Government of India
India Meteorological Department
Cyclone Warning Centre, Visakhapatnam
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  • Tropical Cyclones
    A tropical cyclone is a rotational low pressure system in tropics when the central pressure falls by 5 to 6 hPa from the surrounding and maximum sustained wind speed reaches 34 knots (about 62 kmph). It is a vast violent whirl of 150 to 800 km, spiraling around a centre and progressing along the surface of the sea at a rate of 300 to 500 km a day.The word cyclone has been derived from Greek word "cyclos" which means coiling of a snake. The word cyclone was coined by Heary Piddington who worked as a Rapporteur in Kolkata during British rule. The terms "hurricane" and "typhoon" are region specific names for a strong "tropical cyclone". Tropical cyclones are called Hurricanes over the Atlantic Ocean and Typhoons over the Pacific Ocean.

    Tropical Cyclone can be compared to a heat engine. The energy input is from warm water and humid air over tropical oceans. Release of heat is through condensation of water vapour to water droplets/rain. Only a small percentage (3%) of this released energy is converted into Kinetic energy to maintain cyclone circulation (windfield). A mature cyclone releases energy equivalent to that of 100 hydrogen bombs.

    Glimpses of devastation by some recent Cyclones that hit AP coast
    (Laila - May 2010)