Northeast Monsoon is the lifeline of Tamil Nadu and results in 35 percent of its annual rains. It covers five subdivisions including Tamil Nadu, Kerala, Coastal Andhra Pradesh, Rayalaseema and South Interior Karnataka. Its normal onset date is October 20. In fact, Northeast Monsoon enters after the reversal of wind pattern takes place, i.e. when southwesterly winds change to south-easterlies.
The normal date for setting in of the easterlies over Peninsular India is October 14, but the onset of Northeast Monsoon takes place around October 20. There is no date of onset for each region unlike the Southwest Monsoon, here once Northeast Monsoon makes an onset, it covers the entire Peninsular India.
Northeast Monsoon is known to have a lot of fluctuations. In fact, in the year 2016, Northeast Monsoon was 62 percent deficit while in 2015, it saw a surplus of 52 percent.
Talking about this year, This time, October was bountiful with South Interior Karnataka witnessing a surplus of 83 percent, followed by Kerala at 55 percent, Coastal Andhra Pradesh at 32 percent, Rayalaseema 30 percent and Tamil Nadu 27 percent.
November, on the other hand was disappointing with all the regions being deficient. The deficiency was the highest for Coastal Andhra Pradesh at -83 percent, followed by Rayalaseema -70 percent, South Interior Karnataka -38 percent, Tamil Nadu -30 percent and Kerala -22 percent.
December was much better with all regions seeing normal and above normal rains with the highest beneficiary being Rayalaseema at 53 percent, followed by 44 percent for South Interior Karnataka, 13 percent for Tamil Nadu, 3 percent for Kerala and -5 percent for Coastal Andhra Pradesh.
Overall, Northeast Monsoon has had a decent performance this time with the season ending on December 31. In some parts the performance has been above normal which includes South Interior Karnataka at 53 percent and Kerala at 27 percent, and the others have seen within normal range performances with Tamil Nadu and Rayalaseema ending the season at 1 percent each, and Coastal Andhra Pradesh at -11 percent.
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Please Note: Any information picked from here must be attributed to skymetweather.com