Thiruvananthapuram, May 31
India Meteorological Department (IMD) has declared the onset of monsoon over the Kerala coast on a day when it also saw a prospective cyclone brewing in the Arabian Sea.
The IMD joined peer numerical weather prediction models to project that the depression (spinning up overnight from a low') over east-central and adjoining west-central and south Arabian Sea would intensify into a cyclonic storm.
LIKELY LANDFALL
Importantly, it sought to posit the system towards making a landfall over the Gujarat coast after a re-curving from a two-day initial northwesterly to north-northwesterly track.
Though seen as tearing apart the onset phase, the cyclone might not impact monsoon flows expected to regroup from the south from the weekend, according to the European Centre for Medium Range Weather Forecasting (ECMWF).
In this manner, the Kerala coast may just be bracing for a second and more orderly onset with the flows being directed copybook style into southeast and adjoining south Arabian Sea and contiguous equatorial Indian Ocean and Bay of Bengal.
The US Navy's Joint Typhoon Warning Centre (JTWC) said that the Arabian Sea storm would take advantage of a host of favourable factors to ramp up in strength.
These included a boiling-hot' seawaters at 31 deg Celsius, good window effect at the top that enables the system to breathe and moderate vertical wind shear (change in wind speed and direction with height).
Based on building deep convection and favorable surface conditions, the JTWC assessed as good' the potential for the system to develop as a significant tropical cyclone.
WIDESPREAD RAIN
The IMD said that the Arabian Sea storm may trigger fairly widespread rainfall with isolated heavy to very heavy falls over coastal areas of Gujarat from Thursday.
Squally winds with speed reaching 45-55 km/hr would commence along and off Gujarat coast from the previous day.
Sea condition will be rough to very rough along and off Gujarat coast from Wednesday and fishermen are advised not venture into the sea during that period.
According to the ECMWF, the cyclonic storm (to be called Phet') might race close towards the Oman coast by Thursday.
But a large westerly trough coming in from the opposite direction would drop down its trunk' into north Arabian Sea and pick' the storm to swing it across Gujarat and adjoining Pakistan by Saturday.
The system would still pack some punch after landfall, and unleash heavy rains over entire Gujarat, west Madhya Pradesh, south-east and adjoining southwest Rajasthan, the ECMWF said.
It is shown as weakening in strength appreciably as it moves further northeast into east Rajasthan and adjoining Haryana and Delhi by Sunday before being guided as a remnant circulation over Uttar Pradesh and Bihar.
MONSOON ADVANCE
On Monday afternoon, the causative depression was centred about 1,050 km southwest of Mumbai and an equal distance away from south-southwest of Naliya.
In one fell swoop, the monsoon current was shown as having covered entire Kerala with the northern limit passing through the northern-most district of Kannur, and Salem and Nagapattinam in neighbouring Tamil Nadu.
Conditions are favourable for its further advance into some parts of central Arabian Sea, coastal and south interior Karnataka and Goa during the next two days.
Further advance of monsoon will depend upon the intensity and direction of movement of the storm, the forecast said.
A satellite imagery showed convective clouds over parts of southeast and east-central Arabian Sea and Andaman Sea.
Forecast up to Saturday suggested fairly widespread rain or thundershowers over Kerala, Lakshadweep, coastal Karnataka, the Northeastern States and Andaman and Nicobar Islands.