South-West Monsoon Onset (26 May, 2020) :

General Info :

* In general, the onset of South-West Monsoon over Kerala usually arrive on June 1st of every year. 

* Depending upon the onset of SW Monsoon over Kerala only, we (TN) will start having consistent SW Monsoon Rains. 

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* But, between June 2-4, a low-pressure area is expected to form over Arabian Sea and this will be moving towards North/ North-West and expected to make it's landfall is a depression / deep-depression state between June 8-10 in-between Oman and Gujarat. 

* The formation location and exact landfall location depends on 2 criteria's.

1. Support of Western Disturbances.

2. Date of the formation as MJO which will be arriving by 2nd week of June.

Below image is self explanatory. For further detailed understanding, read the description fully after the following image.

Cyclone formed by 1st week of June.?

* If the cyclone forms by 1st week of June, then this will impact the onset of SW Monsoon over Kerala. 

* What it will do is what Cyclone Amphan did for us (TN & AP) 10 days back, for which we are facing the heatwave till date. It will suck all the moisture from Kerala & Karnataka states.

Therefore, the onset of South-West monsoon will get delayed for a week atleast, to get the moisture back again over Kerala-Karnataka states.🌪️

* Only good thing is we will be getting some pull-effect rains with gusty winds once again over the ghat areas of TN (Coimbatore-Pollachi-Valparai-Kodai-Vagamon-Munnar-Manjolai-Nagerkoil-Kk).

Cyclone formation delayed and postponed to 2nd week of June.?

If this low pressure takes time to form and delayed for a week like Cyclone Amphan, the point to be noted is that MJO will arrive Indian Ocean by 2nd week of June, which will kick-start the SW Monsoon over Kerala by that time. But onset over Karnataka and North Kerala will be delayed. Also this MJO will be favour us (TN & AP), as Kerala will only be receiving some regular evening spells and MJO can be utilised for another Cyclone formation over the Bay of Bengal by June 2nd-3rd week.

Conclusion : 

We've to wait till the Low-Pressure over Arabian Sea is formed. We need to know when (date) and where (exact location) the formation is going to occur. Till that, it's a question mark for the onset of South-West Monsoon over Kerala on-time.