The Hindu Business Line : Intruder ‘low’ cuts flows, rains have to wait

Thiruvananthapuram, June 4 Strong cross-equatorial flows have converged over the east-central Arabian Sea on Thursday to set up a ‘low’ with implications for the ongoing precipitation over the southwest coast.

The preparatory ‘cyclonic turning’ pronouncedly evident from the previous day got accentuated against the background of the warming seas and resultant convection.

A northwest track for lateral movement and a round of intensification, as indicated by the India Meteorological Department (IMD), would take the system away and cause part of the flows to be diverted.

The diversion will be reflected in subdued rainfall over the southwest coast, but only temporarily so, since another surge in the flows has been indicated after the next two days.

FLARING CONVECTION

The US Navy’s Joint Typhoon Warning Centre (JTWC) said that an area of convection has persisted some 960 km west-northwest of Kochi.

Satellite imagery showed flaring deep convection near a developing low level circulation centre (LLCC).

The disturbance lay beneath an area of favourable upper level diffluence (window effect) with moderate vertical wind shear and maximum sustained surface winds clocking 37 km/hr.

The JTWC assessed as poor the potential for the development of a significant tropical cyclone within the next 24 hours. But the Global Forecast System (GFS) of the US Fleet Numerical Oceanography and Meteorology Centre (FNMOC) and the Navy Operational Global Atmospheric Prediction System (NOGPAS) depicted an alternate scenario emerging over the Arabian Sea.

These models suggest that the ‘low’ would stay anchored over the Arabian Sea over the next two weeks to preside over the rainfall events over the southwest coast.

The system will pull in the flows that are shown to peak during this period.

Heavy to very heavy rainfall is being forecast along the coast up to Mumbai and even extending to south Gujarat during the period ending July 14, as per latest available updates by these models.

The European Centre for Medium-Range Weather Forecasts (ECMWF) too has predicted a northwest course for the ‘low’, but says the rain bands will spread along an arc from south Gujarat, adjoining south Pakistan and westwards to Oman.

WEAK BAY ‘LOW’

Meanwhile, model projections are in agreement over the prospects for a counterpart ‘low’ materialising over the Head Bay of Bengal around June 8. A rather weak system, it is shown later as crawling over into the West Bengal coast and moving in a westward direction to drive rain into central India.

This track will set the system up for a rendezvous with the rain bands associated with the prevailing Arabian Sea ‘low’, and together, they will trigger heavy rainfall over Gujarat and the Mumbai-Konkan belt.

An IMD update on Wednesday said that the current meteorological analysis suggested fairly widespread rainfall with isolated heavy falls is likely over the north eastern States, sub-Himalayan West Bengal and Sikkim during the next three days.

Rain or thundershowers have been forecast at many places over coastal Karnataka, Kerala, Lakshadweep and Andaman and Nicobar. Thundershowers have been forecast over south Konkan and Goa over the next two days, which will scale up, thereafter.

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