Why Tamil nadu(INDIA) recieves extreme rainfall during winters as compared in summer?Explain.?

Answer 1

The period October to December is referred to as Northeast Monsoon season over peninsular India. Earlier this period was also referred to as "Post-Monsoon Season" or "Retreating southwest Monsoon Season".

Northeast Monsoon season is the major period of rainfall activity over south peninsula, particularly in the eastern half comprising of the meteorological subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamilnadu-Pondicherry. For Tamilnadu this is the main rainy season accounting for about 48% of the annual rainfall. Coastal districts of the State get nearly 60% of the annual rainfall and the interior districts get about 40-50% of the annual rainfall.

Though the principal rainy season for Interior Karnataka, Kerala and Lakshadweep is the Southwest Monsoon season, rainfall continues till December in these sub-divisions, the period October-December (Northeast Monsoon ) contributing about 20 % of the annual total.

The increase in rainfall activity over Andhra-Tamilnadu coasts which takes place sometime around middle of October is generally considered as the "setting in of Northeast Monsoon". Normal date of onset of the northeast monsoon is around 20 October with a deviation of about a week on either side.

The rainfall over south peninsula towards the end of southwest monsoon season is mainly in the interior districts and it generally occurs in the afternoon , evening or early part of the night. As the season advances the rainfall is mainly in the coastal districts with the interior districts getting less rain. It generally occurs during night and early morning hours . Maximum rainfall mostly occurs between 2100 and 0300 hrs IST. Along the east coast rainfall during late night and morning hours (2400 to 0900 hrs) is an usual feature of northeast monsoon. When there is a low, depression or cyclone close by the rainfall occurs throughout the day.

Northeast monsoon rains occur in spells of about 3 to 4 days duration. Spells exceeding 4 days are much less (20%). There are at times long spells of dry weather with little or no rain.