The Hindu Business Line : Monsoon draws to a close, rated ‘near normal’

Thiruvananthapuram, Oct. 1 The 2008 monsoon has ended with the country as a whole recording ‘near normal’ rainfall, according to an assessment by India Meteorological Department (IMD).

Rainfall for the season (June 1 to September 30) was 98 per cent of the long period average (LPA), the IMD said in its end-season report on Wednesday.

The spatial distribution was largely uniform with 30 meteorological sub-divisions recording normal rainfall. Punjab and Orissa were the only two to record excess rainfall, while as many as four ended up in the deficit category.

These are Nagaland-Manipur-Mizoram-Tripura, West Madhya Pradesh, Vidarbha and Kerala, with the last two being added fresh after rain figures were revised latest on September 24.

TEMPORAL VARIATION

The rainfall was marked by large temporal variation, being 27 per cent above normal in June but 17 per cent below in July. It was near normal during August and September with departure from normal being three per cent and one per cent respectively. The deficiency over peninsular India during June and July was compensated by the surplus rains during August and September.

The rapid progress of monsoon after the onset over Kerala on May 31 was matched only by the delay in its withdrawal from northwest India. The withdrawal from west Rajasthan commenced only on September 29 against the normal date of September 1.

The long range forecast for seasonal rainfall for the country as a whole and over different homogeneous regions, except northwest India, have been accurate. But the seasonal rainfall over northwest India and July rainfall for the country as a whole could not be predicted, the IMD said.

FORECAST FOR BAY

Meanwhile, the Climate Prediction Centre (CPC) of the US National Weather Services has warned that conditions are expected ‘to begin to become more favourable for tropical cyclogenesis (initiation of tropical activity, including cyclones)’ in the Bay of Bengal. The third week of the month (October 13 to 20) could be the most likely period for tropical development, an update from the CPC said on Wednesday. This would be brought about as a culmination of a series of events being carried forward right from October 1.

The CPC reasoned that the month of October is a period when the threat of tropical cyclone activity increases climatologically in the Bay. The continued propagation of the globe-trotting Madden-Julian Oscillation (MJO) wave of periodically enhanced convection and associated changes to the atmospheric circulations further increases this threat.

MJO WAVE

In fact, an MJO wave has been forecast to move in from West Africa to the west into the adjoining equatorial Indian Ocean during this period, say leading models tracking its movement.

In a recap of likely events panning out, the CPC too concurred that the first week of the month is likely to see an increased chance for above average rainfall for the West Indian Ocean attributed best to an incoming MJO wave and other ‘sub-seasonal coherent tropical variability’ (including, but not limited to monsoon transition from the southwest to the northeast).

The Roundy-Albany experimental model tracking cyclogenesis has maintained its watch for tropical activity in both the Bay and the Arabian Sea during this phase but stopped short of predicting development of full-blown cyclones.

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