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Monsoon 2021: ENSO favors good rains during the second half of season, IOD remains neutral

July 19, 2021 8:23 PM |

Southwest Monsoon 2021

ENSO neutral conditions continue to prevail across the entire stretch of the Pacific Ocean. Equatorial sea surface temperatures (SST’s) are near average across most parts of the ocean. ENSO neutral is expected during the Indian Summer Monsoon Rainfall (ISMR) season between June and September. There are over 65% chances for the La Nina potentially emerging through September – November season and lasting through the 2021-22 winters.

Nino indices for the last 4 weeks mostly remained neutral. The Oceanic Nino Index (ONI) based on SST’s departure from average in the Nino 3.4 region, is the principal measure for monitoring, assessing, and predicting ENSO. The current value of Nino 3.4, as on 12th July is 0.0 degrees Celsius.

Nino Indices

ENSO projections for the month of July depict a rising trend of the La Nina component and exceeds neutral towards the end of the monsoon season. This is a visible and significant change from the previous Nino plots. The pattern assures no threat of El Nino corrupting monsoon rains and rather the 2nd half of the season should perform better than the 1st two months of June and July. Pacific is likely to stay cool and therefore conducive for good ISMR.


Indian Ocean Dipole (IOD) continue to vary between 0 degrees and -0.5 degree Celsius. Its latest weekly value to 11th July was -0.46 degree as against the previous mark of -0.27 degree on 04th July. The IOD index has been below the -ve threshold for the last 6 weeks barring 04th July. Model indications do not suggest any significant drop hereafter but continue to remain marginally -ve.


The transitory index MJO (Madden Julian Oscillation) remains favorable, albeit with low amplitude, by remaining in phase 3&4. It may not trigger monsoon activity after 22nd July but the other 2 factors will push the monsoon rains over most parts.


The most crucial out of these 3 parameters is El Nino/La Nina and is showing promising signs. Monsoon can ride well over its own dynamics and cool Pacific. La Nina does not seem to be disappointing and the 2nd half of the season is reassuring better rains.

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