Monsoon may reach Andaman Sea next week

The European Centre for Medium-Range Weather Forecasting (ECMWF) has predicted that the South-West monsoon may hit Sri Lanka around May 20, a week before schedule.

The US Centres for Environmental Prediction (NCEP), too, shows southwest Sri Lanka being hit during the week ending May 21.

(Agencies quoting the Union Minister of State for Earth Sciences, Mr Prithiviraj Chavan, said monsoon will arrive on May 30.)

WIND SPEED

The Climate Prediction Centre (CPC) of the US National Weather Services sees low level winds gathering pace beyond May 22 to precipitate a likely onset over Kerala.

The International Research Institute (IRI) for Climate and Society at Columbia University suggests that monsoon would hit the Andaman Islands, the first outpost in the Indian territorial waters, as early as May 17 (Monday). Wind speeds in the Andaman Sea are already in the 15 to 30 km/hr, according to the Thailand Met Department, but needs to steadily clock between 27 to 30 km/hr for onset to happen.

RAINS FOR TN

The NCEP has gone on to signal heavy precipitation over the Tamil Nadu coast and over the north-eastern States concurrently during May 21 to 28.

Meanwhile, the CPC points towards the possibility of enhanced convective phase of the Madden-Julian Oscillation (MJO) wave and numerical weather forecast guidance forcing tropical storm formation for the Arabian Sea during next week.

The CPC outlook also said that the active MJO phase would trigger enhanced rainfall for the eastern Indian Ocean and the maritime continent (Indonesia, et al) during this phase as well as the southern tip of Sri Lanka.

Interestingly, it sees possible tropical storm spinning up over the southwest Bay of Bengal thereafter.

BAY STORM

This is exactly the scenario being envisioned by Prof Paul Roundy, a leading US-based ocean weather forecaster, to unfold around May 25.

Both systems would be oriented southwest to northeast, which means the Arabian Sea system would cross the west coast during the onset phase.

By the same token, the Bay of Bengal system would be guided north-northeast towards for a rendezvous with the West Bengal or adjoining Bangladesh coast.

Meanwhile, experts are of the view that the cross-equatorial monsoon current is building across the East Indian Ocean with clouds massing around.

Unlike in the Arabian Sea, this monsoon current needs to cover much lesser ground to precipitate the onset in the Bay of Bengal.


The Arabian Sea current has to travel along the Equator until the east African coast from where it makes a southwesterly turn to enter the far west Arabian Sea. From here, it has to travel quite some distance towards the Kerala coast.

Meanwhile, pre-monsoon activity was apace in the east and northeast even as a western disturbance is expected to trigger some activity over parts of northwest India.

India Meteorological Department (IMD) has warned that thunder squalls would occur at isolated places over Jammu and Kashmir, Himachal Pradesh, Uttarkhand, West Bengal, Sikkim, the north-eastern States, Punjab, Haryana, Uttar Pradesh and Orissa during the next two days.

Isolated heavy to very heavy rain or thundershowers would occur over Arunachal Pradesh, Assam and Meghalaya.

The causative trough from southwest Jharkhand to northeast Assam across Gangetic West Bengal, Bangladesh and Meghalaya persisted.

The main north-south trough tracked down from east Madhya Pradesh to south Tamil Nadu across Vidarbha, Marathwada and Karnataka.

The western disturbance over Jammu and Kashmir and adjoining north Pakistan featured an induced upper air cyclonic circulation over north Rajasthan.

It is likely to affect the western Himalayan region during next two days. A fresh western disturbance is likely drift in Sunday.

Satellite imagery revealed presence of convective (rain-causing) clouds over parts of Arunachal Pradesh, south Arabian Sea, south Bay of Bengal and the Andaman Sea. Low to medium clouds (partly clouded conditions) were seen over parts of western Himalayan region, east and peninsular India and remaining parts of the north-eastern States.