News: Hurricane Dorian made a landfall at Abacos Islands in the Bahamas.
- Hurricane Dorian is a Category 5 hurricane –the highest on the Saffir-Simpson scale. It had a wind speed of around 285 kilometres/hour at landfall.
- About Hurricanes:
- Hurricanes are name given to tropical cyclones occurring in the Atlantic Ocean. To qualify as a hurricane, a storm must have sustained winds of 74 mph or more.
- Categorization of Hurricanes: Hurricanes are categorized using a the Saffir-Simpson Hurricane Wind Scale which is a 1 to 5 rating based on a hurricane’s sustained wind speed:
- Category 1: Winds 74 to 95 mph (Minor damage)
- Category 2: Winds 96 to 110 mph (Extensive damage)
- Category 3: Winds 111 to 129 mph (Devastating)
- Category 4: Winds 130 to 156 mph (Catastrophic damage)
- Category 5: Winds 157 mph or higher (The absolute worst and can level houses and destroy buildings)
- Tropical cyclones are storms that originate and intensify over warm tropical oceans. They are intense low pressure areas with very strong winds circulating around it in anti-clockwise direction in the Northern Hemisphere and in clockwise direction in the Southern Hemisphere.
- The central calm region of the storm is called the “Eye“. The Eye is surrounded by Eye wall which is the region with heaviest precipitation and strongest winds
- Tropical Cyclones are known by different names in different regions:
- Cyclones in Indian Ocean
- Hurricanes in Atlantic
- Typhoons in Western Pacific in South China Sea
- Willy-Willies in Western Australia
- Necessary Conditions for development of a tropical cyclone and Formation:
- Continuous supply of abundant warm and moist air
- Sea temperature in lower latitudes should be around 27°C
- A distance from the Equator is necessary, so that it allows the Coriolis Effect to deflect winds blowing toward the low pressure centre. Tropical cyclones develop in inter-tropical convergence zone
- Pre-existence of weak tropical disturbances
- Presence of anticyclonic circulation at the height of 9 to 15km above the surface
- Low vertical wind shear between the surface and the upper troposphere. Vertical wind shear is the magnitude of wind change with height.