Cyclone Phethai to make landfall in Andhra Pradesh today

Cyclone Phethai to make landfall in Andhra Pradesh today

News:

Cyclone Phethai heading northward from the Bay of Bengal makes landfall in Andhra Pradesh

Facts:

• Cyclonic storm Phethai has made a landfall at Katrenikona in Andhra Pradesh’s East Godavari district.
• This is the third cyclone to hit the state this year after Cyclone Daye and Cyclone Titli
• Phethai is relatively less severe when compared to Titli that ravaged Srikakulam district in north coastal Andhra region

What is a cyclone?

• A “Cyclone” is an intense vortex or a whirl in the atmosphere with very strong winds circulating around it in anti-clockwise direction in the Northern Hemisphere and in clockwise direction in the Southern Hemisphere.

Tropical Cyclones:

• It is a system of low pressure occurring in tropical latitudes
• The differential heating over land and sea probably causes a small area of low atmospheric pressure to develop.
• Tropical cyclone activity is at its maximum in late summer and early autumn
• Tropical cyclones follow a parabolic path; their axis being parallel to the isobars.

Characteristics:

• Cyclones are intense low pressure areas – from the centre of which pressure increases outwards
• The amount of the pressure drop in the centre and the rate at which it increases outwards gives the intensity of the cyclones and the strength of winds.
• Cyclones are of two types: Temperate cyclone and Tropical cyclone. Tropical Cyclones are among the most destructive phenomena.

Necessary Conditions for development of a tropical cyclone and Formation:

• Continuous supply of abundant warm and moist air
• Sea temperature in lower latitudes should be around 27°C
• A distance from the Equator is necessary, so that it allows the Coriolis effect to deflect winds blowing toward the low pressure centre. They develop in inter-tropical convergence zone
• Pre-existence of weak tropical disturbances
• Presence of anticyclonic circulation at the height of 9 to 15km above the surface
• Low vertical wind shear between the surface and the upper troposphere. Vertical wind shear is the magnitude of wind change with height.