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The monsoon has made further progress over the eastern and north-western parts of the country even as it encountered fresh hurdle on the West Coast on its way to Gujarat.
On Tuesday, the seasonal rains entered Madhya Pradesh, Bihar, East Uttar Pradesh, Uttarakhand, Himachal Pradesh, and Jammu and Kashmir, the India Met Department said.
Trough weakens The pre-eminent monsoon feature in the form of the offshore trough has weakened yet again, bringing its progress along the West Coast to a brief halt.
The Met forecast indicates that the heavy to very heavy rainfall regime will be active for the next few days over the West Coast up to Konkan and Goa and the rest of North-West, East and North-East India.
Meanwhile, the Australian Bureau of Meteorology as well as the Application Laboratory of the Jamstec, the national forecast agency of Japan, suspect that the Indian Ocean may have already entered into a ‘negative dipole’ phase. A negative phase of the Indian Ocean Dipole (IOD) is a localised version of the El Nino-La Nina phenomena in the Pacific and has been found to modulate a concurrent Indian monsoon.
Negative IOD The IOD has positive and negative phases. The positive IOD signals to the warming of the western basin of the Indian Ocean and corresponding cooling of the eastern basin.
The positive IOD phase has boosted the Indian monsoon. The negative IOD phase, in which the warming shifts to the eastern basin of the Indian Ocean, has a ‘drag effect’ on the monsoon. It remains to be seen what a negative IOD can do to the monsoon this year.
The India Met has forecast it to be above normal thanks to the favourable vibes from a building La Nana conditions in the equatorial Pacific.
An outlook by India Met and Indian Institute for Tropical Meteorology had suggested earlier that positive IOD conditions are likely to prevail during the early part of the monsoon and negative during the latter part.
La Nina year There is a 74.1 per cent possibility for normal or above normal monsoon in an El Nino+1 year. So statistics favour a good monsoon year for 2016, the Met had said in its second long-range forecast.
In general, the monsoon is stronger than during normal during La Nina years, though there is no one-to-one association between the two.
However, there is stronger association between a La Nina and rainfall during the latter part of the monsoon, particularly with September rainfall.
During 1901-2015, there have been 24 La Nina years. Sixteen of them (67 per cent) returned above normal rainfall while seven (29 per cent) witnessed normal rainfall. But one year turned below normal.
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