The Hindu Business Line : ‘Break’ throws open rain window for Tamil Nadu

Thiruvananthapuram, July 14 The southwest monsoon may be going into a weak phase (euphemism for ‘break-monsoon’) over the next 24 to 36 hours in the context of the land-based and weather-driving trough having shifted to the Himalayan foothills.

This may not mean much for the moisture-stressed peninsular interior which has not seen rains over the past 28 days but could presage trouble for flood-prone areas in east and northeast India.

As is the rare but interesting case, southeast Tamil Nadu too will garner its due share of ‘monsoon rainfall’ during the ‘break.’ This is because upper level easterlies weaken during this phase, allowing the southwest Bay to breathe life into the hinterland.

Coastal and interior Tamil Nadu southward of Puducherry will witness fairly widespread rainfall, according to a meteorological expert in the Government who wished to remain anonymous. Along with Bihar and Jharkhand, these areas would be the focus for enhanced rainfall during the next three to five days.

NOT PROLONGED

Emerging conditions in Bihar and Jharkhand would need some close watching, but the situation may not get out of hand since the heavy rain belt is seen petering out in three days’ time. The monsoon trough would then gradually shift southward to its normal position, when rains are seen reviving along the southwest coast.

The precipitation triggered (from July 18) would be confined to Lakshadweep, Kerala, coastal Karnataka, south Tamil Nadu and further south to Sri Lanka. A ridge-like formation (high pressure) in the southwest Arabian Sea will make winds blow in a west-northwesterly axis with a core of dry continental air from West Asia.

This will cause the moisture-laden winds to blow to the south and southeast, skipping the better part of the west coast and preventing rains from penetrating interior peninsula. The wait for the badly needed round of rains here is likely to be extended by another five days.

The affected Met subdivisions - North interior Karnataka, madhya Maharashtra, Marathawada and Vidarbha - would have to wait until ‘a slow but sure-footed wave of rainfall’ inches its way up from coastal Tamil Nadu around July 25 or so.

POTENTIAL WAVE

This wave has already been traced moving north from the Equator, and is expected to coalesce with the convergence zone being set up as winds from the Arabian Sea ridge steer round the peninsular tip into Tamil Nadu. The northward propagation of this zone of unsettled weather has a crucial bearing on rain prospects for peninsular north.

But the expert sought to rule out cause for worry on this front, since there is clear evidence of a ‘potential wave’ in the making capable of salvaging the situation to some extent in the deficient areas. His advice to farmers was to delay transplantation of rice till such time as they are sure of the prospects and timing of the impending rainfall.

An India Meteorological Department update on Monday said that isolated heavy to very heavy rainfall is likely over the Northeast, sub-Himalayan West Bengal, Sikkim and Bihar during the next two days. Isolated heavy rainfall is also likely over east Uttar Pradesh. The three days that follow would see scattered to fairly widespread rainfall activity over the northeast, sub-Himalayan West Bengal, Sikkim, the Gangetic Plains, coastal Karnataka and Kerala.

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