Oceanic parameters like La Nina, IOD, and MJO are approaching a crucial phase. These indices play a decisive role in the overall performance of the southwest monsoon. El Nino/La Nina will soon cross the spring barrier and the Indian Ocean Dipole projection will become more reliable in May. Madden Julian Oscillation is a transient wave of clouds and rains, moving in the equatorial belt, accentuating convection under its area of influence.
ENSO: La Nina continues to be active, despite showing signs of weakening earlier in February. All the 4 Nino indices retain the -ve values below the threshold mark. The entire equatorial Pacific Ocean remains cooler than average. However, the trade winds which had strengthened earlier, to stall the decline of La Nina, have eased in speed. This may lead to a gradual warming of the Eastern Pacific first and then rolling over to the central parts, hosting Oceanic Nino Index (ONI).
Sea Surface Temperature is not having a uniform distribution across the equatorial Pacific Ocean. Therefore, a clear verdict on the continuation or cessation of La Nina is not feasible at this stage. However, even the retreating La Nina conditions will keep influencing global weather and climate, including monsoon for the Indian Sub-Continent.
IOD: Indian Ocean Dipole is neutral. The latest IOD index value for the week ending 10th April was -0.04°C. Most of the models project IOD to reach a negative threshold (-0.4°C) by June and slide further as the monsoon progresses. Model output at this point is to be taken with caution, as accuracy is low and generally becomes reliable in May. Over a span of 10 years, on average, IOD is +ve and -ve for 2 years each and remains neutral for the rest of the years. Before the onset of monsoon, invariably a heat pocket develops over eastern and southeastern parts of the Arabian Sea. This builds up the temperature differential and accentuates the monsoon surge. It gets filled up quickly after the onset of monsoon over the mainland.
MJO: Madden Julian Oscillation is weak and rather far away from the Indian Ocean (Phase 1,2,3). Model indications indicate that MJO will be indiscernible and poor in amplitude and therefore will not have any influence on tropical weather for the next fortnight or so. The location and intensity of MJO will become significant from May onward. There are instances when the favorable presence of MJO becomes instrumental for the early onset of monsoon over the Andaman Sea and Bay of Bengal. Presently, MJO is not going to support any convective activity over the Indian Seas, till 25th April.
Skymet has released the Monsoon 2022 forecast and assessed it to be normal at 98% rainfall of Long Period Average of 880.6mm. La Nina and IOD are not likely to be in sync. Accordingly, the monsoon though will be normal but will have a tight rope walk, through its 4-month-long journey from June to September. 2nd half of the season appears to be at some risk of inadequate rains.
