Brutal Heat Intensifies Across India; Generous Monsoon on the Way?

There are encouraging signs of a wetter-than-average monsoon in the cards for India this year--but until it arrives, millions of residents will have to deal with torrid pre-monsoon heat assaulting South and Southeast Asia this spring. More than 300 fatalities have been reported in the east-central Indian states of Odisha and Telangana. On May 1 and 2, at least 12 Indian locations broke or tied their all-time highest May temperatures. Accentuating the premature nature of this year’s heat, most of the prior records had been set during the last week of May. (Thanks to meteorologist Michael Theusner of Klimahaus for these statistics.) Extra weeks of heat stress are an ominous portent in this highly vulnerable nation. Some 2500 people were killed in 2015 by India’s second-deadliest pre-monsoonal heat wave on record, close behind 1998 (2541 deaths).

The pre-monsoon season is naturally a hot period in India: it’s the increasing contrast between land and sea that eventually brings the heat-quenching, life-giving summer monsoon. Yet even by pre-monsoonal standards, April was extraordinarily hot across the region, as reported by WU weather historian Christopher Burt. On April 24, it hit 48.5°C [119.3°F] in the east-central town of Titlagarh--the highest temperature ever reliably measured in India during April. “You can say there is an undeclared curfew in Titlagarh after 10 am. If you go out, you are either a very brave person or you are an outsider,” local Congress member Upendra Bag told the Hindustan Times. Titlagarh’s all-time high is 50.1°C (122.2°F) on June 3, 2003, and India’s hottest reliably measured temperature is 50.6°C (123.1°F) at Pachpadra on May 25, 1886.


Figure 1. Residents of New Delhi endure another day of sizzling heat on Monday, May 2, 2016. Monday hit a record 46°C (114.8°F) at Indira Gandhi International Airport and 44°C (111.2°F) at the city’s Safdarjung observatory. Image credit: Ramesh Sharma/India Today Group/Getty Images.


Figure 2.Departures from average in land-surface temperature across South and Southeast Asia for April 2016, as calculated from MODIS data (the Moderate Resolution Imaging Spectroradiometer aboard NASA’s Terra satellite). Some landscapes in Cambodia averaged more than 12°C (22°F) above normal for the month. Land-surface temperatures can vary significantly from air temperature. In this case, both air and land have been baking in relentless sunshine and record warmth. Image credit: NASA Earth Observatory.


Scorching in the Silicon Valley of India
One place where pre-monsoonal heat tends to be a bit less extreme is the highlands of southwest India’s Kerala state. The tech-oriented city of Bengaluru (Bangalore) is perched at near 900 meters (3000 feet), which helps keep a typical April day maxing out at no more than around 33°C (91°F). Yet on April 24, the city soared to 39.2°C (102.6°F), breaking the all-time record of 38.9°C for Bengaluru that extended all the way back to May 22, 1931. Schools in Kerala’s capital city of Thiruvananthapuram will be closed until at least May 20. In another Indian state, Bihar, the use of indoor cookstoves in rural areas has been banned between 9 am and 6 pm in response to heat- and drought-driven fires that burned 2500 houses and took 36 lives.

Some good news: outlook for the 2016 Indian monsoon
With El Niño now in its death throes, large-scale conditions are lining up favorably for above-average rains during the 2016 Indian monsoon. According to the India Meteorological Department (IMD), 71% of monsoon seasons that follow an El Niño produce near- or above-normal rainfall. The IMD’s initial outlook for the 2016 monsoon, issued on April 12, calls for 106% of long-term average rainfall for the nation as a whole, with a margin of error of plus or minus 5%. In probabilistic terms, the IMD is giving only 6% odds of below-average rains and a 64% chance of above-average rains.

Similar to the techniques used in many seasonal hurricane outlooks, the IMD employs a statistical forecast scheme for its April monsoon outlooks. The five variables are:

--SST gradient between North Atlantic and North Pacific (Dec + Jan)
--Equatorial South Indian Ocean SST (Feb)
--East Asia mean sea level pressure (Feb + Mar)
--Northwest Europe surface air temperature (Jan)
--Equatorial Pacific warm water volume (Feb + Mar)

Along with its statistical technique, the IMD is now collaborating with the Indian Institute of Tropical Meteorology and other agencies, including NOAA, on model-based monsoon prediction, using a research version of the NCEP Climate Forecast System (CFS). This coupled dynamical system paints an even brighter picture for the 2016 monsoon, projecting that it will produce 111% of India’s long-term national rainfall average (again plus or minus 5%). IMD will issue an updated outlook in June, including region-by-region forecasts. The private firm Skymet is also calling for an above-average summer monsoon, with 105% of average rainfall (plus or minus 4%).


Figure 3. Some parts of southern and eastern India that average 20 to 50 mm of rain (0.8” to 2.0”) from March 1 to May 3 (center) have received little or no rain this year (left), helping temperatures to soar well beyond typical pre-monsoon levels. Image credit: India Meteorological Department.


After two disappointing monsoons, hopes are high
As long as destructive flooding can be minimized, a generous summer monsoon would be a boon to India after the tepid outcome of the last two summer monsoons: 88% of average in 2014 and 86% of average in 2015. Far southeast India has its own monsoon in autumn, which is often boosted by El Niño and tamped down by La Niña--the opposite of the typical effects of these phenomena on India’s summer monsoon. As El Niño surged in strength last autumn, record rainfall caused devastating floods in Chennai and other parts of South India.

Thanks go to international weather records researcher Maximiliano Herrera for India heat statistics above. Herrera maintains a comprehensive list of extreme temperature records for every nation in the world on his website.

Bob Henson



Figure 4. People wade through a flooded street in Chennai, in the southern Indian state of Tamil Nadu, on Wednesday, December 2, 2015. Image credit: AP.