ENSO, IOD Both Neutral; MJO Passive Too
The relationship between ENSO and the Indian monsoon is not as simple and straightforward as you’d normally think. El Niño does not always mean drought, and La Niña may not bring bountiful monsoon rainfall every time. ENSO-neutral by itself has all shades of seasonal rainfall: normal, below normal, and above normal.
ENSO-neutral in 1979 led to drought, with seasonal rainfall at 81% of LPA. These variations happen regardless of the strength of Pacific conditions.
The monsoon is a highly energetic circulation and has the potential to drive on its own. Yet, other weather and climate influences also help to propel the Indian monsoon circulation, and they can be enhanced regardless of ENSO. One of these factors is the Himalayan/Eurasian snow extent. Research suggests that less snow cover means a warmer Indian sub-continent, which can help to intensify the large-scale circulation and bring more rains to the region.
The Intertropical Convergence Zone (ITCZ) is another escalating factor, largely influencing seasonal rainfall. The position of the ITCZ is crucial for the Indian monsoon. During the summer months, the ITCZ migrates north and oscillates as well, north and south during the season, dragging the rainfall belt along with it. It is also closely linked with the monsoon trough, which is a region of low pressure that drives the monsoon circulation.
ENSO: Atmospheric and oceanic indicators continue to show ENSO-neutral conditions. The equatorial Southern Oscillation Index for May 2025 was 0.4, falling within the ENSO-neutral range. The most recent weekly average of the Nino 3.4 index, as on 02nd June, was -0.1°C. The quarterly ONI for Mar-Apr-May is assessed at -0.04°C. The monthly average of the Nino 3.4 index for May 2025 was -0.07°C. Therefore, the latest seasonal, monthly, and weekly values of the Nino 3.4 index suggest that the tropical Pacific has been experiencing neutral conditions for a fairly long time. The atmospheric arm (SOI) is firmly aligned with the oceanic component (Nino 3.4). Therefore, together, these observed conditions in the coupled ocean–atmosphere system indicate ENSO-neutral conditions in the equatorial Pacific.
All four Nino indices across the Central and Eastern Equatorial Pacific Ocean have remained within the neutral domain for the last 10 weeks. Yes, Nino 1+2 has been fluctuating far and below the threshold mark. That variation is quite understandable due to proximity to the coastline.
IOD: The Indian Ocean Dipole is an inherent mode of climate variability over the Indian Ocean, independent of El Niño/La Niña phenomena. Positive and negative IOD events generally both occur in boreal summer and autumn (from June through November). Positive (negative) events are identified when the three-month running mean DMI is +0.4°C or above (-0.4°C or below) for at least three consecutive months between June and November.
The IOD has turned zero-zero after staying in the positive-neutral domain for the last 10 weeks. The Bureau’s model predicts a neutral state of the IOD until at least July, after which it forecasts a shift towards negative IOD. Skill for IOD forecasts made at this time of the year has been historically low beyond 1–2 months ahead.
MJO: Latest observations continue to point to disorganized MJO activity, with the RMM signal still meandering in and out of the unit circle over Phases 4 & 5 during the past week. The recent tendency towards a positive signal over the Western Pacific may tide over the stalled monsoon and restore convective activity over the Indian Seas. Consistent with dynamical model guidance, the forecast suggests reorganizing MJO in June. During the next one week, the pulse is expected to propagate eastward over the Western Pacific and Western Hemisphere at a higher amplitude. Sleeping MJO may now become consistent to offer better support to the tropical convection over Indian Seas.
In the absence of any oceanic support, the early and robust onset of the monsoon got stalled within no time. Both the western and eastern arms of the monsoon struggled to move ahead. Likely development of a monsoon system in the Bay of Bengal may break the jinx of slow travel and take the monsoon surge deep inland on either side of the coastline.
