Characteristics and sources of tornadoes

What is a tornado

Tornadoes are powerful whirlwinds that occur primarily during the summer months in warmer regions of the United States, Europe, and Northeast Asia.

Generated primarily from cumulonimbus clouds, these winds are often accompanied by thunderstorms, sometimes with hail.

Unlike typical whirlwinds, tornadoes are incredibly large, sometimes reaching hundreds of metres in diameter. They cause great damage to life and property in many areas.

Wind speeds are often recorded at over 180 kilometres per hour, and their size and intensity varies from region to region.

To measure their strength, the Fujita scale was previously used, but in 2007, a revised Fujita scale was introduced, with ratings ranging from EF0 to EF5.

The higher the number on the scale, the more powerful the tornado.

The specific conditions under which tornadoes develop are believed to be similar to thunderstorms, but the exact causes and mechanisms of their creation are still not fully understood.

These areas are still a subject of research for scientists and remain a great deal of mystery.

Structure and features

Tornadoes occur mainly in temperate regions with average annual temperatures between 10-20°C, and are much less likely to occur in the tropics.

They take the form of a columnar vortex of air that spins violently almost vertically, and are accompanied by much stronger winds than typhoons.

In fact, instantaneous wind speeds can exceed 150 m/sec.

The air around the columnar vortex is sucked into the centre, causing a rapid drop in barometric pressure, which results in adiabatic cooling, causing water vapour to condense and form a funnel-shaped cloud.

However, in very dry areas, a funnel-shaped cloud may not form, and sometimes the funnel cloud does not reach the ground at all.

Tornadoes are relatively small-scale weather events, but their rotation is largely driven by low pressure.

At the point of contact with the ground, the air being sucked in twists into a spiral and rises.

This direction of rotation is due to the fact that the cloud that forms the tornado is itself undergoing a low-pressure rotation.

Funnel clouds usually move at speeds of 100 m/s to 200 m/s, but they have been observed to move at speeds of 250 m/s.

Most tornadoes are short-lived, and statistically speaking, tornadoes that occur in the United States often terminate their paths within 30 to 50 kilometres, but there are exceptions, such as tornadoes that travel more than 400 kilometres.

How tornadoes are created

Tornadoes basically form when turbulent winds collide with cold and warm winds.

In typical areas of the United States and Canada, when cold air from above meets warm air from below, the two swirl around each other to form a tornado.

Also, one of the conditions that make tornadoes more prone to occur is the need for large areas of plains. In these plains, the wind can move freely without obstacles, which promotes the formation of tornadoes.

On the other hand, when the wind encounters mountains, the mountain ranges impede the flow of wind, and the wind loses much of its original power as it crosses the mountains.

On the other hand, in mountainous regions such as South Korea and Japan, not only these topographical features but also climatic factors inhibit the development of tornadoes.

In both countries, warm winds blow irregularly, making it difficult for tornadoes to form. This combination of climate and topography is one of the main reasons why tornadoes occur less frequently.

Scale and damage

Tornadoes are classified on a scale of EF0 to EF5, depending on their strength. While an EF0, or least powerful, tornado can snap a tree branch or damage a sign, an EF5, or highest-rated tornado, is incredibly destructive.

They can lift cars into the air, pull 83 tonne locomotives, and even capsize ships and blow away large passenger aircraft. For example, a 1931 tornado in the US state of Minnesota is said to have lifted an 83-tonne locomotive.

Most tornadoes roll at 600 km/h, but on 22 April 1759, a tornado is recorded to have passed at 500 km/h, destroying houses.

Tornadoes are at their most powerful when their funnel clouds hit the ground.

Their sound is similar to that of a jet flying overhead, and they can uproot trees, causing considerable destruction to their surroundings.

They can also blow off roofs and levitate cars, causing them to collapse. What’s more, it’s not just one tornado that strikes, but several at the same time, causing significant damage. In particular, the tornado outbreaks in the United States on 3 and 4 April 1974 were responsible for 320 deaths and thousands of injuries.

Because of their relatively small size, tornadoes can go unrecorded if they occur in uninhabited areas.

The number of tornadoes per year depends on population density and local interest in tornadoes. U.S. statistics since 1960 show that there are between 500 and 900 tornadoes per year.

The deadliest tornado in the United States occurred in March 1925, when it passed through Missouri, Illinois, and Indiana, killing 689 people.

The tornado had a path of 350 kilometres, a width of 1.5 kilometres and speeds of 100 kilometres per hour.

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