The Hindu Business Line : Wet weather to grow into west, northwest

Thiruvananthapuram, Nov. 18 The prevailing wet weather over southern peninsula, which promises to spread into the west and northwest, is despite the growing footprint of a suppressed convection phase from a planetary-scale Madden-Julian Oscillation (MJO) wave.

The MJO wave with its alternating dry and wet phases has a say on prevailing regional weather, while transiting periodically from West Africa into the Indian Ocean and into the Pacific.

“The uniqueness about the Indian monsoon regime is that while being decidedly responsive to the wet phase of an MJO wave, it can hold itself together reasonably well even in the face of its alternating dry phase,” said Dr Akhilesh Gupta, Senior Advisor to the Ministry of Science and Technology.

This is attributed to the inherent dynamics of the Indian monsoon regime, Dr Gupta told Business Line. This apparent dichotomy could not be more evident than during the short-duration northeast monsoon (two months against the four months of southwest monsoon) during when MJO peaks are commensurately fewer.

RARE OCCURRENCE

“We have even had the odd tropical cyclone develop during the suppressed convection phase of an MJO,” Dr Gupta said of the rare occurrence of intense sea-based weather systems conventionally identified with peak MJO phase.

Leading international models concurrently show that the equatorial Indian Ocean covering Sri Lanka and the southern Indian peninsula slipping under the influence of a dry MJO phase even as the air over the southern peninsula is awash with moisture.

Erstwhile Bay of Bengal cyclone Khai-Muk had helped direct an atmospheric river of moisture to flow inland. An easterly wave-in-the-making (seen by some models to strengthen to higher levels) is now forecast to pump incremental moisture into the peninsula.

Almost in tandem, an incoming western disturbance with an embedded trough is forecast to mop up moisture from the Arabian Sea to be smeared over northwest and adjoining central India.

The India Meteorological Department (IMD) on Tuesday said in its update that the westerly system would likely cause scattered precipitation over western Himalayan region and adjoining northern plains from Wednesday until the weekend.

In view of moisture incursion and confluence of different air masses, isolated rain or thundershowers are expected to break out over Gujarat, east Rajasthan, west Madhya Pradesh, Konkan, Goa and Madhya Maharashtra during the next two days.

ELEVATED MERCURY

Due to the prevailing southerly winds and cloudy conditions, the minimum temperatures are 5 to 8 degree Celsius above normal over central India and adjoining areas. These warm conditions are likely to prevail during the next two days. Thereafter, with change in the wind pattern, the temperatures are likely to fall, the IMD said.

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