Day temperatures are likely to rise by 3-5°C over most parts of the country during the next five days but India Meteorological Department (IMD) sees no heat wave conditions anywhere during this period.

Heating of North-West India and Central India will materialise even as projected cyclone Mocha barrels through the central parts of the Bay of Bengal and away from India’s coast. At least two global models see the cyclone ramping up probably to class-topping Category-5 strength (near-super cyclone) as it races towards Myanmar.

On Sunday morning, a preparatory cyclonic circulation lay over the South-East Bay. The IMD, has however, pushed back the formation of a low-pressure area in the same region by a day to Monday.

‘Heat low’ building late

Differential heating of the land vis-a-vis the adjoining sea sets up the required temperature and pressure gradient for monsoon winds to blow in. The land heats up faster than the ocean and hosts a ‘heat low’ over the subcontinent. 

Meanwhile, the US Climate Prediction Centre said a dry phase of the Madden-Julian Oscillation (MJO) wave will prevail over the South Peninsula from May 17 to 23. The onset of the monsoon may not happen unless a wet MJO phase arrives. 

Wet MJO phase

A wet phase of the MJO phase represents a passing wave of low-pressure, clouds and moisture that exits the East African coast and enters the Indian Ocean (the Arabian Sea and the Bay of Bengal).

The wave can influence weather at the ground level and set up low-pressure areas or depressions. It can also therefore preside over the onset of the monsoons in areas it passes over.

Global models see a moderately strong wet MJO wave drifting in over the Arabian Sea after June 4 and staying active for the next 10 days (until June 14).

It could likely trigger the onset of the South-West monsoon over Kerala late by a few days this time round. The IMD is expected to announce the expected date of onset next week in keeping up with its usual mid-May timeline.