With the stage now all set for the withdrawal of the four-month southwest monsoon season, Kerala can now heave a sigh of relief with September witnessing an above average performance of the monsoon. The monsoon deficit which was hovering around the 50% mark during the end of August, has now come down to 38% aided by a late surge, with hardly five days left before the formal ending of the season.
According to the India Meteorological Department (IMD), the conditions are becoming favourable for the withdrawal of the southwest monsoon from parts of Rajasthan by September 25 with dry weather prevailing over parts of southwest Rajasthan. For the withdrawal of the monsoon, rainfall activity over northwest India has to cease for five continuous days and there should be a reduction in moisture and anti-cyclonic activity up to 1.5 km.
Though withdrawal is likely to begin in a day, Kerala may witness a few more isolated intense spells triggered by the weather systems over the Bay of Bengal and due to the position of the monsoon trough. An extended forecast issued by the IMD hints at above average rainfall till the first week of October. This is expected to bring down the rainfall deficit by a couple of notches.
Normally, the withdrawal begins by September 17, but the back-to-back weather systems over the Bay of Bengal in September seem to have delayed the withdrawal for about 10 days. The season will draw to a close in Kerala with deficient rains. The latest global climate models, including the update by the Bureau of Meteorology, Australia, also suggest further strengthening of El Nino, a natural climate pattern borne out of unusually warm waters in the eastern Pacific, which is likely to persist until at least the end of February, and subsequent development of positive Indian Ocean Dipole (IOD), characterised by above normal sea surface temperature in the Arabian Sea.
In Idukki reservoir
When a positive IOD and El Nino occur together, the drying effect El Nino is expected to be suppressed by the positive IOD. This holds promise for the State in the forthcoming north-east monsoon season, which roughly provides an average of 500 mm rainfall to Kerala. The Idukki reservoir which accounts for the bulk of the hydel power production in the State, has only 36% water as of Sunday despite the late surge, whereas it had 81% water during the same day in the previous year.
