Local Indian Ocean phenomenon may bring better rainfall despite El Nino

NEW DELHI: The dreaded El Nino, which often disrupts global weather patterns including the monsoon, is likely to be neutralised by a local phenomenon in the Indian Ocean, which can lead to good rainfall in the June-September season, top meteorologists said.
The phenomenon called Indian Ocean Dipole (IOD) refers to the temperature difference between the eastern and western parts of the water body. In the months ahead, western Indian Ocean is likely to be warmer than normal, a situation known as positive IOD.

“The negative impact of weak El Nino will be compensated by positive Indian Ocean Dipole. El Nino phenomenon is getting weak and IOD is moving from neutral to positive. This will help rains in the country. The monsoon would be near normal. We will soon come up with monsoon update,” said D S Pai, head of Long Range Forecast at the India Meteorological Department (IMD).



The IMD has maintained that this year’s monsoon would be close to normal, or about 96% of the 50-year average rainfall in the June-September season. Scientists at India’s official weather forecaster said there is no change in this forecast although private forecaster Skymet reiterated its prediction that rains would be below normal.

“A positive IOD, i.e. the warmer western Indian Ocean, brings good rains in the country. As the IOD is seen shifting towards positive phase from neutral, it is bound to cover up the deficit due to weaker El Nino,” Pai said.

The Australian weather office has also forecast positive IOD this summer. “The Indian Ocean Dipole (IOD) is currently neutral. However, models show a tendency towards positive IOD values during the forecast period, with five of six models suggesting a positive IOD event is likely,” it said.

The probability of El Nino developing this summer has also fallen from 70% to 50%, which is also a good development. Weather scientists say that in the past, in years of positive IOD, the monsoon progressed normally even when strong El Nino conditions prevailed.

El Nino refers to the warming of the equatorial Pacific, which weakens the flow of wind and consequently the monsoon system. In some other parts of the world, it leads to heavy rainfall but in India it weakens rain.

All six of the international climate models surveyed by the Australian weather office indicate that the IOD would be positive for June. For July, one model drops back to neutral, but the other five models forecast positive IOD values to persist through to at least the end of the outlook period (October),” its latest report said.