The North Indian Ocean cyclone season is an annual event that occurs from April to December, with peak activity between May and November. This region, which includes the Bay of Bengal and the Arabian Sea, is prone to the formation of tropical cyclones that can cause significant damage to coastal areas and result in loss of life and property.
Overview
The North Indian Ocean is one of the most active basins for tropical cyclones in the world. On average, the region experiences four to six cyclones per year, with one to two of them being severe cyclonic storms. These cyclones are formed when the warm waters of the Indian Ocean evaporate and create a low-pressure area, which then rotates and intensifies due to the Coriolis force.
Factors Influencing Cyclone Formation
Several factors influence the formation of cyclones in the North Indian Ocean:
- Sea surface temperature: Cyclones require warm sea surface temperatures of at least 26.5°C to form and intensify.
- Vertical wind shear: Low vertical wind shear allows the cyclone to maintain its structure and intensity.
- Monsoon trough: The monsoon trough, a low-pressure area that extends from the Bay of Bengal to the Arabian Sea, provides favorable conditions for cyclone formation.
- Madden-Julian Oscillation (MJO): The MJO, an eastward-moving disturbance of clouds, rainfall, winds, and pressure, can enhance cyclone activity when it is in a favorable phase.
Classification of Cyclones
The India Meteorological Department (IMD) classifies tropical cyclones in the North Indian Ocean based on their maximum sustained surface wind speed:
- Low-pressure Area: Wind speed less than 31 km/h
- Depression: Wind speed between 31 and 49 km/h
- Deep Depression: Wind speed between 50 and 61 km/h
- Cyclonic Storm: Wind speed between 62 and 88 km/h
- Severe Cyclonic Storm: Wind speed between 89 and 117 km/h
- Very Severe Cyclonic Storm: Wind speed between 118 and 166 km/h
- Extremely Severe Cyclonic Storm: Wind speed between 167 and 221 km/h
- Super Cyclonic Storm: Wind speed above 222 km/h