Is El Nino to blame for excessive rains in Tamil Nadu and Andhra Pradesh?

New Delhi: Does this year’s El Nino have anything to do with the floods in Andhra Pradesh and Tamil Nadu caused by excessive rainfall during the North East Monsoon?

After all, the rains in Tamil Nadu were excessive in 1997 too, which saw the strongest El Nino on record.

“During El Nino extreme rainfall occurs in Ecuador, Peru, and southwest US. The impact on winter rain is not as well documented, but in 1997, rainfall over Tamil Nadu was really high. Averaged over all El Nino, the winter monsoon is indeed higher than average,” said Wenju Cai, a principal research scientist specialising in El Nino modelling at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia’s national scientific agency.

Still, while the association of El Nino with drier southwest monsoon from June to September is well documented, not much research is available on the El Nino’s impact on winter rain or North East Monsoon season in India.

“There is no such relation regarding conversion, but generally it is seen that disturbances such as depression, low pressure systems and cyclones are more during post monsoon and pre-monsoon season. But during El Nino years, such systems in the Bay of Bengal have a typical feature that they move westward, while in other years they move eastward. This causes heavier rainfall in Tamil Nadu and other such coastal areas,” explained D.S. Pai, chief of long range forecasting division of India Meteorological Department (IMD).

“It is because of this typical feature that we had predicted above average rainfall this North East Monsoon season. Another problem is also that the heavy rainfall is concentrated in a few days,” Pai added.

What is clear, however, is that 2015 is seeing a very strong El Nino.

This October was the hottest October on record over the past 136 years, according to a latest report from the US National Oceanic and Atmospheric Administration (NOAA).

The World Meteorological Organization has said this year’s strong El Nino event, which has led to extreme weather patterns across the world, is expected to strengthen further by the end of the year.

“The El Nino is still growing, and is approaching the intensity of the 1997. It is possible to grow stronger than the 1997 (one),” said Cai.

The El Nino-Southern Oscillation is a weather phenomenon resulting from the interaction between the ocean and atmosphere in the east-central Equatorial Pacific and is characterized by warmer waters in the Eastern equatorial Pacific. This can disrupt weather patterns across the world ranging from droughts, floods to frequent cyclones.

India which usually faces drier than normal conditions in years with El Nino, faced a deficient monsoon this year after which eight states declared droughts.

“Severe droughts and devastating flooding being experienced throughout the tropics and sub-tropical zones bear the hallmarks of this El Niño, which is the strongest for more than 15 years,” said WMO secretary-general Michel Jarraud in a press release.

Peak three-month average surface water temperatures in the east-central tropical Pacific Ocean will be more than 2 degree Celsius above normal, which means this year’s El Nino event would be among the three strongest since 1950, according to WMO.

NOAA said that as strong El Nino conditions were in place, the October global sea surface temperature was 0.85°C above the 20th century average of 15.9°C which was the highest departure for October on record.

In the week ending 18 November, India Meteorological Department recorded rainfall of 329% more than normal in Chennai, 572% more than normal rainfall in Vellore and 656% more than normal rainfall in Kancheepuram as authorities struggled to cope with waterlogged cities.