Global weather models suspect a storm may be evolving over the Maldives-Lakshadweep region in a week’s time, which could affect the timely onset of the Indian monsoon.

Storms forming during mid-May or later have the effect of unsettling the build-up phase of the monsoon, which normally hits Kerala on June 1.

The European Centre for Medium-Range Weather Forecasts says that by May 16, a preparatory low-pressure area would have moved in closer to Sri Lanka and Kanyakumari. Pune-based Indian Institute of Tropical Meteorology agrees, saying a ‘low’ is likely to form over South Arabian Sea (Maldives-Lakshadweep) by mid-May.

Strengthening southward

As if on cue, on Monday the India Met Department located a rudimentary form of the ‘low’ (trough) lying over Maldives-Lakshadweep.

According to the European agency’s forecast, this may strengthen and move towards Sri Lanka and Kanyakumari by May 17 and slide along the Kerala coast to reach Mangaluru by May 19.

What lends credence to this scenario is the expected arrival of Madden-Julian Oscillation (MJO) wave over the West Indian Ocean/South Arabian Sea during May 11 and May 17.

MJO wave arriving

The US Climate Prediction Centre sees the MJO wave intensifying rainfall activity over Sri Lanka and surrounding seas.

An MJO wave passes from West to East high in the atmosphere, but has a strong influence over ground weather in terms of its capacity to set up cloudiness, storminess and rainfall.

The wave also supports the mechanics of storm formation by adding clouds and moisture around a low-pressure area and driving it up in strength.

Meanwhile, the Indian Institute of Tropical Meteorology has indicated that the South Bay of Bengal (around the Andaman and Nicobar Islands) too may throw up a low-pressure area during May 11-17.

Heading east

This ‘low’ is likely to travel in an east-northeast direction towards southern Myanmar.

India Met Department has said that no part of the country will witness heat wave conditions until May 16, up to when forecasts are available.

In fact, heavy rain or thunderstorms/squalls have been forecast for many parts of North-West India, East India and Peninsular India during this period.

The US National Centres for Environmental Prediction says two-thirds of the country (save Rajasthan, Gujarat and West Madhya Pradesh) may get thundershowers between May 9 and 17.

In the following week, thundershowers will be mostly confined to the South Peninsula and the East, as more parts of West and North-West India dry up.

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