Causes of Tornados

The sky is greenish-gray in color, heavy with thunderstorm clouds. Ominous masses of dark clouds begin collecting in the horizon. All of a sudden, a funnel-like tail emerges from one of them, twisting and spinning – the unmistakable beginnings of a tornado! It begins whipping to and fro as it starts moving over the earth, twisting and tearing away trees, houses, and anything else that comes in its path, with the enormous forces that the churning winds within it create. Tornados are indeed awesome spectacles of nature to watch from a distance, and the majority of them occur in the United States.

The tornados in the United States usually occur in the early spring, which is actually known as the ‘tornado season’. With increasing latitude, the season shifts in the later months. Hundreds of tornados occur in states such as Texas, Missouri, Oklahoma, Illinois, and Kansas. In fact, since they are so common in the south central and mid-western region of the United States, this area is popularly known as ‘tornado alley’.

Some of the atmospheric conditions that create tornados:

Thunderstorms develop when the air becomes warm and moist, in advance of cold fronts that move eastwards. These are the thunderstorms that usually produce strong winds, large sized hail, and tornados. The tornados that occur in the winter or early spring generally are associated with strong weather conditions that are created in the central states, which then move eastward. Sometimes, this kind of weather pattern creates a large number of tornados. A number of states can be affected by several powerful thunderstorms as well as tornados.

In the Central Plains, thunderstorms often develop in the spring along a dryline, which forms a dividing line between dry, hot air from the west and the moist, warm air from the east. As this dryline travels eastwards in the afternoon hours, it can lead to the formation of thunderstorms, which can in turn form into tornados.

Thunderstorms often form in the southern High Plains, and in the frontal areas of the Rocky Mountains in the Texas Panhandle, due to the air at ground level flowing upslope towards the upper regions of the terrain. These thunderstorms can often produce tornados if other tornado-producing conditions also exist.

Sometimes, tornados accompany hurricanes and tropical storms, which move over the land. Tornados usually form ahead and to the right of the path of the center of the storm as it comes ashore.

Here are the causes of tornados:

As is evident from the above, tornado conditions get created when different humidity levels and temperatures meet, leading to thunderstorms. In the U.S., wet, warm winds emanating from the Gulf of Mexico begin moving northwards in the spring and summer. These winds meet the dry, cold winds coming south from Canada. The area where these winds meet is known as the dryline. The dry winds from the north, which occur at higher altitudes of over 10,000 feet, begin piling up over the moist, warm winds from the Gulf, which are low. These southern winds try rising up, since they are warm, but are obstructed by the cold winds of the north. This collision results in the trapped, warm air rotating horizontally between the two masses of air. Simultaneously, the earth below gets heated by the sun, which warms more air, which then continues to try and rise upwards. Eventually, warm winds trying to rise up get so strong that they push upwards, penetrating the cold upper layer of air.

When this happens, the cold air starts sinking down, resulting in the warm wind whirling upward, spinning faster and faster, and forming a high column. When the upward moving winds are strong enough, it can go up to 10 miles in height, and even more, spinning at speeds measuring up to 100 mph. These spinning winds create powerful storm clouds, which occur at a height of 70,000 feet, often stretching 10 miles in width.

This stormy condition may remain intact for a number of hours, wherein the thunderclouds are referred to as supercells. These clouds can rain down an inch of water in just 10 minutes or pummel the earth with hailstones the size of baseballs. These supercells can gather into enormous clusters, which can form a line of about 100 miles in length, which then can form into mesocyclones. A mesocyclone is basically a vortex of air that measures about 2-10 km in diameter. When a mesocyclone occurs, it is thought to be one of the main factors for the formation of powerful tornados.