Cyclone Amphan

IN NEWS:

• India is gearing up to deal with the potential impact of a super cyclonic named Amphan.

TROPICAL CYCLONES:

• A cyclone is a system of winds which rotate inwardly to an area of low atmospheric pressure. A tropical cyclone is one that originates in the tropical region.
• The ideal conditions for their formation are:
  • Warm sea surface, with temperatures > 27 °C
  • Presence of Coriolis force
  • Pre-existing low-pressure cyclonic circulation
  • Small differences in vertical wind speed
  • Upper air divergence
• They form only over warm water bodies because the energy that drives these storms comes from the condensation of the warm water.
• The winds rotate anti-clockwise in the northern hemisphere and clockwise in the southern hemisphere.
• "Amphan", pronounced as "Um-pun", means sky. The name was given by Thailand in 2004. 

CATEGORIZATION OF CYCLONES:

• The criteria followed by Meteorological Department of India (IMD) to classify the low-pressure systems in the Bay of Bengal and in the Arabian Sea as adopted by World Meteorological Organisation (WMO) are as under:

PRELIMS QUESTION:

Q. Which of the following conditions are essential for the formation of tropical cyclones:

1. Warm sea surface temperature
2. Presence of Coriolis force
3. Absence of vertical winds
4. Upper air convergence

Choose the correct answer from the codes given below:

1. 1 and 2 only
2. 1, 2 and 3 only
3. 1, 3 and 4 only
4. All of the above

Answer to Prelims question

Source: The Hindu