Context: As the rainfall over India in the month of october is 3% above Long Period Average (LPA) as a whole, there is the need to analyze different weather phenomenas that India witness during october.
Different weather features in the month of october:
- Withdrawal of Southwest Monsoon:
- The monsoons withdraw from the extreme north-west end of the country in September, from the peninsula by October and from the extreme south-eastern tip by December.
- In Punjab the south-west monsoons reach in the first week of July and withdraw from there in the second week of September.
- The south-west monsoons reach Coromandel coast in the first week of June and withdraw from there only in the middle of December.
- Unlike the sudden burst of the advancing monsoons, the withdrawal is rather gradual and takes about three months.
Source: JV IAS
- Northeast Monsoon rains:
- Direction of winds: While the south-west monsoon (summer monsoon) blows from sea to land after crossing the Indian Ocean, Arabian Sea, and the Bay of Bengal, the northeast monsoon (winter monsoon) blows from land to sea.
- The northeast monsoon does not have anything to do with northeast India.
- It derives its name from the direction in which it travels, from the northeast to the southwest.
- Causes rainfall over: Southern states, mainly Tamil Nadu, Kerala, Andhra Pradesh along with some parts of Telangana and Karnataka.
- Reason: It is caused mainly by the Western Disturbances, an eastward-moving rain-bearing wind system that originates beyond Afghanistan and Iran, picking up moisture from as far as the Mediterranean Sea, even the Atlantic Ocean.
- Cyclonic disturbances:
Over Arabian sea
Over Bay of Bengal
- Cyclonic activity is comparatively less intense in the Arabian sea.
- Arabian Sea cyclones are also relatively weak compared to those emerging in the Bay of Bengal.
- High-intensity severe cyclones originate frequently.
- Temperature difference: The low-pressure system of cyclones needs a continuous supply of heat.
- Bay of Bengal is warmer than the Arabian sea, it is able to provide the heat energy needed to sustain the low-pressure system.
- Sea surface temperatures and humidity: The Bay of Bengal receives higher rainfall and constant inflow of fresh water from the Ganga and Brahmaputra rivers.
- Absence of large landmass: Between the Pacific and the Bay, allows cyclonic winds to easily move into the Bay of Bengal.
- Cyclones from Pacific ocean: Low-pressure systems originating from the Pacific ocean also travel towards the left to the Bay of Bengal.
Source: Udaipur Kiran