Barring Northwest India, the remaining three regions are facing rainfall deficiency as El Nino gathers strength and Indian Ocean Dipole (IOD) climate pattern index remains neutral. Madden Julian Oscillation (MJO) is seen to contribute to El Nino as it gains strength in the coming weeks.

MJO, a global scale feature of the tropical atmosphere, is also fluctuating in the tropical weather on weekly to monthly time scale. MJO effects are most evident over the Indian Ocean and Western Pacific Ocean.

While precipitation remains 20% less than the benchmark long period average (LPA) in East and Northeast India, the South peninsula and central India have seen 13% and 2% below normal rains since the beginning of the monsoon season in June. With this the rainfall across the country stands at 579.3 mm, 7% lower than what is normal for this period.

“Seasonal rainfall has succumbed to the impact of El Nino in the core monsoon month of August… The month of August has witnessed an unprecedented shortfall of nearly 40% rainfall so far. Marginal recovery is likely in the 3rd week but still not adequate to offset regional deficiencies,” Skymet said in its latest bulletin on El Nino.

El Nino has significant impact on global weather. Equatorial sea surface temperatures (SSTs) in the Pacific transitioned from below average to above average in January this year and since March, positive SST anomalies in the eastern Pacific Ocean expanded westward. These anomalies have strengthened over the last six months and the Pacific Ocean has responded quite early to the call of El Nino. Now the atmosphere is aligned to evolve perfect ENSO (El Nino southern oscillation).

For the El Nino event, the surface temperature anomalies in the Nino region need to breach the threshold mark of +0.5°C for longer duration. The steeper the rise, the stronger the El Nino. “Given the recent trend in the Pacific, the degree of confidence for a stronger El Nino event looks imminent during fall of the year. The anomaly may reach or exceed 1.5°C from the seasonal average in the Nino 3.4 region,” said Skymet president GP Sharma.

The US National Oceanic and Atmospheric Administration recently announced that the chances of an El Nino event this season has increased to 95% and with greater confidence in a “strong” El Nino event.

Meanwhile, the IOD climate pattern index is currently neutral. The IOD index has been sliding for the last few weeks but unable to breach the threshold mark.

“The IOD index is still ricketing and not good enough to take on the blues of El Nino. The climate models suggest a positive IOD event in the coming weeks, but the mismatch between the model output and the actual value is discernible,” Sharma said. “IOD needs to be rising steeply to break the shackles of Pacific warming.”

“The MJO is in the Western Hemisphere with a slight increase in amplitude. Few models are forecasting moderately strong MJO pulse over the Pacific Ocean in the coming weeks. This may possibly assist further strengthening of El Nino conditions,”

It influences largely typhoon activity over the Western Pacific and hurricane development in the Eastern Pacific and the formation of monsoon systems over the Indian Seas. It can steer the monsoon pattern to bring intraseasonal variability.

Updated: 21 Aug 2023, 10:29 PM IST