are climatological phenomena that occur across the globe. They have certain characteristics that distinguish it from other atmospheric disturbances. These are:
- The foremost characteristic is that tropical cyclones are most violent, most awesome and most disastrous of all the atmospheric disturbances.
- The average speed is 120 kmph. Although it may vary from 32 kmph to 200 kmph or more. At times it reaches 400 kmph also.
- They have closed isobars. The pressure gradient is very sharp. More closely spaced isobars represents greater velocity of the storm and vice-versa. The pressure at the center is extremely low. The winds from the surrounding area are drawn towards this low-pressure core called the "eye" of the cyclone.
- Tropical cyclones develop over oceans and seas only. They are most violent and vigorous over water.
On landfall, their velocity decreases due to friction, and as the source of energy is cut off, they dissipate soon. Thus they affect the coastal areas only.
- The movement of tropical cyclone is affected by the prevailing wind system. Normally they move from east to west under the influence of trade winds.
- They are seasonal in nature and occur during a specific period of the year only.