32 Days of Cyclone, Yet TN Short on Rains

Chennai:

There were 32 days of cylone and trough this year but it failed to garner in a wet spell in the state as Tamil Nadu faced 20 per cent deficit in annual rainfall on 2013.

Usuallly, the state’s average annual rainfall is 92mm but this year, it was short of 18 mm, according to Y E A Raj, deputy director general of meteorology, regional meteorological center (RMC), Chennai.

Raj blamed it on the cyclones which moved away faster to Andhra Pradesh resulting in may be a single wet spell. Interestingly, on an average the state has 12 to 13 days of cylone or trough but this year it had nearly 32 days of cylone. This could have huge rainfall potential. But then the tropical cyclones, which  are heat engines powered by the release of latent heat when water vapor condenses into liquid water, are hurt by wind shear.

The delicate balance of inflowing low-level winds and outflowing upper-level winds that ventilate the storm gets disrupted due to this phenomenon, says Raj.

He also said that the prevalent of positive southern oscillation, the atmospheric component of El Nino, a prolonged warming of sea surface temperature, may have been a reason for failure of North east monsoon.

Interestingly, the El Nino factor was neutral during the October-December period as such it did not benefit the north east monsoon. Raj said more studies have to be done in this regard.

Raj also said that it was the southwest monsoon that saved the city from a massive deficit. Interestingly, the city received more rainfall during the south west monsoon than the north east. “It is a rare phenomenon although it may have occurred twice or thrice. “This year the city received 60mm of south west monsoon while the north east monsoon was around 45mm. Normally it is the other way round. During the south west monsoon, the city receives 45mm of rains and during north-east it recieves 85mm of rains,” said Raj. Interestingly, it is being considered one of the five poorest north-east monsoon since 1969.

Interestingly, this time the annual rainfall in the city crossed beyond 100. And it was considered to be better than last year. The annual rainfall from 2004 has been good expect 2012 and 2013., he said.

T S Sridhar, additional chief secretary and commissioner of revenue administration (Disaster Management and Mitigation), who was also present on the occasion said that although the rainfall was better than last year but the state government would look into yield, and crop condition before declaring 2013 as year of drought. Interestingly, 2012 was considered a year of drought and the government gave away More than Rs 830 crore as aid to farmers.