Northeast Monsoon made onset over South India on October 28 and is likely to last till December. The Northeast Monsoon covers five subdivisions including Tamil Nadu, Kerala, Rayalaseema, South Interior Karnataka, and coastal Andhra Pradesh. Out of these subdivisions, Tamil Nadu benefits the most, while Kerala receives the highest rainfall amounts.
During the entire season of Northeast Monsoon, Tamil Nadu records 438 mm of rain on an average. Kerala records an average rainfall of 481 mm. South Interior Karnataka averages 210 mm, coastal Andhra Pradesh 327 mm, and Rayalaseema 219 mm.
Usually, the Northeast Monsoon sets in around October 20, but not before October 10. This year NE Monsoon was a little behind schedule. However, irrespective of the onset date, October rains are counted in the Northeast Monsoons season. As compared to the Southwest Monsoon, the variability in the quantum of rain is quite large.
Past records show that the onset date is not related to the performance of the Northeast Monsoon. The most delayed onset of the Northeast Monsoon on record has been November 2, in the years 1992 and 2000. The earliest onset in the last 25 years has been recorded as October 11, 2006.
The table below shows the onset dates and rainfall percentage departure (surplus/deficit), as recorded in the last 25 years:
During the El-Nino years, rainfall during Northeast Monsoon is usually normal or above normal. However, it is not a very well established fact. This year, the forecast for Northeast Monsoon is 111% of the LPA, with a probability of 88%. Tamil Nadu is expected to receive 112% of the LPA with a probability of 90%.
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