North east monsoon 2018 outlook

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Most anticipated North East Monsoon (2018) finally made onset of November 1st, after playing hide and seek for the entire month of October. Despite the late onset, some could argue that October for south India was pretty good (especially Kerala and TamilNadu), with some places getting above normal rainfall (especially Nilgiris and Delta regions).

Following the onset, the southernmost districts of TamilNadu got lashed, recording first 200 mm daily R/F accumulation. Chennai and rest of TN got moderate rains after the official onset. 

After onset, a mini-break was observed, with the UAC system that formed around October 31st getting dissipated. However, another low pressure system (near SriLanka) will keep the NEM active during the Diwali season, with good rains primarily in South TamilNadu and Kerala. Places in North TamilNadu & Chennai, and south Interior Karnataka (e.g. Bangalore, which has not been getting good spells) will have to wait for another system, that will move in around November 14th from South-east Bay of Bengal, for some good rain show.

With MJO moving to Phase 2, looks like NEM season will be active up until 3rd week of November, with models predicting systems in Bay of Bengal that will move inland.

Long range outlook for NEM 2018:

Based on ENSO and IOD

Looking at a long range, ENSO and IOD are probably the main players that would control the NEM momentum. ENSO development is on track, with full onset expected late winter (around Feb 2019, when the atmosphere and ocean will be fully coupled to give ENSO like conditions). On the other hand IOD, is a bit tricky to predict. Meteorologists are saying that IOD has become + (crossing the SST threshold), but after mid November it will come back to a neutral phase. Generally speaking, the neutral phase is not conducive for NEM and is usually associated with below normal rains. However, is is possible that ENSO development may negate this and provide normal NEM 2018. It waits to be seen how NEM 2018 would finally pan out. 

For now, until about November 17th, the outlook is positive with energetic Bay pushing moisture to South India. 

My views (which are purely personal):

(a) Kerala will record normal rains during NEM 2018 (with south and central Kerala possibly getting above normal rains).

(b) South TamilNadu & delta regions will be probably the star of NEM 2018 season, and would possibly record above normal rains.

(c) North TamilNadu & Chennai may end up with slightly below average rains.

(d) The outlook for South Interior Karnataka doesn't look good and I am expecting below normal rains for S.I. Karnataka.

Lastly, if the IOD becomes neutral in later half of November (around Nov 22nd or so), then we could expect a longish break phase in NEM 2018, which may revive only in December 2018 with a shift in the convective cycle.

You can follow my twitter handle @SriGMFL

Disclaimer: The content given here are all personal views and the author will not be held responsible or held liable for any oversight or misinterpretation.


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