Rain or thundershowers are expected to continue over extreme south peninsular India (Kerala and South Tamil Nadu) and scale up from Monday.

This is as per a morning outlook of the India Meteorological Department (IMD), which has extended watch for a low-pressure area in Southwest Bay of Bengal for the next two to three days.

'Low' watch

Low-pressure area (‘low’) is a basic unit of a building weather system that grows into future depressions and cyclones.

In the instant case, the ‘low’ is forecast to intensify into a depression or even a cyclone as per some model forecasts.

Importantly, the US National Centres for Environmental Prediction sees an escalation of rainfall activity all over southern peninsula from May 13 (Monday).

This could signal the onset of Southwest monsoon over Andaman and Nicobar Islands, the country’s farthest outpost and the monsoon's first port of call in extreme Southeast Bay of Bengal.

Pre-monsoon weather

Meanwhile, pre-monsoon weather is establishing its presence over most parts of the country in the form of rain, thunderstorms and dust storms.   

A prevailing western disturbance, a land-based low-pressure system that stalks North, Northwest, East and Northeast India during this time of the year, is parked over Jammu and Kashmir.  

This weather feature is linked to Kerala in the South by a trough of lower pressure that snakes down across Chhattisgarh, Vidarbha and interior Karnataka.

The trough allows thunderstorms to build along its trunk, and brings thundery weather along the way and down to the South.

IMD forecast

The IMD has forecast thunder squalls would scythe through Odisha, Chhattisgarh, North Andhra Pradesh until this afternoon.

Dust storm has been forecast over East Uttar Pradesh and North Madhya Pradesh. Outlook for the next three days said similar weather for these regions and heavy rain for parts of the Northeast.

vinson.kurian@thehindu.co.in