The Indian monsoon is influenced by anomalies in the Niño 3.4 region.
“El Niño (La Niña) is a phenomenon in the equatorial Pacific Ocean characterized by a five consecutive 3-month running mean of sea surface temperature (SST) anomalies in the Niño 3.4 region that is above (below) the threshold of +0.5°C (-0.5°C).”
In the last 2 weeks the Niño 3.4 region has seen the SST anomaly drop from 1.1°C on April 25 to 0.6°C now. So it does look like that the current El Niño is dissipating and will very soon reach neutral conditions. That comes just in time for this year’s Indian monsoon (official season from 1st June to 30th September).
Both the government Indian Meteorological Department (IMD) and the private Skymet forecast an above average monsoon (about 10% above “normal”). However the IMD forecasts that the onset of the monsoon over the south-west coast will be delayed by about a week (June 6th -8th) but Skymet suggests that it will be on time and maybe even a day or two early (28th -30th May).
The Skymet prediction seems a little more credible to me. Right now a depression in the Bay of Bengal is bringing very heavy rain to the south-east tip of the peninsula and augurs well for the establishment of the monsoon. The formal “onset of the monsoon” is itself a complex matter. Technically the onset is declared when:
at least 60% of the 14 weather stations across Kerala and coastal Karnataka should record 2.5 mm rainfall or more for two consecutive days. ….. Simultaneously, the depth of the westerly winds should be up to 600 hPa (or 12000 ft high), from the equator to 10°N Latitude, and between Longitude 55°E and 80°E. The zonal wind speed over the area bounded by Latitude 5-10°N and Longitude 70-80°E should be around 25 to 35 kmph in the lower levels. The OLR value should also be less than 200 Wm-2 in the box confined by Latitude 5-10°N and Longitude 70-75°E.
While Skymet predicts monsoon conditions being established by end-May, IMD sees that about a week later. Possibly IMD have a smaller initial peak than Skymet.
Skymet’s Jatin Singh writes:
Skymet Weather believes that Monsoon will lash Kerala by the predicted dates between May 28 and 30. …..
…. There are high chances that the onset of Southwest Monsoon in mainland of India will coincide with El Niño reaching the threshold neutral stage. The in-built complex characteristics of Southwest Monsoon are also influenced by external oceanic-atmospheric phenomena like Indian Ocean Dipole (IOD) and Madden-Julian Oscillation (MJO). IOD will remain neutral for now and MJO will also traverse through the favorable zones of eastern Indian Ocean. Therefore, I think that the onset of Monsoon will not be hampered by El Niño, IOD or MJO.
Farmers, the government and industry are all looking for a good monsoon to kick-start the Indian economy into a steady period of growth. A “good monsoon” adds – directly and indirectly – about 2 percentage points to GDP. In the present climate where, in spite of the boost from lower oil prices, the Indian economy is dithering about taking off, a “monsoon factor” could be what is needed to secure the upward trajectory.