The Australian Bureau of Meteorology has located signs of crucial level of support for the Indian monsoon emanating from the higher levels of atmosphere.
In updated assessment issued this morning, it said that a ‘weak burst’ in the Madden-Julian Oscillation (MJO) wave has been detected over the western hemisphere and Africa.
The MJO wave periodically transits the east African coast and passes over the Indian Ocean en route to the Maritime Continent (Indonesia et al) and the Pacific.
Though traversing the upper levels, the wave wields profound influence on weather at the ground level by promoting the cloud-building and rains.
When timed with the onset of monsoon in India, it helps rejuvenate the proceedings by setting up clouds and guiding the progression of rain over land.
It has also been associated with triggering storms by setting up low-pressure areas in the seas and helping them to grow in strength.
The Australian Bureau said that the latest burst of the MJO wave follows several weeks of little or no MJO signal in the tropics.
Onset Phase
The MJO can be difficult to detect during an El Nino, one of which is now strengthening over the Pacific, due to the strong shift in the cloud and wind patterns occurring during the event.
This week, most models indicate the MJO is likely to move slowly eastwards into the tropical western Indian Ocean, maintaining moderate strength.
The following week, most models suggest that it will weaken. When the MJO is over the Indian Ocean at this time of year, it can enhance monsoonal activity.
The Bureau cited Indian Met Department’s assessment that the monsoon may break out over Kerala ‘within the coming week.’
It remains to be seen how global models see the MJO impact over the onset phase.
Heavy Rain
The NCEP/GFS model of the US Climate Prediction Centre has been indicating the possibility of heavy rains over south peninsula during the week ending June 7.
But the following week will see a drastic reduction in rain, apparently after a low-pressure area in Arabian Sea sprints away to the Oman/Karachi coasts with available moisture.
The ‘low’ would represent a sign of the benign influence of the MJO wave on the monsoon as it oversees it from the heights.
The US model seems to attribute excess rain during the first week to this ‘low’ forming off the Mangalore coast, and likely resulting in very heavy rain in the city and neighbourhood.
The Indian Institute of Tropical Meteorology also has alluded to the possibility of a ‘low-pressure system’ forming in the Arabian Sea.