Tropical cyclones

Storm surge, not wind, causes most tropical cyclone deaths, which is why mortality has fallen through evacuation and shelters rather than forecasting alone. Warm-core low-pressure systems derive energy from latent heat released as moist air condenses. Formation requires sea surface temperatures of roughly 26.5 °C at sufficient depth, Coriolis force (systems cannot form within about five degrees of the equator), weak vertical wind shear, mid-tropospheric humidity, and a pre-existing disturbance. Mature structure comprises an eye, an eyewall of strongest winds, and spiral rain bands. India Meteorological Department names north Indian Ocean systems.