A cyclone or a hurricane forms over the seas and loses its strength immediately after landfall. Here are the reasons why:
Resistance – Cyclones always form over the sea, in open spaces and that’s where they gain strength. The terrain of the sea helps a storm gather its maximum strength whereas on land that strength is immediately cut off due too much resistance around. The increased friction over land acts as a somewhat obstacle, i.e. in the form of bushes, trees and houses and buildings, thus decreasing the speed of sustained winds. These sustained winds become weaker because of the dampening effect of larger roughness i.e. over land versus a relatively smooth ocean.
Moisture - A tropical cyclone over land will begin to weaken rapidly not just because of friction, but also because land lacks the moisture and heat sources that the oceans provide. This depletion of moisture and heat hurts the tropical cyclone's ability to produce thunderstorms near the storm’s center. Without this convection, the storm rapidly fills. However, recent studies done by ‘Nature’ showed that even over a swampy area a hurricane would weaken because of limited heat sources.
Sea temperatures – Adequate temperature is the most important factor in the formation and strength of a cyclone. Tropical cyclones derive their energy from the warm tropical oceans and do not form unless the sea-surface temperature is above 26.5°C. Also, sea temperatures by and large remain constant and vary very little, which helps in the genesis and the further growth of a cyclone. Whereas cyclones usually dissipate over land or over colder regions where the temperature profile varies widely and changes constantly. Land temperatures of 30⁰C and 20⁰C (in this case, in south India) at day and night, hinder the sustenance of a storm.
Strength – Not necessarily will a cyclone lose its intensity over land. There are times when a cyclone loses its strength over the seas itself. This happens because of proximity of the cyclone to the coast for a longer period, making the cyclone weak. The winds coming in from land are usually drier and thus affect the storm in
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