Weather models don’t invest much in fresh monsoon pulse

A moderately strong pulse of the Madden-Julian Oscillation (MJO) is currently located in the West Indian Ocean and the adjoining South Arabian Sea, which is expected to trigger fresh monsoon activity along the West Coast, though confined initially to the Northern reaches (Konkan, Goa and Mumbai).

This is because of the proximity of the region to a cyclonic circulation that has washed ashore from the North Bay of Bengal and is ensconced in the land-based monsoon trough from North-West India lying diagonally across the plains and Central India and its Eastern-end dipping into the waters of the Bay.

But global climate models do not expect the MJO wave to set off a buzz across the peninsula in the Bay since it is to forecast to weaken as it enters its waters. Unless low-pressure areas form, as they normally do after being nudged into it by the MJO, the monsoon may not be able to make a full-fledged revival.

Seas unusually silent

A fresh spurt of rains is seen around the two troughs - the offshore trough on the West Coast and the monsoon trough over land in the North. Only sustained lows with assured life for a few days over land can spread out the rain across time and space over large parts of the country. In their absence, the monsoon would be left to its own internal strength and inherent dynamics.

This lack of energy in the sea waters is not confined to the Arabian Sea or the Bay of Bengal. The Australian Bureau of Meteorology has noted that even the North Pacific Ocean (to our East) is witnessing below par activity, despite entering a climatologically favourable time of the year.

The North-West Pacific Ocean, which typically sees the highest annual tropical cyclone activity across the globe, has not seen a tropical storm since Nuri in the first half of June. There have been no typhoons (cyclones) in the region since Vongfong in mid-May.

No successor to Nisarga

Including the North-East Pacific and North Indian Ocean (Arabian Sea and the Bay), it is the first time since reliable satellite measurements began that no typhoons have been observed during a period spanning June 4-July 13. The last cyclone across this region was Nisarga in the Arabian Sea in early June.

Using energy (Accumulated Cyclone Energy–ACE) as a metric of tropical cyclone activity, the North Pacific Ocean has only seen about 20 per cent of its normal yearly activity so far this year. A weak tropical low has lately formed to the East of the Philippines but has small chance of developing into a cyclone.

Back home, the India Meteorological Department (IMD) has on Wednesday forecast fairly widespread to widespread rainfall over Konkan, Goa, Madhya Maharashtra and Gujarat during the next five days. Heavy to very heavy falls are likely over Konkan, Goa and Madhya Maharashtra till Thursday; at isolated places for the rest of Thursday; and over Gujarat State during the next three days.

Heavy rain forecast

Isolated extremely heavy falls are likely over Konkan, Goa and Madhya Maharashtra till Thursday and Gujarat on Thursday. Rainfall intensity may decrease significantly thereafter. Meanwhile, the strengthening trough over North India would bring fairly widespread rainfall with isolated heavy falls over the region during Thursday-Sunday.

Fairly widespread to widespread rainfall with isolated heavy to very heavy falls is likely over Madhya Pradesh and Vidarbha till Thursday. Moderate to severe thunderstorm and lightning has been warned over Madhya Pradesh, Bihar, plains of West Bengal, East Gujarat, Coastal Andhra Pradesh, Telangana, Rayalaseema, Tamil Nadu and Puducherry until Thursday morning.

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