Climatology/Cyclones

cyclone is a system of winds rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. around a low pressure center. There are two types of cyclones:

• Tropical Cyclone
• Temperate cyclone or Midlatitude or Extratropical Cyclones

Tropical Cyclone

A rotating system of clouds and thunderstorms that originated over tropical or sub-tropical areas.The major tropical-cyclone basins include the North Atlantic (including the Caribbean),Eastern Pacific, Western Pacific, North Indian Ocean, Southwest Indian Ocean, Southern Pacific and Australian region.It develop within 5 and 30 degrees of latitude.In the North Atlantic and Caribbean as well as the northeastern Pacific, they called hurricane. In the Northwest Pacific – the most active tropical-cyclone basin in the world is typhoons.but in the Indian Ocean and South Pacific they are called“tropical cyclones” or “cyclones.”

Temperate cyclone

The cyclonic storms that develop along frontal boundaries in the middle latitudes called “extratropical cyclones”or “midlatitude cyclones”. The polar front when the temperature difference between two air masses is large. These air masses blow past each other in opposite directions.Coriolis Effect deflects winds to the right in the Northern Hemisphere, causing the winds to strike the polar front at an angle.The temperate cyclones occur mostly in winter, late autumn and spring. They are generally associated with rainstorms and cloudy weather.

Characteristics of Temperate Cyclones

Size and Shape

• The temperate cyclones are asymmetrical and shaped like an inverted ‘V’.
• They stretch over 500 to 600 km.
• They may spread over 2500 km over North America (Polar Vortex).
• They have a height of 8 to 11 km.

Wind Velocity And Strength

• The wind strength is more in eastern and southern portions, more over North America compared to Europe.
• The wind velocity increases with the approach but decreases after the cyclone has passed.

Structure

• The north-western sector is the cold sector and the north-eastern sector is the warm sector.

Orientation And Movement

• Jet stream plays a major role in temperate cyclonogeneis.It also influence the path of temperate cyclones.