### Theory:

Anemometer:
Speed and direction of the wind play a vital role in the formation of storms, cyclones and thunderstorms. Therefore, it is so important to measure the wind speed and direction.
The wind speed can be measured with the help of an instrument called an anemometer.
Anemometer
The direction of the wind can be found using a weathercock or wind vane.
Weathercock
What is a cyclone?
Cyclone is a weather condition consisting of high-speed winds revolving around a very low-pressure area.
Cyclones are usually developed over the tropical seas like the Indian Ocean, the Bay of Bengal and the Arabian sea. The coastal areas of India are more vulnerable to cyclones.

Cyclone in the Bay of Bengal
Structure of a cyclone:
The centre of the cyclone is called an eye, which is a calm area having a diameter varying from $$10$$ to $$30\ km$$.
It consists of light winds alone, and no clouds will be present in this area. Around this area, a region of thick clouds at a size of about $$150\ km$$ is present. Also, the wind blows at high speed of about $$150$$$$–$$$$250$$ $$km$$$$/h$$ with a heavy rain. The wind speed gradually decreases away from this region.

A cyclone

Usually, a mass of air violently rotating in the atmosphere at the height of $$10$$ to $$15\ km$$ is said to be a cyclone which is large.
Formation of a cyclone:
We know that on heating, the water will change from the liquid to the vapour state.

Water absorbs heat from the atmosphere and converts it into vapour before the formation of clouds. Raindrops are formed when the water vapour changes to the liquid form. During this process, heat is released into the atmosphere and warms the surrounding air. This warm air rises and causes low  pressure, which makes the surrounding air move to the centre of the storm.

Schematic representation of a cyclone

Hence, this process is continued for some time and ends when there is a formation of high-speed winds revolving around a low-pressure system. This weather condition is termed a cyclone.
Factors required for cyclone formation:
• Wind speed,
• Wind direction,
• Temperature and
• Humidity
Humidity represents the amount of water vapour (moisture) present in the air or atmosphere.