Monsoon may have to wait until next week to revive

The monsoon has advanced to more parts of Maharashtra, Chhattisgarh, Bengal, Assam and Meghalaya this morning, even as it negotiates the last few days of the onset phase that began on May 29. It is expected to cover more parts of Odisha, the remaining parts of the North-Eastern states and some parts of Bengal and Sikkim during the next two days, the India Met Department (IMD) said.

WEAK PHASE

Thereafter, it might go into a weak phase over East and Central India, but rains are forecast to continue along the West Coast, at times heavy to very heavy at isolated places. Barren westerly to north-westerly winds have taken over the vast plains of North-West India, which signals the customary weak phase of the South-West monsoon.

For the monsoon to revive, it becomes inevitable that a suitably endowed low-pressure area develops in the Head Bay (around Kolkata) of Bengal and fans in the monsoon easterlies into the hinterland.

This process becomes easier under the watchful eyes of a Madden-Julian Oscillation (MJO) wave that crosses the North Indian Ocean region (Arabian Sea and Bay included) periodically. Traversing the upper levels of the atmosphere, the wave packs moisture, heavy rain and convection (the process of cloud-building) with a beneficial impact on weather under its footprint.

MJO WAVE NEXT WEEK

Global models indicate that the next 'wet phase' of the MJO wave would be active over the region towards June-end, boosting the formation of low-pressure areas and monsoon onset/ revival.

The previous wet phase wave was responsible for setting up two cyclones in the Arabian Sea and the onset of the monsoon, followed by enhanced activity in the Bay topped up by formation of a 'low.'

That 'low' went on to become a depression, but strayed into the Bangladesh coast taking away the moisture and rain, has weakened since, and is lately located over Tripura as a 'low.'

The original MJO wave, meanwhile, continued to travel to the East (maritime continent, South China Sea and the North-West Pacific), has since set up storms there, and is weakening now.

The Australian Bureau of Meteorology confirms this, but significantly adds that the next MJO wave would become active over the Indian Ocean region from next week.