The Australian Bureau of Meteorology (BoM), in its latest update, said that sea surface temperatures in the Central Pacific Ocean have warmed during the past fortnight, likely ending a weak La Nina phase.
Four of eight international climate models surveyed by the Bureau maintain La Nina values through March. By May, only one model still exceeds La Nina thresholds. For July, all eight are within the neutral (neither La Nina nor El Nino) range.
No ‘direct’ link
El Nino has been sought to be linked with dry or drought conditions in India from a ‘tele-connection’ with the warming pattern in Central and adjoining East Pacific. But no direct cause-effect relationship has been established.
Similarly, alter ego La Nina has been associated with the cooling of the Central and East Equatorial Pacific, at times translating into a normal or even excess monsoon for India.
Last year, around this time, the US National Oceanic and Atmospheric Administration had assessed the chance of an El Nino forming as about equal to the chance that neutral conditions would continue — both just shy of 50 per cent in terms of probability.
Falls short of target
Unlike two immediate past years, when the signal that a strong El Nino was developing was clear, most of the prediction tools had last year suggested ‘borderline’ conditions, making it a tough forecast.
What transpired was a normal monsoon for June and July, only to be followed by double-digit deficits during August and September. Thus, the season had ended with a rainfall of 95 per cent, less than what was actually forecast.
According to the India Met Department, during the period 1885-2007, there were 36 years of ‘warm’ El Nino and 25 years of ‘cold’ La Nina. During the 15 of the 35 El Nino years (42 per cent), the monsoon rainfall was below normal. During nine of the 25 La Nina years (36 per cent), the rainfall was above normal. This goes to show that there is no one to one correspondence between the seasonal warming/cooling of the Pacific and the Indian monsoon.
Positive outlook
‘Neutral’ conditions being forecast this year (2018) should mean that the monsoon is not swayed either way. But this is being contested by two international models, though surprising on the positive side.
The Busan, South Korea-based APEC Climate Centre is the most outspoken with an outlook of ‘enhanced probability for above normal precipitation’ for India during the first three monsoon months of June, July and August.
The UK Met Office has also come out with a similar outlook, though seemingly not as exuberant. These are early forecasts, and comes more than a month in advance of the first long-range forecast to be issued by the IMD.