Defying the earlier predictions, La Nina continues to dominate and is now forecast to last till Northern Hemisphere winters (Dec-Feb). Indian Ocean Dipole is unlikely to collapse before the fall of the year. Stationary MJO keeps the West Pacific a hot basin for tropical cyclones.
ENSO: The sea surface temperature (SST) anomaly for Nino 3.4 region, the principal measure for monitoring, assessing and predicting ENSO, continues to remain below the threshold of La Nina standards. The three-month running -mean SST departure in the Nino 3.4 region during June-August was -0.8 degree centigrade. The most recent ONI during July - September strengthened further to -0.9 degrees. The next triplet for Aug-Oct is also gauged at -0.8 deg to -0.9 deg.
La Nina conditions continue to prevail as the SST anomaly is colder than -0.5 degrees. Many of the atmospheric and oceanic conditions remain indicative of the continuation of La Nina till early next year. ENSO indices remain +ve: low-level easterly winds are topped by westerlies across the Pacific: Negative sub-surface temperatures are evident at the depth (100-150mtr) in the central and eastern Pacific Ocean. Overall, equatorial Pacific oceanic conditions are consistent with La Nina. Accordingly, the La Nina advisory remains in place.
IOD: The Indian Ocean Dipole has remained below the -ve IOD threshold (<= -0.4 deg) since June 2022.
The negative IOD is forecast to continue till the fall of the year, before decaying rapidly. The latest IOD index value, for the week ending 30th Oct, was -0.54 deg.
MJO: The Madden Julian Oscillation is still wandering over Western Pacific, with a fairly large amplitude. The basin was rather active, generating 2 tropical storms, Banyan and Nalgae, in quick succession, over the Philippines Sea. Both storms have since weakened. The magnitude of MJO is likely to drop as it shifts in the inner ring, after 09th Nov.
Near stagnant MJO and La Nina, the base state remains favourable for tropical storm formation over the South China Sea. However, remnants of cyclones are unlikely to travel to the Bay of Bengal. Northeast monsoon over the South Peninsula will proceed under the shadow of La Nina and -ve IOD.