An incoming ‘active’ (high-intensity) western disturbance extending its reach from South-West Iran was forecast to start affecting weather over North-West India from Tuesday for three subsequent days setting off rain, thundershowers, lightning, hail and high winds. This would drastically lower day temperatures from their prevailing highs over North and East India. 

A predecessor disturbance has just left India and temperatures had peaked in its rear. These will now be doused by the fresh disturbance. Proximity to the outgoing disturbance will continue to bring widespread to heavy rainfall over North-East India as pre-monsoon rain peaks in the rugged terrain. 

Heavy rain for North-East

India Meteorological Department (IMD) has predicted light to moderate to fairly widespread to widespread rain, thunderstorms, lightning and gusty winds over Assam and Meghalaya for the next two days. Heavy rain is likely over parts of Assam and Meghalaya until Friday, and over Nagaland, Manipur, Mizoram and Tripura from Wednesday to Friday. 

Light to moderate to fairly widespread to widespread rain with thunderstorms, lightning and gusty winds are likely over the hills of West Bengal and Sikkim. It will be isolated to scattered with thunderstorms, lightning and gusty winds over the rest of East India until Saturday. Heavy rain may lash parts of the hills, while hailstorms may strike parts of Bihar, West Bengal and Sikkim.

Pre-monsoon active

The South Peninsula, especially Kerala, has been witnessing brisk pre-monsoon activity for the past few days. The North-East and the South are two geographical regions that receive the monsoon one after the other (the Bay of Bengal arm calls in at the North-East and the Arabian Sea in Kerala). Light to moderate to isolated to scattered rainfall is forecast for many parts of South India for next five days.

Also read: Can India tame the impending El Niño?

Monsoon progress slow

The progress of the monsoon continues to be slow, with the IMD saying the Bay arm that hit the South Andaman Sea may remain stagnant for the next two days. A powerful cyclone (typhoon) in the West Pacific, named Mawar, is diverting flows towards itself and away from India. The impact on the larger monsoon system is clear from a revised update on onset over neighbouring Myanmar. Its Department of Meteorology and Hydrology said the monsoon is likely to set in over the southern parts (where it arrives first over the country) during a four-day window valid until Wednesday.