Cyclone Jawad to bring heavy rain to Odisha, Bengal and A.P.
- A deep depression in the Bay of Bengal has intensified into cyclonic storm Jawad and is likely to make landfall near Odisha and Andhra Pradesh.
- Saudi Arabia has given the cyclone its name ‘Jawad’. The meaning ‘Jawad’ is liberal or merciful. The carries significance as this cyclonic storm will not be as severe as the previous ones.
How are cyclones formed?
- Cyclones are formed over the oceanic water in the tropical region.
- In this region, the sunlight is highest which results in warming of land and water surface.
- Due to warming of the surface, the warm moist air over the ocean rises upwards following which cool air rushes in to fill the void, they too get warm and rise — the cycle continues.
- Tropical cyclones are called by different names in different regions given below:
- Hurricane – Atlantic
- Typhoon – Western Pacific and the South China Sea
- Willy-Willies – Western Australia
- Cyclone – Indian Ocean
- They originate and intensify over warm tropical oceans
- A pre-existing weak low-pressure area or low-level-cyclonic circulation is a factor for its occurrence
What causes a tropical cyclone?
- Tropical cyclones, hurricanes or typhoons form when convection causes warm, moist air above the ocean to rise.
- They begin as a group of storms when the water gets as hot as 80 °F (27 °C) or hotter.
- The Coriolis effect made by the Earth’s rotation causes the winds to rotate. Warm air rises quickly.
- Tropical cyclones usually move westward in the tropics, and can later move north or south into the temperate zone.Tropical cyclones are powered by warm, humid ocean air.
- When they go onto land, they weaken. They die when they spend a long time over land or cool ocean water.
But what creates the spin?
- Wind always blows from high pressure to low pressure areas. High pressure areas are created in the cold region while low is created in the warm regions. Polar regions are high pressure areas as the amount of sunlight here is less than the tropical region.
- So, wind blows from polar regions to tropical regions.
- Then comes the Earth’s movement, which is west to east.
- The Earth’s rotation on its axis causes deflection of the wind (in the tropical region as the speed of spinning of Earth is higher compared to polar sides due to its spherical shape — blowing from both the polar regions.
- Wind coming from the Arctic is deflected to the right while Antarctic wind deflects to the left side.
- So, wind is already blowing in a direction.
- But when it reaches the warmer place, cool air starts getting attracted to the centre to fill the gap.
- So while moving to the centre, cool air keeps getting deflected resulting in circulation of wind movement — this process continues until the cyclone hits the land.
What are the 5 categories of tropical cyclones?
- Category one (tropical cyclone): A category one cyclone’s strongest winds are GALES with typical gusts over open flat land of 90-125kph.
- Category two (tropical cyclone): A category two cyclone’s strongest winds are DESTRUCTIVE winds with typical gusts over open flat land of 125-164kph.
- Category three (severe tropical cyclone): A category three cyclone’s strongest winds are VERY DESTRUCTIVE winds with typical gusts over open flat land of 165-224kph.
- Category four (severe tropical cyclone): A category four cyclone’s strongest winds are VERY DESTRUCTIVE winds with typical gusts over open flat land of 225-279kph.
- Category five (severe tropical cyclone): A category five cyclone’s strongest winds are VERY DESTRUCTIVE winds with typical gusts over open flat land of more than 280kph.
What happens when a cyclone hits the land?
- Cyclone dissipates when it hits the land as the warm water that rises and creates space for cool water is no longer available on land.
- Also, the moist air that rises up forms clouds leading to rains that accompany gusting winds during cyclones.