The Hindu Business Line : El Nino trends may spare Indian monsoon for now

Thiruvananthapuram, July 2 The Australian Bureau of Meteorology’s (BoM) warning about a growing El Nino features an ‘escape’ clause for India monsoon, given the warming trends in tropical Pacific as on date.

On Wednesday, the BoM said more evidence of a developing El Nino event has emerged, and that computer forecasts show there’s very little chance of the development stalling or reversing.

The Pacific Ocean sea surface is currently significantly warmer than the long-term average across most of the tropical Pacific, especially central to eastern areas.

A large amount of the sub-surface water of the tropical Pacific is also warmer than the long-term average, particularly in the east.

ESCAPE OPTION

And here may lie the key to the ‘escape’ option for Indian monsoon. Warming trend towards east Pacific may not have as much impact on the monsoon as that around the central Pacific, which is closer to India.

This, along with signs of a weather-friendly positive Indian Ocean Dipole (IOD) event, may well be working behind the monsoon dynamics as evidenced in the ongoing surge along India’s west coast and eastern flanks.

A positive IOD event represents warming anomaly to southwest Indian Ocean (and adjoining Arabian Sea) relative to the east. The situation is reversed in the case of a negative IOD, which is bad for monsoon.

In its short-term forecast valid until July 12, the European Centre for Medium-Range Weather Forecasts, said the monsoon would continue to be in an active phase during the period.

Strong flows over the Arabian Sea and the Bay of Bengal are expected to consummate in the formation of low-pressure areas during this period.

BAY ‘LOW’

The Bay ‘low’ is seen moving west over land towards central India and merge with the counterpart system in the Arabian Sea, raining heavily all the way.

Entire central India, north peninsular India, western Maharashtra and adjoining west coast and Gujarat are projected to fall within the footprint of the westward progressing rain wave.

Indications are that an eastward-bound Madden-Julian Oscillation (MJO) wave may already be impacting the Indian monsoon as evidenced in the sudden spurt in heavy rainfall events over the west coast and elsewhere.

NORTHERN LIMIT

An India Meteorological Department (IMD) update on Thursday said the northern limit of the monsoon was locked along the previous day’s alignment along Udaipur, Jaipur, Pilani, Hissar and Ganganagar even as strong westerlies associated with a westerly trough interacted with available easterlies to cause widely separated heavy rainfall events over east and northeast India.

A warning valid for the next two days indicated the probability of heavy to very heavy rainfall events over the west coast and east India.

Heavy to very heavy rainfall is likely at a few places with isolated extremely heavy falls exceeding 25 cm in Assam, Meghalaya and Arunachal Pradesh.

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