Chennai saw its worst rains in over 100 years on Dec 1-2, says NASA

The start of this month brought with it the heaviest rainfall Chennai had ever seen 24 hours since 1901, as per a report by NASA.

National Aeronautics and Space Administration, the reputed space agency, released an animated map yesterday, which provides satellite-based estimates of rainfall over southeastern India on December 1^st and 2nd, accumulating in 30-minute intervals. The floods came after a month of constant monsoon rains, which were already well above the normal range for Tamil Nadu.

In the rains and flood that has followed, at least 250 people have died, leaving hundreds severally injured, and thousands displaced.

The report from NASA said that the rainfall data come from the Integrated Multi-Satellite Retrievals for GPM (IMERG), which is a product of the Global Precipitation Measurement mission. As per Hal Pierce, a scientist on the GPM team at NASA's Goddard Space Flight Centre, the maximum rainfall totals were beyond 500 mm (20 inches) in an area that lies just off the southeastern coast.

"Meteorologists in India and abroad attributed the rains to a super-charged northeast monsoon. In the winter, prevailing winds blow from northeast to southwest across the country, which tends to have a drying effect in most places, particularly inland," the blog post said.

"But those northeasterly winds also blow over the warm waters of the Bay of Bengal, where they evaporate a great deal of moisture from the sea and dump it over southern and eastern India. Coastal eastern India receives 50 to 60 per cent of its yearly rainfall during this winter monsoon," it said.

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