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El Nino conditions in the tropical Pacific region are likely to strengthen, says the Australian Bureau of Meteorology, which closely tracks weather in the region.
Super typhoon Dolphin, which had helped drag in the monsoon over faraway and upstream Bay of Bengal, may also be bolstering the case of El Nino by default.
TYPHOON DOLPHIN
Dolphin strengthened bursts of westerly winds, which blow away from Asia, and helped warming of the ocean water below the surface, reinforcing the El Nino.
In the process, easterly trade winds in the southern hemisphere, which convert themselves as south-westerly monsoon winds, got weakened.
The net effect is that moisture, storminess and cloudiness get driven away from Asia and the larger monsoon region into equatorial and east Pacific (towards South America).
Warm anomalies remain across a large part of the northeast of the Pacific Basin, extending down the western coastline of both North and South America, the Bureau said.
TRADE WINDS LAG
This is one reason why monsoon watchers in India view El Nino conditions with circumspection even if there is no direct cause-effect relationship as proved in 1997.
In the latest update, the Bureau said trade winds have remained consistently weaker than average since the start of the year.
The Southern Oscillation Index (SOI), which indicates a regional pressure differential over the seas, has remained negative for several months indicating El Nino.
Values of between +7 and −7 generally signal neutral conditions. Sustained negative values below -7 indicate El Nino. The latest value is -16.5, the Bureau said.
SEA TEMPERATURES
Even on the sea surface temperature front, the values prevailing over some crucial stretches in the Pacific have been observed only on few occasions since 1980 — including in the strong El Nino years of 1982 and 1997.
All five closely tracked temperature indices exceeded +1 deg Celsius last week. This is the first time all weekly values have exceeded by this scale since February 1998.
Meanwhile, the Bureau said it did not find support from the upper levels of the atmosphere for the impending onset of southwest monsoon along the Kerala coast.
MJO WAVE
It was referring to the periodical Madden-Julian Oscillation (MJO) wave that travels periodically to the east across the Indian Ocean, which boosts convection and cloudiness at the ground level.
But the monsoon can prevail even without MJO, provided the onset pulse gathers the required strength and intensity on its own to drive itself north along the west coast of India.
Apart from triggering the onset of the monsoon, the MJO wave has also been responsible for setting up low-pressure areas, depressions, and even storms.
The Australian Met did not see an MJO moving over the Indian Ocean for at least the next two weeks.
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