the rotating mesocyclone towards the ground with it.

As the mesocyclone approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause damage a good distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within minutes of the RFD reaching the ground.

Initially, the tornado has a good source of warm, moist inflow to power it, so it grows until it reaches the mature stage. During its mature stage, which can last anywhere from a few minutes to more than an hour, a tornado often causes the most damage, and can in rare instances be more than one mile across. Meanwhile, the RFD, now an area of cool surface winds, begins to wrap around the tornado, cutting off the inflow of warm air which feeds the tornado.

As the RFD completely wraps around and chokes off the tornado's air supply, the tornado begins to weaken, becoming thin and rope-like. This is the dissipating stage, and the tornado often fizzles within minutes. During the dissipating stage, the shape of the tornado becomes highly influenced by the direction of surface winds, and can be blown into fantastic patterns.

As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it. In particularly intense supercells, tornadoes can develop cyclically. As the first mesocyclone and associated tornado dissipate, the storm's inflow is concentrated into a new area closer to the center of the storm. If a new mesocyclone develops, the cycle may start again, producing a new tornado. Occasionally, the old, or occluded mesocyclone, and the new mesocyclone produce a tornado at the same time.

Though this is a widely-accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as landspouts, long-lived tornadoes, or tornadoes with multiple vortices. These each have different mechanisms which influence their development—however, most tornadoes follow a pattern similar to this one.

Tornadoes can be the most destructive storms on earth. Most have winds of 110 mph (175 km/h) or less, are approximately 250 feet (75 meters) across, and travel a few miles (several kilometers) before dissipating. However, some tornadoes can have winds of more than 300 mph (480 km/h), be more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 kilometers).

They have been observed on every continent except Antarctica; however, a significant percentage of the world's tornadoes occur in the United States. This is mostly due to the unique geography of the country, which allows the conditions which breed strong, long-lived storms to occur many times a year. Other areas which commonly experience tornadoes are Australia, south-central Canada, northwestern Europe, south-central and eastern Asia, east-central South America, and South Africa.

Answer 3

tornadoes is cause by the mixing of warm and cold air that spins around. if it can go just enough speed, it will touch the ground, and becoming a tornado.

another way is the wind stream hit a cloud of warm and cold air and starts to spin, and that way it becomes a tornado.

Answer 4

Tornadoes form in unusually violent thunderstorms when there is sufficient (1) instability, and (2) wind shear present in the lower atmosphere. Instability refers to warmer and more humid than usual conditions in the lower atmosphere, and possibly cooler than usual conditions in the upper atmosphere. Wind shear in this case refers to the wind direction changing, and the wind speed increasing, with height. An example would be a southerly wind of 15 mph at the surface, changing to a southwesterly or westerly wind of 50 mph at 5,000 feet altitude.

This kind of wind shear and instability is usually exists only ahead of a cold front and low pressure system. The intense spinning of a tornado is partly the result of the updrafts and downdrafts in the thunderstorm (caused by the unstable air) interacting with the wind shear, causing a tilting of the wind shear to form and upright tornado vortex. Helping the process along, cyclonically flowing air around the cyclone, already slowly spinning in a counter-clockwise direction (in the Northern Hemisphere), converges inward toward the thunderstorm, causing it to spin faster. This is the same process that causes an ice skater to spin faster when she pulls her arms in toward her body.

Other processes can enhance the chances for tornado formation. For instance, dry air in the middle atmosphere can be rapidly cooled by rain in the thunderstorm, strengthening the downdrafts that are needed for tornado formation. Notice that, in virtually every picture you see of a tornado, the tornado has formed on the boundary between dark clouds (the storm updraft region) and bright clouds (the downdraft region), evidence for the importance of updrafts and downdrafts to tornado formation. Also, an isolated strong thunderstorm just ahead of a squall line that then merges with the squall line often becomes tornadic; isolated storms or more likely to form tornadoes than squall lines, since an isolated storm can form a more symmetric flow pattern around it and also have less competition for unstable air "fuel" than if it were part of a solid line of storms.

Because both instability and wind shear are necessary for tornado information, sometimes weak tornadoes can occur when the wind shear conditions are strong, but the atmosphere is not very unstable. This sometimes happens in southern California in the winter, for instance, when a strong low pressure system comes ashore. Similarly, weak tornadoes can occur when the airmass is very unstable, but has little wind shear. For instance, Florida has many weaker tornadoes of this variety. Of course, the most violent tornadoes occur when both strong instability and strong wind shear are present.

Interesting facts:
TORNADO COUNTRY The United States experiences more tornadoes than anyplace else in the world. A few other countries that experience especially violent tornadoes include India, Bangladesh, and Argentina. It is estimated that over 95% of all tornadoes spin cyclonically (counter-clockwise). Oddly, the very first recorded film of a tornado was of one that was spinning in the other direction(!)

Answer 5

This is covered by the Tornado FAQ hosted at NOAA's Storm Prediction Center webstie. This is the place that issues, among other things, tornado watches.

http://www.spc.noaa.gov/faq/tornado/

Answer 6

Extreme disturbances caused by squall lines that form between masses of high and low air pressure that form along squall lines with severe thunderstorms.

Answer 7

they originate from the gas given off when acorns get very wet from excessive rainfall. That is why you never hear of tornadoes during a dry spell.

Answer 8

different temperatures between two areas.