The Hindu Business Line : All set for seasonal heating up of land

Thiruvananthapuram, April 17 It is now becoming increasingly apparent that Typhoon Neoguri would slam the Chinese coast within the next 36 hours but there are indications that it will wind down to being a tropical storm just before landfall. The city of Qionghai could bear the brunt of the land-falling storm, according to projections by the London-based storm-tracker Tropical Storm Risk Group. But it will be sometime before Bay of Bengal in the neighbourhood resonates, though some models point to enhanced convection being triggered in the southwest Bay around April 20.

Over land, the heating process will resume in right earnest from Friday, notwithstanding the nuisance value from a feeble incoming western disturbance drifting into the northwest around April 22.

On Thursday, the formation of an anomalous trough towards the east of India seemed to have set back the initiation of the ‘heat low’ over the northwest. Mean sea level pressure showed a high of 1,008 millibars over Rajasthan against 1,002 millibars the previous day.

The pressure comes down with rising heat, but unlike in a conventional ‘low-pressure’ environment, it does not lead to precipitation due to the play of a peculiar set of meteorological factors in the region. The ‘heat low’ would progressively anchor the crucial monsoon trough lying along a northwest-to-southeast alignment.

LESS MARKED

The prevailing western disturbance over Himachal Pradesh and an adjunct cyclonic circulation over east Uttar Pradesh were moving away, leaving room for the mercury to climb back to the high 40s over the northwest Friday onwards. The trough in the accompanying Westerlies had also become less marked relative to the previous day.

Maximum temperature were 40-43{ring}C over Madhya Pradesh, Vidarbha, east Uttar Pradesh, Chhattisgarh and adjoining Orissa and Jharkhand. Model predictions suggested that the north-south trough in the east will cause scattered rain or thundershowers over sub-Himalayan West Bengal, Sikkim and the northeastern States during the next 3-4 days.

The trough from Vidarbha to south Tamil Nadu now runs from Marathwada to south Tamil Nadu through south Madhya Maharashtra and interior Karnataka. Alternatively, this will act as the ‘line of wind discontinuity’ where mutually repulsive winds would set up a meandering north-to-south corridor of unsettled weather.

EMBEDDED WHIRL

India Meteorology Department said that this ‘unstable’ corridor already hosts an embedded cyclonic circulation over south Madhya Maharashtra with the winds wrapping around. Another cyclonic circulation lay over east Madhya Pradesh and neighbourhood.

An existing cyclonic circulation over west Rajasthan and neighbourhood has become less marked.