Hurricane Helen

Why in news?

• Recently 43 people died in 12 states in America due to Hurricane Helen.
• Due to this, about 1 crore 20 lakh people have been affected.
• Emergency has been declared in the US states of Florida, Georgia, North Carolina, South Carolina, Virginia and Alabama.

Hurricane:

• Hurricane is a type of cyclone.
• Its main feature is strong winds and heavy rainfall.
• It has different names depending on its place of origin.
  • Typhoon: In the China Sea and Pacific Ocean.
  • Hurricane: In the Caribbean Sea and Atlantic Ocean.
  • Tornado: In West Africa and the United States.
  • Willy-Willies: In northwestern Australia.
  • Tropical cyclone: ​​In the Indian Ocean region.

• The scientific name of all these types of storms is tropical cyclone.
• Tropical cyclones originate on the ocean surface between 8 degrees latitude and 15 degrees latitude in the northern and southern hemispheres.
• They originate in the western part of the oceans where the temperature is relatively higher than the eastern parts.
• Their direction is counter clockwise in the northern hemisphere and clockwise in the southern hemisphere.

• Factors of formation
  • Sustained sea temperature of 27°C or more is required
  • High humidity in the middle troposphere
  • Average wind speed is about 120 km/h
  • Presence of Coriolis force to start rotation
  • An initial low pressure area