Tamil Nadu Floods – 55cm of Rain in 7 Days According to NASA Satellite Data

Some areas of the southern Indian state of Tamil Nadu saw 55cm (21.7 inches) of rain fall between 09 and 16 November, 2015, according to the latest analysis from NASA and partners.

The heavy rain was caused by two slow moving tropical low pressure areas. One of the lows (System 97B) continued to linger along the south eastern Indian coast on 17 November, bringing heavy rain to parts of Tamil Nadu and at isolated places over south coastal Andhra Pradesh, India.

The heavy rainfall caused widespread flooding and the deaths of at least 70 people in Tamil Nadu. Parts of Sri Lanka have also been badly affected, especially northern areas. At least 3 people have died as a result of flooding there.

NASA Satellite Data and Analysis

NASA and partners around the world have been gathering rainfall data using an array of satellites.

NASA’s Integrated Multi-satellite Retrievals for GPM (IMERG) combines all data from 12 satellites into a global map of rainfall at half hourly intervals.

The rainfall accumulation analysis above was computed from data generated by IMERG during the past week from 09 to 16 November, 2015. An analysis of those data indicates that during the past week up to 550 mm (21.7 inches) of rain drenched India’s southeastern coast in the state of Tamil Nadu. Rainfall totals of over 200 mm (7.9 inches) were measured in large areas of southeastern India and northern Sri Lanka.

An analysis of rainfall data from Nov. 9 to 16, 2015 showed up to 550 mm (21.7 inches) of rain drenched India's southeastern coast in the state of Tamil Nadu. Over 200 mm (7.9 inches) fell in large areas of southeastern India and northern Sri Lanka. Credit Credits: NASA/JAXA/Hal Pierce
An analysis of rainfall data from Nov. 9 to 16, 2015 showed up to 550 mm (21.7 inches) of rain drenched India’s southeastern coast in the state of Tamil Nadu. Over 200 mm (7.9 inches) fell in large areas of southeastern India and northern Sri Lanka. Credits: NASA/JAXA/Hal Pierce

The Satellites Involved

The Integrated Multi-satellitE Retrievals for GPM (IMERG) creates a merged precipitation product from the GPM constellation of satellites.

These satellites include: DMSP (Defense Mapping Satellite Program) satellites from the U.S. Department of Defense, GCOM-W from the Japan Aerospace Exploration Agency (JAXA), Megha-Tropiques from the Centre National D’etudies Spatiales (CNES) and Indian Space Research Organization (ISRO), NOAA series from the National Oceanic and Atmospheric Administration (NOAA), Suomi-NPP from NOAA-NASA, and MetOps from the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).

All of the instruments (radiometers) onboard the constellation partners are inter-calibrated with information from the GPM Core Observatory’s GPM Microwave Imager (GMI) and Dual-frequency Precipitation Radar (DPR).

About the Tropical Low Pressure Areas

On 16 November at 1800 UTC (1 p.m. EST) System 97B was located just 55 nautical miles east of Chennai, India. It was centred near 13.2 degrees north latitude and 81.1 degrees east longitude.

On 17 November at 7:32 UTC (2:32 a.m. EST) the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard NASA-NOAA’s Suomi NPP satellite captured a visible image of System 97B. The storm stretched over southwestern Bay of Bengal near and the northern coast of Tamil Nadu and southern Andhra Pradesh coast.

The VIIRS image showed bands of thunderstorms wrapping from the northern quadrant into the southwestern quadrant. The Joint Typhoon Warning Center noted that computer models show that System 97B is expected to move in a northerly direction. Maximum sustained winds are estimated between 20 and 25 knots (23 to 28.7 mph/37 to 46.3 kph), and System 97B has a minimum central pressure near 1004 millibars.

The low pressure area continued to generate heavy rain in Tamil Nadu and at isolated places over south coastal Andhra Pradesh.