A moderate to strong ‘pulse’ of the monsoon-driving Madden-Julian Oscillation (MJO) wave has moved into the western parts of the Equatorial Indian Ocean (extreme South of the Arabian Sea).

The location and strength of this MJO ‘pulse’ has enhanced cloudiness and rainfall over the northern Indian Ocean and parts of the adjoining southern Arabian Sea, the Australian Bureau of Meteorology (BoM) said.

This may contribute to further movement to the North and development of the Indian monsoon, but the influence of the MJO wave may wane in the coming week, the BoM said.

This would scale down the enhanced rainfall pattern over the northern parts of the Indian Ocean and adjoining South Arabian Sea to near-average levels next week.

The average onset date of the Indian monsoon, defined as the date the monsoon onset occurs at the south-western coast of Kerala, is  June 1, it observed.

Normal rainfall expected

During the past week, the northernmost extent of the monsoon was well south of its normal position for this time of the year. As a result, the most recent forecast by the Indian Meteorological Department (IMD) is for the monsoon onset to occur around June 6.

Despite the slightly later than normal start to the monsoon, the IMD predicts close to normal rainfall during the monsoon season across India overall.

The El Nino conditions in the Equatorial East Pacific Ocean and temperature patterns across the Indian Ocean have been shown to influence India's monsoon.

El Nino-IOD influence

The delayed onset date this year may be related to the El Nino-like conditions that have been apparent at times in 2019, the BoM explained.

But its counterpart in the Indian Ocean, a positive Indian Ocean Dipole (IOD), which is expected to evolve during the course of the monsoon, is known to generate above-average rainfall.

On Tuesday, the IMD said the monsoon has further advanced into the southernmost parts of Arabian sea, some more parts of the Maldives-Comorin, south-west, south-east and east-central Bay of Bengal.

Cross-equatorial monsoon flows over the southern parts of the South Arabian Sea are likely to increase gradually favouring further advance of monsoon to some more parts of the South Arabian Sea, the Maldives-Comorin area, south-west, south-east and central Bay of Bengal by Wednesday.

An East-West wind shear zone of monsoon turbulence would develop across the extreme South Peninsula from Wednesday, leading to favourable conditions for onset of the monsoon over Kerala subsequently.

Monsoon conditions continue to establish over the neighbouring island nation of Sri Lanka, with showery and windy conditions (particularly in the South-Western parts) forecast to continue on Tuesday.