India Meteorological Department (IMD) on Thursday evening altered the outlook for cyclone Fengal over south-west Bay of Bengal saying there is a possibility of ‘marginal intensification of the parent deep depression into a cyclone’ during a small window available between Thursday evening and Friday morning. 

The minimal cyclone will feature wind speeds of 65-75 km/hr gusting to 85 km/hr over the seas even as the deep depression struggled to move past Sri Lankan waters on Thursday. It had slowed down due to twin impact from toying with Sri Lankan coast and high vertical wind shear. A western disturbance with strong westerlies has not allowed the storm tower to hold properly. 

Landfall on Saturday 

On Thursday morning, the laggard deep depression was located about 110 km east-northeast of Trincomalee in Sri Lanka; 310 km south-east of Nagapattinam; 410 km south-east of Puducherry; and 480 km south-southeast of Chennai. After skirting Sri Lanka, it will move north-northwest to cross north Tamil Nadu-Puducherry coasts between Karaikal and Mahabalipuram on Saturday morning, weakened from a cyclone back as a deep depression, with a wind speeds of 50-60 km/hr gusting to 70 km/hr.

Wind shear, cooler seas

The shear has sent a bulk of cloud bands to south and adjoining central Bay and neighbourhood spanning Sri Lanka, Palk Strait, Gulf of Mannar, coastal Tamil Nadu and coastal Andhra Pradesh. Continuous rain has cooled down a side of the deep depression while sea-surface temperatures are cooler towards coast. Still, the system will have a small window for opportunity to ramp up.

As it travels closer to coast, land interaction, high wind shear, lower sea-surface temperatures and cold dry air incursion from mainland India may lead to weakening of cyclone back into a deep depression, an IMD analysis said. On Thursday, the incoming western disturbance was spotted over western Iran on way to Afghanistan and Pakistan, before reaching North-West India. 

Rain outlook for Tamil Nadu

The IMD has predicted isolated heavy to very heavy rain over north Tamil Nadu with extremely heavy falls at isolated places on Friday and Saturday. It will be heavy to very heavy with extremely heavy falls over south Andhra Pradesh & Yanam and Rayalaseema on Friday. Heavy to very heavy rain is likely over Kerala & Mahe and South Interior Karnataka on Saturday and Sunday; Coastal Andhra Pradesh & Yanam and Rayalaseema on Saturday; and Tamil Nadu, Puducherry & Karaikal on Sunday. 

Heavy rain is likely over Kerala & Mahe and South Interior Karnataka on Friday and Monday; Andaman & Nicobar Islands on Saturday; and Lakshadweep Monday and Tuesday. Meanwhile, global models signalled initiation of a cyclonic circulation over the south-east Bay early next week and propulsion of a rain-friendly easterly wave directed at south Tamil Nadu and Sri Lanka.