IMD: Cyclone in the making in Arabian Sea, near Africa; depression nearer home

It is now becoming clear that the Arabian Sea basin will host yet another cyclone, the fourth in the current series during the North-East monsoon. However, the system will be far away, close to East African shores. Nearer home, a prevailing low-pressure area over Lakshadweep and the adjoining South-East Arabian Sea, too, has been building up traction and may intensify into a depression as early as tomorrow (Tuesday).

The first one lurked through Monday as a well-marked low-pressure area over the South-West Arabian Sea and the adjoining Equatorial Indian Ocean. It may ramp up into a depression into the night and later into a cyclone. It is likely to move West-North-West towards the Somalia coast by Tuesday.

Likely cyclone and depression

The two storms are aligned almost along a straight line and their combined effect will be felt most in Lakshadweep. The India Meteorological Department has issued a heavy rainfall warning for Lakshadweep where the proceedings will begin as light to moderate rainfall at most places with heavy to very heavy rainfall at isolated places until tomorrow (Tuesday); and light to moderate rainfall at many places with isolated heavy raiinfall on Wednesday, before reducing in intensity.

For Kerala, light to moderate rainfall has been forecast at most places with heavy to very heavy rainfall at isolated places until tomorrow.

As for Tamil Nadu, Puducherry and Karaikal, it should be light to moderate rainfall at many places with heavy to very heavy rainfall over the interior parts until tomorrow. This will be followed on Wednesday by light to moderate rainfall at a few places with heavy rainfall at isolated places over the southern parts of Coastal Tamil Nadu. Rainfall is forecast to reduce thereafter.

A weather alert issued by private forecaster Skymet Weather has forecast spells of rain and thundershowers with gusty winds and isolated heavy spells likely at many places in Tamil Nadu in the districts of Ariyalur, Chennai, Coimbatore, Cuddalore, Dharmapuri, Dindigul, Erode, Kancheepuram, Kanyakumari, Karur, Krishnagiri, Madurai, Nagapattinam, Namakkal, Perambalur, Pudukkottai, Ramanathapuram, Salem, Sivaganga, Thanjavur, Theni, The Nilgiris, Thiruvallur, Thiruvarur, Thoothukudi, Tiruchirappalli, Tirunelveli, Tiruppur, Tiruvannamalai, Vellore, Viluppuram and Virudhunagar districts of Tamil Nadu early into Tuesday morning.

Movement of convergence zone

According to the IMD, Coastal and South Interior Karnataka, too, would witness light to moderate rainfall at most places and heavy rainfall at isolated places until Tuesday.

The US National Centres for Environmental Prediction-Global Ensemble Forecast System (NCEP-GEFS) continues to suggest fresh easterly wave activity to begin in the next four to five days over the Bay of Bengal but aiming mostly at Sri Lanka and the southern coast of Tamil Nadu.

This is also in line with the seasonal movement of the InterTropical Convergence Zone (ITCZ) into the Southern Hemisphere towards the end of the North-East monsoon.

The ITCZ appears as a band of clouds consisting of showers, with occasional thunderstorms, that encircles the globe near the equator. The solid band of clouds may extend for many hundreds of kilometres, and is sometimes broken into smaller line segments.

The ITCZ follows the movement of the sun, and so its position varies seasonally. It moves North in the Northern Hemisphere summer and South in the Northern Hemisphere winter. This is why the ITCZ is considered responsible for the wet and dry seasons in the tropics.

Wind warning issued

Meanwhile, the IMD has also issued a high wind warning for fishermen who have been advised not to venture into the sea in these areas.

Monday: Squally weather (wind speed of 40-50 km/hr) gusting to 60 km/hr) may prevail over the South-West Arabian Sea (West of Lakshadweep)l; Lakshadweep area and adjoining South-East Arabian Sea along and off the Kerala and Karnataka coasts; the Comorin-Maldives areas; the Gulf of Mannar; and South-West Bay of Bengal along and off the South Tamil Nadu coast.

Tuesday: Squally weather (wind speed of 50-60 km/hr gusting to 70 km/hr) may prevail over the South-West Arabian Sea and along and off the Somalia coast; squally weather (wind speed of 40-50 km/hr gusting to 60 km/hr) over the Lakshadweep area; the South-East and adjoining East-Central Arabian Sea; and along and off the Karnataka coast.

Wednesday: Gale wind speeds reaching 60-70 km/hr gusting to 80 km/hr may prevail over the South-West Arabian Sea and along and off the Somalia coast; squally weather (wind speed of 40-50 km/hr gusting to 60 km/hr) may prevail over the East-Central Arabian Sea and along and off Maharashtra coast.

Thursday and Friday: Gale wind speeds reaching 70-80 km/hr gusting to 90 km/hr over the South-West Arabian Sea and along and off the Somalia coast followed by gale wind speeds of 60-70 km/hr gusting to 80 km/hr.

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