A well-marked but inconsequential low-pressure area over lies over the South-West Arabian Sea that is expected to become a depression by tomorrow (Sunday), but what is of import for the currently stalled North-East monsoon is a depression watch closer home to the East of Sri Lanka.
India Meteorological Department (IMD) has picked a cyclonic circulation over Equatorial Indian Ocean and adjoining South-East Bay of Bengal, which it expects to concentrate into a low-pressure area by Monday and further into a depression over South-West Bay of Bengal.
Track towards Lanka-TN coast
This depression is forecast to move in a typical West-North-West direction towards the coast of Sri Lanka and Tamil Nadu during the subsequent days, the IMD outlook said. This would expectedly revive the North-East monsoon yet again over the Tamil Badu coast from Monday itself.
Rains would scale up over the South Peninsula as a whole from Monday with scattered to fairly widespread rainfall accompanied with thunderstorms, especially over Tamil Nadu, while it would be isolated over the rest parts of the South Peninsula. Isolated heavy falls is likely over Tamil Nadu on Monday and isolated heavy to very heavy on Tuesday and Wednesday.
ECMWF outlook for rain spell
The European Centre for Medium-Range Weather Forecasts (ECMWF) said that moderate rain may lash the North-East coast of Sri Lanka first late into the night of Sunday (tomorrow). It would be Puducherry and the rest of the southern coast of Tamil Nadu that would get the heavy spell from Monday afternoon.
Chennai may receive the first heavy spell from Tuesday morning according to the ECMWF while it would be moderate over adjoining South Coast Andhra Pradesh coast including over Nellore. Light rain may filter into the adjoining interior right up Bengaluru in Karnataka.
Time for subsequent wave
By this time, the subsequent heavy rain wave would have struck Puducherry first again, followed by Chennai and then later moderately into interior Tamil Nadu, though heavy thunderstorms are indicated to the East and South-East of Madurai by Wednesday evening.
This would be followed by a third heavy wave of heavy rain for Puducherry, Chennai and adjoining South Coastal Andhra Pradesh by Friday, apparently aligned with the movement of the depression along the coast and a likely cross-over into South Coastal Andhra Pradesh.
IMD heavy rain forecast
In its forecast for Monday, the IMD has said that heavy rainfall is likely over Tamil Nadu and Puducherry. Thunderstorm with lightning may strike the Andaman & Nicobar Islands and Tamil Nadu and Puducherry. Squally weather (wind speeds reaching 40-50 km/hr) gusting to 60 km/hr (depression strength) is warned along and off the Tamil Nadu coast and the Gulf of Mannar. Fishermen are advised not to venture into these areas.
Chennai bloggers on cue
An extended forecast from Thursday to Saturday said that scattered to fairly widespread rain/thundershowers is likely over Tamil Nadu, Puducherry and Kerala. Isolated to scattered rainfall activity likely over the rest of the South Peninsula and isolated heavy rainfall over parts of the region.
The Chennai bloggers have been quick to tune their antennae and even went on to discuss the possibilities of a likely cyclone developing as part of the emerging buzz in the Bay of Bengal, though opinions are divided on the eventuality.