A US-based weather tracker has said that the seas off Kerala might just see a 'flare-up' in activity from May 24 to May 30 until when its forecasts are available.

This more or less aligns with the forecast timeline of May 30 (plus or minus four days) for the onset of South-West monsoon set by the India Met Department (IMD) earlier today.

MJO phase in?

The US Climate Prediction Centre said that a Madden-Julian Oscillation (MJO) wave may likely enter phases 2, 3 and 4 to boost the prospects of the onset dynamics of Kerala during this period.

The US National Centre for Environmental Prediction suggested that the onset could therefore happen in the upper band of the window projected by IMD.

The MJO wave is an eastward moving disturbance of clouds, windfall, rainfall and pressure that traverses the planet in the tropics and returns to its initial point starting point in 30 to 60 days.

This phase is called the 'wet phase' of the MJO; it also has a concurrent 'dry phase' that impacts the other half of the tropics, suppressing rainfall and aggravating drought.

Wave progression

The US tracker is of the view that a 'wet MJO ' would visit the Arabian Sea and the Bay of Bengal (phases 2, 3, 4) after having been initiated from somewhere on the African West Coast (phase 1).

According to it, an enhanced wave of rainfall could develop from the southern peninsular tip of India from around May 24, likely covering Kerala and South Tamil Nadu initially.

The disturbance is shown later to move north with heavier rain over North Kerala and adjoining Coastal Karnataka, with an eastern front being thrown open afresh off the Bengal/Odisha coasts.

Importantly, during this phase, the US tracker hints at the possibility of the rain wave heading out into the Arabian Sea north of Lakshadweep even as the rains hit the Goa-Konkan belt.

It remains to be seen if this would take the core of the monsoon out into the seas and away from the India coast in line with precedents often in the past, and something it can do best without.

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