The Hindu Business Line : Cyclone watch on as parent ‘low’ forms

Thiruvananthapuram, May 28 The European Centre for Medium-Range Weather Forecasts (ECMWF) and the Roundy-Albany models maintained their cyclone watch in the Arabian Sea on Wednesday.

The ECMWF chose to slightly tinker with the model by scaling down the strength, altering the track for lateral movement and delaying the landfall by a few days. The system is shown to land to the south of Oman/Yemen around June 7.

The Roundy-Albany model persisted with their outlook for the system to head north and hit Gujarat. The only model prognosis suggesting anything similar was the gale probability model from the Ensemble Forecast System (EFS) of the US Navy’s Fleet Numerical Meteorology and Oceanography Centre (FNMOC).

This model predicted gale-speed winds progressing along the southwest coast up till the Konkan, just south of Mumbai. These winds were indicated to consistently blow in the range of 35 knots (65 km/hr) or above up to June 4.

PARENT ‘LOW’

Another model that sees the system intensifying in such a linear fashion is the US-based Centre for Ocean-Land-Atmosphere (COLA) studies. It saw the parent ‘low’ taking shape just west of Maldives accelerate to become a depression, track northwest to near-cyclonic strength in the central Arabian Sea during the week ending June 4.

Meanwhile, an India Meteorological Department (IMD) update on Wednesday said that the previous day’s trough of low over southeast and adjoining east-central Arabian sea off south Karnataka and north Kerala coasts had intensified to become a low-pressure area over southeast and adjoining east-central Arabian Sea.

The cyclonic circulation over Lakshadweep and neighbourhood had merged with the above system. This ‘low’ will be watched for further intensification, and would act as the parent ‘low’ for the larger system in the Arabian Sea.

COLA also saw a blow-up of rainfall over the Kerala-Karnataka coast as well as to the south of Mumbai during the week ending June 13. Concurrent bursts in thundershower activity were also indicated for the North-East.

ONSET DATE

Meanwhile, an IMD update sounded less sure about a possible onset of monsoon over the Kerala coast by Thursday (May 29), the date set by it for declaration of the same.

It merely said an east-west shear zone had been established across the extreme south peninsula. But wind speeds lagged, although numerical weather prediction models continued to indicate strengthening of the westerly to southwesterlies over the south Arabian Sea and the extreme south peninsula during the next three days.

A warning valid for the next two days indicated that isolated heavy rain or thundershowers are likely over Lakshadweep Islands. Following this, scattered to fairly widespread rainfall activity is likely over south peninsula and the North-East.

Rain or thundershowers are likely at a few places over coastal Karnataka and Kerala during the next 24 hours and would scale up in intensity thereafter. South Konkan, Goa and south Madhya Maharashtra are also expected to come under a wet spell during this period.