The northeast monsoon, which is on its last legs, is likely to withdraw from Tamil Nadu in a day or two.
Chennai is one of the 20 districts that had deficit rainfall this season. The city recorded a little over 100 cm of rainfall against the annual average of 140 cm.
Since October, the rainfall was short by over 30 per cent. Districts in the southern parts of the State however, benefited from the present spell of rain.
Addressing a seminar on the northeast monsoon 2012 organised by the Indian Meteorological Society, Y.E.A. Raj, deputy director general of meteorology, regional meteorological centre, said that the seasonal rainfall throughout last year had been deficit over the State, resulting in a shortfall of annual average rain by 23 per cent.
The deficiency in rain last year broke the rare phenomenon of eight consecutive years of unprecedented rainfall since 2004, according to the data available from 1871.
He also highlighted the variation in global climatic features — southern oscillations and the El Nino — that influenced the performance of the monsoon and long dry spells.
S.R. Ramanan, director of area cyclone warning centre spoke on the performance of the monsoon. The cyclonic systems that travelled in low latitudes and weak depressions resulted in reduction in rainfall. ‘Baupho’, a typhoon that struck Philippines took away moisture from the bay of Bengal and prevented much monsoon activity.
R. Venkatesan, a scientist from the National Institute of Ocean Technology, highlighted the role of the ocean buoy network in forecasting weather.
The data assimilated from nine buoys in the Bay of Bengal and nine more in the Arabian Sea is shared with the meteorological department.
“We do not share underwater parameters such as conductivity and temperature due to government regulations,” he said. The institute soon plans to introduce gliders, equipment that can travel up to any depth under the sea to acquire accurate data, he said.
R. Suresh, chairman of IMS, Chennai chapter, underlined the role of Doppler weather radar to track the movement of cyclone nilam and its significance in forecasting for aviation operations.