Southwest Monsoon 2020: Active MJO and strong IOD together can choke El Nino

April 10, 2020 4:24 AM |
Southwest Monsoon 2020

Southwest Monsoon 2020 is nearing the horizon. The wait is getting shorter with its likely appearance over the Bay Islands within the next 40 days or so. The trio of oceanic parameters, El Nino, IOD, and MJO keep resounding to remind us of their role and power. Sometimes they drown the hope even before the first drop of monsoon arrives while on few others raise morale and excitement for a promising season.

Monsoon 2019 is nearly unforgettable on records. Punishing El Nino ruined rains of the opening month June and MJO and IOD arrived later to the delight of farmers wrote a historic chapter. After all 'monsoon' has to live up to its reputation.

As per meteorologists, El Nino typically lasts for 9-12 months, IOD for 4-6 months and MJO comes in waves for few days and few times during the Southwest Monsoon season. The lesser-known and more unpredictable is the MJO (Madden Julian Oscillation). But it can have a dramatic impact in the tropics during monsoon season. While ENSO and IOD are stationary, the MJO is a transient disturbance of cloud, rainfall, wind, and pressure traversing nearly along the equator in the tropics. The average cycle of MJO could last from 30-60 days, while the El Nino and IOD may last for several seasons. MJO could visit multiple times over a region in a single season itself.

The MJO is an intraseasonal  oceanic index having two phases:  Active Phase( enhanced rainfall) and Suppressed Phase( least rainfall). For convenience, the meteorologists divide the planet into eight phases(1-8). At any point in time, two of these are active, another two are mild and the rest four are sleepy. The amplitude of MJO is another factor of concern and is rather tricky to predict. For the Indian Monsoon, MJO in phase 2 & 3 with an amplitude of 1 or more is considered favorable for enhancing rains, lasting for 7-10 days.


The MJO can produce rains similar to El Nino/ La Nina and IOD but its impact will appear in the weekly averages. This may get diluted in the monthly or seasonal projections. However, monitoring and assessing the strength of MJO for real-time impact remains a challenge.

The MJO has a vast empire to control and govern the atmospheric conditions. It can modify, retard or accelerate the timing of monsoon and its strength. It can alter the intensity and frequency of extreme events like drought, flood, 'break monsoon' and heatwave, etc.

The projection and forecast of MJO are done ranging from few days to few weeks. The farther the event, the lesser is the confidence and reliability also. The Bureau of Meteorology (BoM) generates the MJO forecast for 45 days. The current projections are indicative of the presence of MJO wave in the proximity of the Indian Ocean when the monsoon is around the corner to ingress Andaman and Nicobar Islands around mid- May 2020. Hopefully, the monsoon begins on the right foot for us.

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