India Meteorological Department (IMD) has joined the vigil for what likely is a brewing ‘low’ in North Bay of Bengal later this week (June 4, Thursday).
The European Centre for Medium-Range Weather Forecasts (ECMWF) is already on record with its projection of a churn in North Bay but had little found little support from peer models.
WESTERLY TRIGGER
The ECMWF says that the system would be triggered as an itinerant westerly trough dips into the Head Bay.
The causative western disturbance moved into Jammu and Kashmir on Sunday with a trough in the upper levels of the atmosphere.
The entourage is predicted to get a move to east India during the course of the week.
The ECMWF sees the system locking itself to a slot over the Head Bay and staying there for a while.
Proximity to land grants it hardly any elbowroom to move around the waters to intensify.
But the system may beat odds to intensify before making a landfall, yet again, over West Bengal.
This is the track chosen by predecessor Cyclone Aila as it crossed land earlier last week.
LIKELY STORM
Given that there is no much room for lateral movement, what could likely fuel the growth of the Bay system is its staying power over waters (June 4 to a likely landfall date of June 9 according to ECMWF) and the low vertical wind shear from a still poorly developed monsoon.
Early monsoon and end monsoon stages offer themselves as windows of opportunities for cyclone formation thanks to low vertical wind shear.
High wind shear during peak monsoon lops off towering heads of building storms and prevents cyclogenesis.
ECMWF projections also indicate the monsoon getting a leg-up over the southeast coast as also parts of east-central India (parts of interior Orissa, Andhra Pradesh and Maharashtra) as the Bay system gets anchored.
The IMD update on Sunday also noted that there has been no progress in the monsoon from its May-25 bearing.
Numerical models suggest that further advance is not likely during next three to four days.
WEST COAST RAINS
The activity is likely to remain subdued over south peninsula except west coast where rainfall activity is likely to increase during the next two days.
A persistent trough/wind discontinuity along the ‘trunk’ of the mainland amplified the poorly endowed monsoon features obtaining on Sunday.
The trough ran down from Jharkhand to north coastal Andhra Pradesh through Chhattisgarh headed by cyclonic circulation over Jharkhand.
It featured the confluence of opposing wind streams and resultant unstable weather.
Rainfall occurred at many places over Kerala and interior Tamil Nadu during the 24 hours ending Sunday morning.
Isolated rainfall occurred over Lakshadweep, coastal Andhra Pradesh, Telangana, coastal Tamil Nadu and Karnataka.
Forecast for the next two days said rain or thundershowers are likely at many places over Kerala and Lakshadweep and at a few places over interior Tamil Nadu, coastal and south interior Karnataka.
Isolated rain or thundershowers have been forecast over coastal Tamil Nadu, Puducherry, north interior Karnataka and coastal Andhra Pradesh.
A warning spoke about the possibility of isolated heavy rain over Kerala and Lakshadweep.
