The ocean temperatures along the central and equatorial Pacific are cooling off and ENSO neutral conditions are establishing all along the Nino regions in the Pacific Ocean. However, residual effect of the exiting El Nino on global temperatures still remains. Nino 3.4 region, the principal indicator of Oceanic Nino Index (ONI) continue to be reasonably warm. The index, once absolute neutral with zero-zero , regained the ocean warmth and stays positive neutral at +0.3°C. The SST anomalies all along the Nino region necessarily need to drop below zero for establishing the much awaited La Nina.
ENSO: The rate and extent of cooling, both at the surface and at depth has slowed during June. There is no broad agreement amongst the models about the timelines for La Nina. At best, 50% of these suggest that from August, SST’s are likely to remain at neutral ENSO levels and the rest half go in with the possibility of reaching La Nina level (below -0.5°C) in September. La Nina watch remains ‘on’ but that is no guarantee for La Nina development at some fixed timelines. As per Australian Bureau’s ENSO outlook, central tropical Pacific is likely to cool for at least the next two months.
There has been an irregular rise and fall in the anomalies across the equatorial Pacific Ocean. The most volatile being Nino 3.4 and Nino 1+2 region. Understandably, Nino 1+2 region being proximus to the coast is more vulnerable to churning and consequently the variations. However, Nino 3.4 region has mysteriously adopted an undulating pattern. For the last three weeks, the anomaly is holding steady between 0.3-0.4°C. It ranks amongst one of the longest episode of ENSO transition from El Nino to neutral and further to La Nina.
IOD: The IOD events are frequently observed to co-occur with the ENSO conditions in the tropical Pacific. Specifically, positive IOD events are typically accompanied by El Nino events, while negative IOD events are commonly linked to La Nina events. It remains a contentious issue whether ENSO conditions can drive climate anomalies that extend beyond the tropical Pacific, affecting global climate through atmosphere and ocean teleconnections. Some of the researchers have opined and considered ENSO as an important external forcing for the IOD sea surface temperature variability. Some earlier studies argued that the IOD might be an external mode and unlikely to get influenced by ENSO conditions. With such conflicting views, the IOD dynamics have remained open to debate.
The IOD is currently neutral. The latest weekly IOD index for the week ending 07thJuly 2024 was -0.19°C. The climate models suggest that the IOD will remain neutral until at least autumn beyond which IOD predictability is low. It may be construed that IOD may remain silent and could play only intrinsic role during monsoon.
MJO: The MJO is weak to moderate in strength. It is likely to remain weak for the next fortnight or so. The MJO pulse is likely to meander over eastern Indian Ocean with limited amplitude. It may further transition to the Maritime Continent in Phase 4 & 5. It may not help trigger any uptick in the weather activity over Indian seas.
After going through a vigorous phase, the southwest monsoon has lessened its fury. Yet, active monsoon conditions will prevail over the central parts of the country. Rains may even be dragged to Gujarat. The state may experience heavy spell of the monsoon covering most parts.