El Nino could be weak and short-lived, says Australian Met

The Australian Bureau of Meteorology (BoM) has come out with updated on with two oceanic/climatic developments which could possibly bring good tidings for the ensuing Indian (Asian) monsoon. Firstly, it said on Wednesday morning that even of an El Nino develops in the Central and Equatorial Pacific, it would be short-lived and weak, which is mostly in line with the India Met Department (IMD) outlook.

Normal monsoon forecast

It may be recalled that the IMD had come out with its first long-range outlook for the 2019 South-West Monsoon only a day ago, and predicted a 'near-monsoon' (96 per cent of long-period average). It had argued its case based on a weakening El Nino, varying intense versions of which have often coincided with a poor monsoon. KJ Ramesh, Director-General, IMD, had explained its case to BusinessLine in detail.

The BoM said that while climate models forecast El Nino-like ocean temperatures during May, most models indicate a cooling through June to August, the first three months of the Indian monsoon. Only three of eight models are still forecasting El Nino-like warmth returning in September to November, which should be ideal for the North-East monsoon in India that starts in October. All these go to indicate that if an El Nino does develop, it is likely to be short-lived and weak, the Australian Bureau of Meteorology surmised.

El Nino alert retained

But it chose to retain its outlook at El Nino alert. This means the chance of El Nino developing in the coming months is approximately 70 per cent; around triple the normal likelihood. Although sea-surface temperatures in the tropical Pacific Ocean are still close to El Nino thresholds, the atmosphere is yet to show a consistent El Nino-like response.

The Southern Oscillation Index, which typically drops when an El Nino pressure pattern develops across the equatorial Pacific, remains neutral and trade winds are currently close to normal strength near the Equator. Meanwhile, the second piece of good news for India is that the Australian monsoonal conditions, which was active over North Australia last week, have completely dissipated.

This should clear the way for the orderly progress of the monsoon here since, in the past, lingering low-pressure areas/depressions Down Under in April/May have acted as a drag on the early phase of the Indian monsoon. El Nino typically brings drier than average conditions for Eastern Australia during June to November, and warmer days across South Australia.

Positive IOD phase

During March to May, the influence of El Nino tends to be weaker, but can bring drier conditions to the South of the country. The transition to the dry season is underway over northern Australia with reduced rainfall and lower relative humidity. Temperatures in the next few months are expected to be warmer than average. The Australian Bureau said that a relatively weak pulse of the weather-friendly Madden-Julian Oscillation (MJO) wave may develop over the Indian Ocean in the coming week.

It should help settle and further consolidate the seasonal thunderstorm activity over Sri Lanka and adjoining South Indian Peninsula, where the rains have been scanty up till now. In possibly a third good augury for the Indian monsoon, the Australian Bureau cited most climate models signalling that the Indian Ocean Dipole (IOD) likely remaining neutral for the remainder of March to May.

It could possibly turn into a positive IOD phase during June to November. A positive IOD typically means a healthy Indian monsoon since the West Indian Ocean warms up relative to the East and vice versa during a negative IOD (poor rainfall when it is the East warming up more).

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