NEW DELHI: The La Nina climate pattern that was expected to develop around Aug and create conditions largely conducive for bountiful monsoon rains in Aug-Sept, is likely to be delayed by about a month. As per the latest forecast by US govt weather agencies released late Thursday, La Nina is now likely to set in around Sept, the last month of India’s rainy season.
Experts, however, do not expect a major setback for monsoon rainfall over the June-Sept season due to the projected delay in La Nina. The monsoon is currently 3% below normal over the country but the figure is expected to improve over the next two weeks.
The update by agencies affiliated to US’s National Oceanic and Atmospheric Administration (NOAA) gave a 70% probability of La Nina developing in the Aug-Sept-Oct period, generally taken to mean the month of Sept. The note said the probability of La Nina forming in Aug had reduced to 48%. In the forecast released last month , the probability of La Nina setting in around Aug was 65%.
In a La Nina event, surface waters in the east and central Pacific Ocean cool down below threshold temperatures, leading to associated changes in wind currents that impact weather around the world. The condition is a reverse of El Nino, where abnormal warming takes place. La Nina generally aids summer monsoon rainfall in India while El Nino often depresses it. In between the two states is a neutral or normal phase.
“The projected delay in La Nina shouldn’t be a cause of worry. The important thing from monsoon’s standpoint is whether the sea surface temperature anomaly in the region known as Nino 3.4 (in the Pacific) goes below zero. At the moment, it is slightly above zero but is likely to fall into the negative zone by Aug. When that happens, monsoon usually gets strengthened,” said M Rajeevan, veteran meteorologist and former secretary of the Union earth sciences ministry.