Published on: August 30, 2021



What is in news : Hurricane Ida struck the coast of Louisiana, South USA as a powerful Category 4 storm



  • A hurricane is a large rotating storm with high speeds of wind that gust at least 74 mph that forms over warm waters in tropical areas.
  • Hurricanes begin as tropical disturbances in warm ocean waters with surface temperatures of at least 80 degrees Fahrenheit (26.5 degrees Celsius). Those low-pressure systems are fed by energy from warm seas.
  • A storm with wind speeds of 38 miles (61 km) an hour or less is classified as a tropical depression. It becomes a tropical storm—and is given a name, according to conventions determined by the World Meteorological Organization—when its sustained wind speeds top 39 miles (63 km) an hour.
  • Hurricanes are enormous heat engines that deliver energy on a staggering scale. They draw heat from warm, moist ocean air and release it through condensation of water vapor in thunderstorms.
  • Hurricanes spin around a low-pressure center known as the eye. Sinking air makes this 20- to 40-mile-wide (32- to 64-kilometer-wide) area notoriously calm. But the eye is surrounded by a circular “eye wall” that contains the storm’s strongest winds and rain.
  • Measurement
    • The size of Hurricane is mainly measured by the Saffir-Simpson scale – other scales are used in Asia Pacific and Australia.
    • The system divides storms into five categories:
    • Category 1: Winds 74 to 95 mph (Minor damage)
    • Category 2: Winds 96 to 110 mph (Extensive damage — Can uproot trees and break windows)
    • Category 3: Winds 111 to 129 mph (Devastating — Can break windows and doors)
    • Category 4: Winds 130 to 156 mph (Catastrophic damage — Can tear off roofs)
    • Category 5: Winds 157 mph or higher (The absolute worst and can level houses and destroy buildings)
  • Naming
    • Hurricanes are given names by the World Meteorological Organisation (WMO) so that they can be distinguished.
    • Each year, tropical storms are named in alphabetical order according to a list produced by the WMO.
    • That name stays with the storm if it develops into a hurricane.
    • The names can only be repeated after six years.