'Low’ in Bay of Bengal pushed back by two days

India Meteorological Department (IMD) has this (Sunday) morning pushed back the outlook for formation of the first and crucial pre-monsoon low-pressure area in the Bay of Bengal to Tuesday.

An existing western disturbance, just in the process of exiting northwest India, and a follow-up westerly system may have a big say on the timing and strength of the ‘low.’

An IMD outlook said that a fresh western disturbance would affect western Himalayan region and adjoining plains from May 5 (Thursday) onwards.

It also said that an upper air cyclonic circulation, widely seen as the progenitor of the ‘low,’ persists over central parts of south Bay of Bengal persist.

Global forecasters have been looking for a weather system that would take shape just to the northwest of the Andaman and Nicobar Islands and seek out a warmer pool of waters to east-northeast.

The higher sea-surface temperatures, aided by westerly winds associated with the western disturbance(s), are expected to guide the system towards the Myanmar coast by the end of this week.

In the process, the ‘low’ could intensify just a notch into being ‘well-marked,’ according to some of the global tracker models.

The IMD projections, however, signal to the possibility of the ‘low’ triggering a slow but intense churn in the Bay as a whole during the course of the week.

Satellite pictures early on Sunday morning showed the presence of convective (rain-bearing) clouds over parts of sub-Himalayan West Bengal, west Assam, Vidarbha, Tamil Nadu, southeast Arabian Sea, east-central and south Bay of Bengal and Andaman Sea.

A short-term outlook by the IMD and valid until Wednesday said widespread rain or thundershowers would break out over Andaman and Nicobar Islands.

It would be scattered over Karnataka, Kerala and Lakshadweep and isolated over rest of south peninsula India.

However, the rainfall activity is expected to relent over Andaman and

Nicobar Islands from Tuesday, indicating the away-movement of the core rain

belt.

Meanwhile, the western disturbance over Jammu and Kashmir and neighbourhood is moving eastwards but an upper air cyclonic circulation that it helped induce is persisting over Punjab and adjoining central Pakistan persists.

This has prompted the IMD to issue a weather warning that spoke about the possibility of isolated thunder squalls stalking the outback of Bihar, east Madhya Pradesh, east Uttar Pradesh, Jharkhand, Chhattisgarh, Orissa and West Bengal and Sikkim.

Isolated dust storms or thunderstorms have also been warned of over Punjab, Haryana and west Uttar Pradesh.

The other upper air cyclonic circulation over east Bihar features a southward-bound trough running down to Tamil Nadu across Jharkhand, Chhattisgarh and Andhra Pradesh.

This trough could be the playground for weather systems thanks to incursion of moisture laden winds and pumped in from a northeasterly direction interacting with the dry westerlies over land.

An extended forecast until Friday said that scattered rain or thundershowers would occur over the Northeastern States and adjoining east India.

Mainly dry weather would prevail over northwest and adjoining west and central India.

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