Monsoon ‘on track,’ says Australian model

The Australian Bureau of Meteorology (BoM) has predicted that the southwest monsoon remains on track to arrive on time over Kerala in late May or early June.

The BoM assessment was contained in a weather update of the tropics issued a couple of days ago.

NO MJO SUPPORT

Onset dynamics this year would, however, not have the support of a periodical Madden-Julian Oscillation (MJO) wave.

This wave of lower pressure travels at high levels in the atmosphere from west to east over the Indian Ocean at regular intervals.

It has alternating dry and wet phases. The wet phase has been known to be the harbinger of monsoon onsets, low-pressure areas and storms.

Back-up of a timely wet phase of the MJO wave would make for spectacular onset of the monsoon along the Kerala coast.

WEAK RAINFALL

The BoM has noted that ‘suppressed convection’ (weak rains) would prevail over the next fortnight across the central Indian Ocean.

This would gradually shift eastwards towards the Philippines, in line with the eastward movement of the prevailing dry phase of the MJO.

But monsoon onset can take place on its own strength, too. According to a US-based tracker, a low-pressure system in the Bay of Bengal could likely prove the trigger.

This system is shown as intensifying, but prevailing strong westerly-to-northwesterly winds would swing it towards an east-northeast track towards Myanmar.

ONSET PHASE

In the process, it would also drag the monsoon current in and across the southwest coast, likely precipitating the onset.

The US tracker has been suggesting a May-25 timeline for the system in the Bay to form and get into the act. The Australian model appears to concur with this.

Outlook for formation of a peer system is maintained for the Arabian Sea, but it might get weakened in the face of the stronger ‘pull’ from the Bay.

vinson.kurian@thehindu.co.in

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