Monday, March 24, 2008

The entire regions of Tamil Nadu and Kerala have recieved rainfall amounts far exceeding thier normal amounts for the month of march. Manglore and Tvm have recieved their highest ever 24 hr. rain for March as well as the highest ever total for the month. There are a few more to add to the list with highest rainfall. Many of the stations in the 2 states have rain exceeding upto 1000% of their normal amounts.

As a result, the days have become cooler in the region, and the north-south divide in the temperature anomoly is seen in the map alongside. The overall average March temperature will make interesting reading, as the March temperature along the east coast is one of the parameters of the monsoon forecast model.

However, I notice a low, maybe insignificant, but showing over the regions of north Maharashtra/Gujarat today (IMD streamline shown). Should fizzle out in a day or two, as a significant low at the 500 hpa. level approaches the north-west areas of the country through Pakistan. Should bring fair amount of rain to northwest India and the hills of north India from the 26th.

Rains in Tamil Nadu/Kerala are bound to taper off with the advent of this W.D., but, some models in their GFS forecast another easterly wave approaching the south India coast by the 31st. March. , This should now be observed for the quantum of rain after the experiance of the previous wave.

This easterly repeat is due to the persistent positive SOI. The 30-day Southern Oscillation Index [SOI] to 15 March was +19, with contributing pressure anomalies of -0.2hPa at Darwin and +3.5 at Tahiti. The official monthly SOI for February was +21.

If the SOI remains at substantial positive levels, the rain patterns of south India will show much variations again in the coming months. Convective waves forming around the equator around the Indonesia regions will continue, as a result, and the easterly rain belts travel westwards.

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