FOR WEB + PRINT
The ‘well-marked’ low-pressure area over the North Andaman Sea has intensified into a depression and lay over the South-East and adjoining East-Central Bay of Bengal, to the West of Andaman Islands, India Meteorological Department (IMD) said in a pre-cyclone watch issued on Saturday evening. The depression was located 110 km North-North-West of Port Blair; 1,460 km South-South-East of Sagar Island (South of Kolkata); and 1,130 km South-South-East of Barisal (Bangladesh).
Severe cyclone likely
The depression is likely to move to the North-West and intensify further into a deep depression (a step lower than a cyclone) over East-Central and adjoining South-East Bay by Sunday morning. Subsequently, it is expected to recurve gradually to the North-North-East (towards West Bengal-Bangladesh) and intensify into a cyclone ‘Sitrang” by the morning of Diwali on Monday. Wind speed projections hint ‘Sitrang’ could become a severe cyclone by Tuesday.
The cyclone is expected to move North-North-East and cross the Bangladesh coast between Tinkona Island and Sandwip by Tuesday morning, after skirting Odisha and West Bengal coasts. Sea-surface temperatures continue to be warmest (beyond 30 degrees Celsius) along the Bangladesh coast which helps the storm to ravenously feed on moisture generated by enhanced evaporation and help build the storm tower to greater heights.
Wind shears values
Wind shear values (change in speed and direction with height) are high over this area and show a tendency to grow further, which can shear the storm head from the top, weakening its structure. Meanwhile on Saturday, with the depression having moved away, winds over Tamil Nadu and the rest of the South Peninsula have changed direction to being dry after moisture mopped up from the Bay got directed into the storm system.
The rain belt is along moving along with it towards West Bengal, Bangladesh and the North-Eastern States of India. Satellite pictures showed parcels of angry and tall thunderclouds invading almost the entire Bay as they waited to fall in line to set up the cyclone. They would trigger squally winds with speeds of 55-65 km/hr gusting to 75 km/hr over the central parts of the Bay from Sunday morning. Wind speeds would gradually increase to 65-75 km/hr gusting to 85 km/hr from the evening.
High winds forecast
Squally winds with speeds reaching 35-45 km/hr and gusting to 55 km/hr are likely along and off Odisha and West Bengal coasts and the Andaman Islands and adjoining North Andaman Sea. The sea condition will remain ‘very rough’ (wave heights of 13-20 ft) over the Central Bay in the morning. It would become ‘high’ (20-30 ft) from the evening while being ‘rough’ (8-13 ft) along and off the Odisha-West Bengal-Bangladesh coasts.
Stormy over East, North-East
Fairly widespread rain with isolated heavy falls is likely for Odisha and the plains of West Bengal on Monday and Tuesday. Isolated very heavy rainfall is also likely over West Bengal. Fairly widespread to widespread light to moderate rain with isolated heavy falls, thunderstorms and lightning are likely over Arunachal Pradesh. Similar weather will pan out in Assam and Meghalaya from Monday to Wednesday, and over Mizoram and Tripura from Sunday to Wednesday. Isolated very heavy rain may lash Arunachal Pradesh on Monday and Tuesday; and Assam, Meghalaya, Mizoram and Tripura on Monday. Isolated extremely heavy falls are likely over South Assam, Meghalaya, Mizoram and Tripura on Tuesday.