Class 7 Science

Thunderstorm and Cyclone

The Indian Subcontinent lies in tropical zone. Due to this, the hot and humid climate of this place is ideal for thunderstorms.

When warm air moves up, it carries moisture along with it. When water reaches high altitude, it condenses to form ice.

Water, in the form of ice, falls rapidly towards the ground.

There is friction between upward moving air and downward moving water droplets. Friction results in thunder, accompanied with loud sound. This phenomenon is called thunderstorm.

Precautions During Thunderstorm

Thunderstorm to Cyclone

You may recall that when water absorbs heat, it turns into vapor. Opposite of this is also true. When vapor condenses into water, it releases heat.


The heat released during condensation of vapor warms up the air around it, and warm air rises up. This creates a region of low pressure in the surrounding. Cooler air from nearby areas move towards this center of low pressure to fill in the gap.

This starts a cycle of wind movement which results in formation of a system of low pressure surrounded by fast moving wind around it. The fast moving wind moves in many layers in the form of a spiral. This condition of weather is called cyclone.

The wind moving around a powerful center of low pressure is called cyclone. The direction of cyclone is anti-clockwise in northern hemisphere and clockwise in southern hemisphere.

The center of cyclone is called eye. The eye of cyclone is calm and clear. But there is a huge area of cloud around it that can be up to 150 km in diameter. The wind speed can be between 150 to 250 km per hour.

Devastation by Cyclone

Cyclones can be highly devastating. The high speed winds due to cyclone can result in ocean waves rising up to 12 meter high. When huge waves hit the coast, they result in heavy loss of life and property. The eastern coast of India is more prone to cyclone.

Precautions During Cyclone

Cyclone forecast and warning is very useful. Now-a-days, the progress in technology has enabled the meterological department to have plenty of data. This data is utilised to predict a cyclone well in advance. This has helped in reducing the loss of life and property to a great extent in recent years.

Fishermen, ships and oil barges get advanced warning so that people can be kept away from the sea. Ships move far away from the coast.

Cyclone shelters are made in areas which are prone to cyclone. Adequate facilities of food and medicine are ensured at these shelters.

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