The Hindu Business Line : Projected strong flows revive cyclone talk

Thiruvananthapuram, May 27 Amidst indications that a monsoon-boosting Madden-Julian Oscillation (MJO) wave is set to sweep the Arabian Sea and the Indian Ocean, heavy rains are being forecast for the southwest coast during the first week of June.

The southwesterly flows are expected to be so strong that the European Centre for Medium-Range Forecasting (ECMWF) has revived talks (as of 5.30 a.m. IST on Tuesday) about a major cyclone spinning up off the Konkan-Karnataka coast around June 4.

The only model to share this outlook concurrently was one featured on the US National Centres for Environmental Prediction’s (NCEP) Climate Prediction Centre site. But it predicted that the system would move north along the coast and hit Gujarat.

According to the experimental Roundy-Albany prediction model, the system would be ‘so strong’ as to bring under its footprint almost the entire southwest coast of India, Gujarat, Sindh in neighbouring Pakistan, and Oman/Yemen to further west.

The ECMWF, too, predicts ‘a very strong system’ re-curving away from India’s southwest coast, heading straight west into the open waters of the Arabian Sea and intensifying several rounds before hitting Oman. The sheer strength would enable it to decimate all prevailing meteorological events to reach a ‘logical conclusion’.

A survey of major models, including the National Oceanographic and Atmospheric Administration (NOAA), the Earth System Research Laboratory and others of the NCEP, showed a ‘rainfall maxima’ sitting off and along the southwest coast of India and moving gradually to the west towards Oman.

What might go to lend some credence to the scenario is the ‘force multiplier effect’ of the MJO, which is forecast to become clearly established over the ‘monsoon home stretch’ in the central and east Arabian Sea by Friday (May 30). The widely tracked Wheeler MJO forecast model says the wave would peak during the five-day ending June 4.

Among the many influences of the MJO is its modulation of tropical cyclone activity. The whole area covering the peninsular India south of Gujarat and extending into the south-central Bay of Bengal would be brought under its influence in this manner.

MJO TENURE

This phase could likely witness the cyclogenesis (birth of a cyclone) off the Karnataka coast. The Wheeler Model says the MJO would be active over the Indian sub-continent through June 20. This is more or less corroborated by the Experimental Warning Programme (EWP) of the US National Weather Services, which says the wave could fade out latest by June 25.

An India Meteorological Department (IMD) update on Tuesday said that the monsoon has further advanced into some parts of south Arabian Sea and some more parts of Bay of Bengal. The cross-equatorial wind flows over south Arabian Sea are forecast to strengthen and deepen during the next three days.

Monsoon gateway

An east-west shear zone is also establishing over extreme south peninsula. On Tuesday, however, northwesterlies looping down to the south had prevented any appreciable northward progress of the upper level easterlies, an important attribute of monsoon.

The easterlies packing the Easterly Jet must be able to cruise along Chennai latitude to represent peak monsoon activity.