Chennai records around 50 to 60 percent of the rains during the Northeast Monsoon season of its annual rainfall. During the Northeast Monsoon season, northeasterly winds bring moisture from the Bay of Bengal which increases clouding over the region resulting in good rains over many parts of Peninsular India.
Sometimes, weather systems in the form of lows and depressions and even cyclones form over South Bay of Bengal resulting in heavy rains over Coastal Tamil Nadu including Chennai which has the case last year.
Usually, weather systems over the Bay track towards the west initially, further recurving towards the Northwest and thereafter towards the Northeast over Andhra and Odisha coast or Bangladesh.
However, last year, a couple of weather systems developed in the south Bay of Bengal and continued their westerly trend moving towards Tamil Nadu. Thus, heavy to extremely heavy rains occur over many parts of the state including Chennai.
This year, Northeast Monsoon has remained weak since the beginning and the weather systems developing in the Bay travelled in the northwest direction away from Tamil Nadu coast. These weather systems also restricted the northeasterly flow of winds which is essential for good rains over Tamil Nadu.
Thus, last year’s flooded Chennai has transformed into a dry and rain deficient Chennai this year. The residents of Chennai are not complaining as no one wants a repeat of the then Chennai rains.
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Please Note: Any information picked from here must be attributed to skymetweather.com