The Hindu Business Line : Westerlies force a reset of cyclone watch

Thiruvananthapuram, May 23 India Meteorological Department on Friday maintained the watch for a ‘low’ in the southeast Arabian Sea even as the capricious westerlies forced the European Centre for Medium-Range Weather Forecasts (ECMWF) to once again ‘reset’ a cyclone watch.

Latest ECMWF forecast charts showed a tropical storm lying in wait over the waters off Oman/Yemen for the right ‘window’ to run down the home stretch linking a ring of geography spanning Yemen, Oman, Sindh and Gujarat in India.

The strong westerly wind regime over India-Pakistan has left the forecasters on tenterhooks, with consensus view now veering round to the possibility of the ‘low’ in the southeast Arabian Sea intensifying and moving to the northwest initially.

Hasty retreat

The prevailing western disturbance has dipped unusually low to southern Indian latitudes stonewalling the progress of the monsoon current into the landmass. The brewing Arabian Sea ‘low’ has no go but move northwest where the warm seawaters are ideal for further growth and intensification.

In this context, the arrival of a fresh western disturbance around May 26/27 is being closely watched in terms of amplitude and depth for the likely impact on the Arabian Sea system.

The prevailing westerly has triggered unsettled weather all over northwest, central and east India over the past few days. Thunderstorms, squalls and spraying rain have punctuated the weather for days together in these regions. The heating of the landmass has all but stopped, with mercury plummeting to record lows at many places.

Pilots relieved

The evolving weather has surprised even commercial pilots, who are relieved that they would not need to contend with the turbulence resulting strong `updraft’ of air from a heated landmass and concurrent moisture incursion.

Speaking to Business Line, Captain Paresh Nerurkar, a Senior Pilot and Deputy General Manager (Operations) with Indian Airlines, said that landing manoeuvres posed a real challenge during peaking summer interspersed with moisture feeds extended by western disturbances.

Turbulence can be hazardous, having the potential to cause overstressing of the aircraft or loss of control. Thunderstorm vertical currents may be strong enough to displace an aircraft up or down vertically.

Capt Nerurkar singled out places such as Patna, Ranchi and Bhubaneshwar, among others, as ‘problem spots’ where pilots have a tough time holding the ‘big bird’ in balance. The ground control find itself flooded with guidance queries from approaching aircraft. But no such emergency existed now, thanks to the cooled-than-normal landmass.

THUNDER SQUALLS

An IMD warning valid for the next 48 hours said thunder squalls accompanied with hailstorm are likely over Punjab, Haryana, east Rajasthan, Chandigarh, Delhi, Uttar Pradesh, Uttarakhand, Jharkhand, Bihar, north Orissa, West Bengal and Sikkim. Isolated heavy rainfall is likely over the north-eastern States.

The cyclonic circulation embedded in the prevailing western disturbance and perched above Pakistan and adjoining Punjab and north Rajasthan persisted on Friday. A trough extended from this system to Jharkhand across Haryana, south Uttar Pradesh and north Madhya Pradesh.

As was the case on Thursday, moisture incursion from the Arabian Sea and the Bay of Bengal added to the instability in the Indo-Gangetic plains. Scattered to fairly widespread rain or thundershower with isolated thunder squall or hail has been forecast for this region and adjoining central India during the next two days.

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