Tornadoes

It is not known. For one thing, most countries do not keep records of their tornadoes, and even the United States, which keeps the best records, only has accurate record going back a few decades. Real numbers are not known, but in all likelihood there are several thousand tornadoes in the world each year. These have likely been occurring since Earth was cool enough for thunderstorms, which is a span of over 4 billion years. The activity has likely varied with the climate but we can probably say that, in its entire history, Earth has had several hundred billion to several trillion tornadoes.

It you want to get very technical, they occur in the U.S. and Canada, as these are the only two countries that use the Enhanced Fujita scale. However, if you consider tornadoes of equivalent intensity (F3 on the Fujita scale, T6 and T7 on the TORRO scale), they can occur in most areas that have a temperate to tropical climate that is not arid. In the U.S. all but six of the states have had at least one F3 or EF3 tornado since 1950. Many countries have tornadoes that go unrated that are almost certainly of EF3 intensity, if not higher. The majority of EF3 and stronger tornadoes occur in the U.S.

Yes. The duration of a tornado is measured in minutes, and a tornado is usually not over any given spot for more than a few seconds.

Tornadoes are not uncommon on the prairies of Canada because they experience some of the same effects that have led to the high incidence of tornadoes in Tornado Alley to the south. Some even consider the southern portion of these plains to be part of Tornado Alley. In this region it is not uncommon to have collisions of warm, moist air from the Gulf of Mexico, cool air from northern Canada, and dry air from the Rockies. These collisions result in very strong thunderstorms, with the moist air acting as their "fuel." Additionally, the region often has a layer of stable air called a cap that suppresses storms. This behaves like the lid on a pressure cooker, allowing the atmosphere below it to become increasingly unstable until storms develop explosively. Finally, the region often sees strong vertical wind shear, or a variation of wind speed and direction with altitude. This tilts them in such a way that the updraft and downdraft portions becomes separated and don't interfere with one another, letting the already strong storm further strengthen and last longer. The wind shear also sets the storms rotating, turning them into supercells, the most powerful thunderstorms on earth. It is the rotation within these supercells that can develop into a tornado.

The actual amount of damage can vary considerably. Typical EF1 damage might include severe damage to roofs with some poorly secured roofs torn off. Gutters and awnings are taken down and some windows may break. Some barns, garages, and outbuildings may be destroyed. Trailer homes are likely to be badly damaged or overturned. Many trees may be downed. Note that the rating of a tornado is based on the most severe damage it causes. Many EF1 tornadoes cause mostly EF0 damage with perhaps one or two buildings suffering EF1 damage. In terms of the amount, damage can range from a few downed trees or a single damaged home to many dozens of homes damaged. Damage costs are often in the tens to hundreds of thousands of dollars, but can reach into the millions on occasion.

Tornadoes hit Oklahoma every year.

Yes. Tornadoes can occur at any time of day or night.

Yes. A tornado is a violent weather event.

There were many tornadoes in 1925, but you are most likely referring to the infamous Tri-State tornado. The number of survivors is not known, as we do not know how many people were in the path. The number is likely in the thousands or tens of thousands. At least 2,000 survived with injuries.

The process of tornado formation generally begins in a rotating mass of air within a mesocyclone, a rotating mass of air in a type of thunderstorm called a supercell. A downdraft wraps around the mesocyclone, causing it to tighten and intensify, while at the same time stretching to extend downward. This process usually begins two or three miles above ground level. If the intense vortex reaches the ground, it is considered a tornado.

Tornadoes have incredibly powerful winds that are capable of moving things that wind normally wouldn't be able to move. Since there is a significant upward component to the wind's direction, objects tend to be lifted. This can include people, cars and, on rare occasions, houses.

The tornado would go up one side of the mountain and down the other without being significantly affected.

Yes. A tornado on water is called a waterspout.

You can get a general idea of a tornado's direction by watching it move. Note that if a tornado does not appear to be moving to either side but instead looks to be getting bigger, there's a good chance its coming straight at you.

Outside of visual observations, the movement of a tornado can be tracked by Doppler radar.

The united states averages between 1,200 and 1,300 tornadoes per year. If you are referring to a particular time period, please specify it.

The helicopter would most likely land and a field or some other flat area that is relatively free of debris.

The deadliest tornado in Bangladesh, in fact the deadliest in the world, was the Daulatpur-Saturia tornado of April 26, 1989. This tornado tore through cities in the Dhaka district, killing 1,300 people.

Tornadoes are a destructive force. They cause some erosion but do no build up any features.

It is impossible to predict where the next tornado will occur.

The strongest tornado officially listed to have hit Pinellas county was an F4 on April 4, 1966. However, more recent analysis that this event consisted of at least 3 tornadoes forming in succession. The actual F4 damage was in Polk County and so may have been from a later tornado in this family.

The is no Fajita scale. The Fujita scale provides basic standards by which to assess the damage done by a tornado. Based on the severity of the damage a tornado is assigned a rating, which can range from F0 for the weakest tornadoes to F5 for the strongest.

Tornado warings are issued when radar imagery or eyewitness reports indicate that a tornado has formed or is likely to form soon. A warning is then issued by the local offines of the National Weather service for people in the potential path. Information given includes where the tornado was at the last update, where it is going, how fast it is going, and area in the potential path. The warning is then broadcast through TV and radio providers. In some cases the local news stations may interrupt scheduled programming for these emergency broadcasts. Today people may also be alerted through apps on their phones. In some areas sirens will sound when a warning is issued.

A tornado warning is issued when radar data and eyewitness reports indicate a tornado has formed, is forming, or is likely to form soon. These warnings are then issued by the local office of the National Weather Service. The warning will contain information on the tornado's location, speed and direction of movement, and places in the potential path. This information is distributed through TV and radio stations as well as smart phone apps. In some places sirens may sound to alert people.

Yes. The rating of a tornado only refers to the worst damage that it causes. Usually only a small percentage of strucures in an EF5 tornado will actually be struck by EF5 winds. Many strutures will be hit by winds that are far less powerful but still capable of causing significant damage. In the aftermath of a tornado it is not uncommon to see houses and other buildings with exterior walls, including brick walls, collapsed while the rest of the structure remains mostly intact.