Tuesday's well-marked low-pressure area over East-central Bay of Bengal has intensified into a depression, an India Meteorological Department (IMD) said on Wednesday evening. The storm has been lying centred about 700 km east of Visakhapatnam, 550 km southeast of Gopalpur and 550 km south-southeast of Digha since the afternoon.
The system is likely to move in a west-northwesterly direction towards the South Orissa coast during the next three days. The IMD bulletin did not mention about the prospects for further intensification, though international models say enabling conditions for the eventuality have been emerging.
The sea-surface temperature over large parts of the Bay continued to be above the threshold level needed for sustaining tropical storms. Upper level divergence that sets up the window for the system to ‘breathe' through the top and moderate vertical wind shear were two variables that boosted the prospects for further strengthening.
The Joint Typhoon Warning Centre (JTWC) of the US Navy took note of flaring deep convection around a low-level circulation centre.
‘FAIR' POTENTIAL
It assessed as ‘fair' the potential for the development of a significant tropical weather system during the next 24 hours. Meanwhile, it is increasingly becoming clear that the West Pacific-South China Sea-Bay of Bengal basins would need to calm down before the northeast monsoon can unfold along India's southeast coast.
Hectic activity in the Bay is not allowing the seasonal anticyclone over Northwest India to extend to lower latitudes and preside over the simultaneous exit of southwest monsoon and entry of the northeast monsoon.
FOLLOW-UP STORM
Meanwhile, the European Centre for Medium-Range Weather Forecasts (ECMWF) and a couple of other models have maintained their watch for another tropical storm in the Bay of Bengal around October 23. The system is forecast to be lapped up by a westerly trough approaching from Northwest India and hurled over the West Bengal coast around that time. This would coincide with the formation of a very powerful system making landfall over Southwest China with implications for entire Indo-China as well.
STRONG MJO
International models point to a situation where a very strong wet phase of the Madden-Julian Oscillation (MJO) wave has ‘lit up' the South China Sea and the West Pacific.
An equally strong dry but alternating phase of the MJO has been on view over Equatorial Indian Ocean and the South Indian Peninsula over the past few days.
The dry MJO phase does not help the cause of the northeast monsoon, though active monsoons have been known to prosper despite it.
The wet phase of the MJO, an upper level disturbance that transits the regional seas periodically, is known for triggering monsoon onsets and formation of ‘low's, depressions and even cyclones.
SUPER TYPHOON
The Climate Prediction Centre of the US National Weather Services had extrapolated earlier last week of the brewing storminess in the West Pacific/South China Sea sparked by a peaking wet phase of the MJO.
As mentioned earlier, a super typhoon is in the making in the South China Sea around October 23 after a low-pressure area getting generated in the West Pacific crosses the Philippine archipelago and slides into the South China Sea.
In fact, the JTWC has already picked on a preparatory tropical depression over the West Pacific and put it under watch for intensification as a cyclone very soon.
TheECMWF sees it unleashing its fury over Southwest China, Hong Kong, Vietnam and the larger Indo-China around that date.
The Ensemble Forecast System of the US Navy's Fleet Numerical Meteorology and Oceanography centre has also supported the outlook for this super typhoon.
Since it is a westward propagating system, a remnant is expected to call in over the Bay of Bengal as well and set up a ‘low' in due course.
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