With less than 10 days to go before the Northeast monsoon draws to a close, the rainfall picture for most southern states looks largely normal, despite actual rainfall figures in four out of five sub-divisions in the south staying below the normal mark this season. The India Meteorological Department (IMD) had forecast in early October that the realised rainfall in South India would remain between 89 per cent and 111 per cent of the Long Period Average (LPA) in this period. The actual rainfall was close to the IMD forecast.
This year, meteorologists observed that the active rainfall period over the five sub-divisions — Tamil Nadu, Kerala, Coastal Andhra Pradesh, Rayalaseema and South Interior Karnataka, which benefit from the winter monsoon, lasted only till the first week of November, after which there was a long lull. Cyclone Ockhi, which originated in the Bay of Bengal, could have brought rain over larger areas of Kerala, Tamil Nadu and even Andhra Pradesh. However, the cyclone changed its course, denying any major contribution in rain quantum in these areas.
The major factor behind the lull, according to Met officials, was weak easterly winds blowing from over the Bay of Bengal, which left the east coast largely deficient in rain. Another reason was the absence of rainfall from moisture incursion due to fewer atmospheric systems originating in the Bay of Bengal. “Even the low pressure system, which succeeded cyclone Ockhi, skirted along the east coast, bringing very little rain over the coast for a brief period in November,” said a senior IMD official in Pune.
According to DS Pai, head climate prediction at IMD’s climate research division, few rainy days have been reported in December. He said, “So barring Tamil Nadu and coastal Andhra Pradesh, the monsoon needs to be seen as largely normal.”
In the final lap, with a system likely to develop over the Bay of Bengal close to the Comorin region, some rain has been forecast over Tamil Nadu and Kerala. “Some rainfall activity is expected over the two extreme southern states between December 27 and December 29. Most sub-divisions, as forecast, will receive close to normal rainfall by the end of the season,” said AK Srivastava, head, climate monitoring and analysis division.