WHAT IS TROPICAL CYCLONE?

Tropical cyclones are violent storms that originate over oceans in tropical areas and move over to the costal areas. It brings large scale destruction caused by violent winds, very heavy rainfall and storm surges. The winds blow counter clockwise the Northern Hemisphere and clockwise in southern Hemisphere.

Terminology

It varies location to location . They are known as

• Cyclones in the Indian ocean
• Hurricanes in the Atlantic
• Typhoons in the Western Pacific and south China Sea and
• Willy - Willies in the Western Australia

Naming of Cyclones

• Adopting names for cyclones makes it easier for people to remember , as opposed to number and technical terms.
• Cyclones that form in every ocean basin across the world are named by the regional specialized meteorological centers and Tropical Cyclone warning Centers .
• There are six RCMCs in the world , including the India Meteorological Department and five TCWCs.
• The IMD is mandated to naming of cyclones as well as issuing advisories to 13 countries in the region on the development of cyclones and storms , namely Bangladesh, India, Maldives, Myanmar, Oman, Pakistan , Sri Lanka , Thailand , Iran, Qatar , Saudi Arabia, United Arab Emirates and and Yemen.

Conditions Favorable for the formation

• Large Sea Surface with Temperature higher than 27 degree celcius.
• Presence of Coriolis Force.
• Small variations in the vertical speed.
• Pre - existing weak low pressure area or low level cyclonic circulation.
• Upper divergence above the sea level system.

Characteristics

• The energy that intensifies the storm comes from the condensation process in the towering cumulonimbus clouds , surrounding the the centre of the storm.
• With continuous supply of moisture from the sea , the storm is further strengthened . The more time they spend over the seas the stronger they become.
• On reaching the land the moisture supply is cut off and the storm dissipates. The place where a tropical cyclone crosses the coast is called the Landfall of the cyclone.
• The cyclones which cross 20 degree North latitude generally , re- curved and they are more destructive.
• A mature tropical cyclone is characterized by the strong spirally circulating wind around the centre called eye. The diameter of the circulating system can vary between 150 and 250 Km. The eye is a region of calm with subsiding air.
• Around eye is the eye wall , where there is a strong spiraling ascent of air to greater height reaching the tropopause . The wind reaches maximum velocity in this region , reaching as high as 250Km per hour . Torrential rain occurs here.