Tropical and Extratropical Cyclone

Tropical Cyclone

• Tropical cyclones form over warm tropical oceans and intensify
• Tropical cyclones are intense storms that form over tropical areas and move to coastal areas, wreaking havoc with violent winds, torrential rainfall, and storm surges
• It is one of the worst natural disasters ever
• In the Indian Ocean, they are known as cyclones
• Hurricanes occur in the Atlantic Ocean
• Typhoons concern the Western Pacific and the South China Sea
• Western Australia’s willy-willies

Tropical Cyclone Favourable Conditions

• A large area of the sea surface with a temperature above 27° C
• The Coriolis force is present
• The vertical wind speed varies slightly
• A weak low-pressure area or low-level-cyclonic circulation that already exists
• Above the sea level system, there is a higher divergence
• The condensation process in the towering cumulonimbus clouds that surround the storm’s centre provides the energy that causes the storm to intensify
• The moisture supply is cut off after the storm reaches land, and the storm evaporates
• The place where a tropical storm makes landfall on the shore is known as the cyclone’s landfall
• Cyclones that cross the 20° N latitude line often recurve, making them more destructive
• The eye, a powerful spirally revolving wind around the centre of a mature tropical cyclone, is its defining feature
• The circulating system’s diameter can range from 150 to 250 kilometres
• The eye is a tranquil area with settling air
• The eyewall is a strong spiralling ascent of air to a greater height that reaches the tropopause around the eye
• In this region, the wind can reach up to 250 kilometres per hour
• There is a lot of rain here
• Rain bands may radiate from the eyewall, and cumulus and cumulonimbus clouds may migrate into the outer region
• The storm has a diameter of 600 to 1200 kilometres and forms over the Bay of Bengal, the Arabian Sea, and the Indian Ocean

Extratropical Cyclones

Formation of Extratropical Cyclone

• The front is initially immobile
• Warm air blows from the south and cold air from the north of the front in the northern hemisphere
• When the pressure drops along the front, warm air goes north and cold air moves south, causing an anticlockwise cyclonic circulation to form
• A well-developed extratropical cyclone with a warm front and a cold front results from the cyclonic circulation
• Warm air glides over cold air, causing precipitation as a series of clouds to form across the sky ahead of the warm front
• The cold front pushes the warm air up as it approaches from behind
• Cumulus clouds form along the cold front as a result
• The cold front advances quicker than the warm front and eventually overtakes it
• The cyclone evaporates as the warm air is totally lifted up and the front is occluded
• Wind circulation activities at the surface and aloft are intricately interrelated