- A cyclone is taking shape in the North Indian Ocean region. The Bay of Bengal will see its second Severe Cyclone of the year, after Super Cyclone Amphan formed in May. It is likely to hit Tamil Nadu coast by midweek. The next three days shall see extremely heavy rain, strong winds along with highly rough sea conditions.
Q. Why are Tamil Nadu and Puducherry on ‘red’ alert?
- The India Meteorological Department (IMD) has forecast the development of a cyclone in the Southwest region of the Bay of Bengal, off Tamil Nadu coast. After cyclone Gaja in 2018, this will be the second cyclone to cross Tamil Nadu in the last two years.
- As of 5.30 am Tuesday, the cyclone was located 410 km east-southeast of Puducherry and 450 km southeast of Chennai.
- The Met department has said that it will strengthen into a cyclone. Once intensified, it would acquire its name ‘Nivar’, proposed by Iran.
Q. When will the cyclone develop, what would be its intensity?
- The depression will intensify into a cyclone sometime on Tuesday(24th NOV ) At this stage, the wind speed will range between 70 to 80 km/hr gusting to 90km/hr.
- The cyclone will further gain strength into a Severe Cyclone category (90 to 100 km/hr gusting to 110 km/hr) by Wednesday.
- It is expected to hit Tamil Nadu coast on Wednesday afternoon. The projected track indicates its landwards crossing between Karaikal and Mamallapuram near Puducherry as a severe cyclonic storm (100 to 110 km/ hr gusting to 120 km/hr.
Q. What adverse weather can this cyclone cause for the east coast?
- The maximum hazard due to this cyclone will be caused to Tamil Nadu. Extreme weather, here, would occur both on Tuesday and Wednesday. In association with development of the severe cyclonic storm, sea conditions in the west-southwest regions of the Bay of Bengal have turned rough to extremely rough and remain at its most unfavourable condition .
- With extremely heavy rain — of the order of 20cm or more, forecast on Wednesday, the IMD has placed Tamil Nadu under ‘red’ (take action) alert. Northern districts, here, could experience rainfall more than 24 cm on the day.
- Heavy rain (64 to 115mm) is also forecast over Rayalaseema, Telangana, coastal Andhra Pradesh, Tamil Nadu, Puducherry, Karaikal and south interior Karnataka during November 24-26.
- Southern Chhattisgarh and Odisha, too, will come under the influence of the cyclone with some rainfall activity likely on November 26 and 27.
- Since Monday, squally winds prevailed in the sea and it is set to gain momentum during the next three days.
- On Tuesday, winds with speeds 65 to 75 km/hr gusting to 85 km/hr would prevail off Tamil Nadu coast. As the cyclone would inch closer to the coast and enter the ‘severe’ category, winds with speeds 100 to 110 km/ hr gusting to 120 km/hr is forecast over north Tamil Nadu, Puducherry and Karaikal. Such strong winds are expected for at least 12 hours on Wednesday.
- At the time of the cyclone crossing over to the land, storm surge with tidal waves up to one metre in height above the astronomical tide, is expected. This could lead to inundation of low-lying areas. Most of the storm surge would be experienced along the coastal areas between Puducherry and Chennai.
- On Wednesday, the sea condition would be high to very highly unfavourable, triggering sea waves up to 10 metres high.
Q. Which areas will be affected by the cyclone?
- Northern districts of Tamil Nadu will face the maximum hazard. On Tuesday, heavy rain is predicted for Pudukottai, Thanjavur, Tiruvarur, Karaikal, Nagapattinam, Cuddalore, Ariyalur and Perambu. On the day of cyclone crossing the land, districts like Puducherry, Kallakurchi, Kadalur, Villupuram, Tiruvannamalai, Chengalpattu and Karaikal could record extremely heavy rain.
- Coastal Andhra Pradesh, Nellore and Chittoor districts of Rayalaseema, Telangana, south interior Karnataka will also receive rainfall due to this cyclone between November 24 – 26.
Q. What damage is expected in Tamil Nadu?
- The IMD has suggested complete suspension of fishing activity in the west-southwest regions of the Bay of Bengal till November 25. Fishermen have been advised to not venture into the sea during the next three days.
- Temporary houses and huts could suffer damage. Power and communication lines, trees could be uprooted. Standing crops could be hit due to the saline water carried landwards by the cyclone.
Q. What are Cyclones?
- There are two types of cyclones:
- Tropical cyclones; and
- Extra Tropical cyclones (also called Temperate cyclones or middle latitude cyclones or Frontal cyclones or Wave Cyclones).
- The World Meteorological Organisation uses the term 'Tropical Cyclone’ to cover weather systems in which winds exceed ‘Gale Force’ (minimum of 63 km per hour).
- Tropical cyclones develop in the region between the Tropics of Capricorn and Cancer. They are large-scale weather systems developing over tropical or subtropical waters, where they get organized into surface wind circulation.
- Extra tropical cyclones occur in temperate zones and high latitude regions, though they are known to originate in the Polar Regions.
Q. What is Tropical Cyclones?
- Tropical cyclones are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges.
- Tropical Cyclones are one of the most devastating natural calamities in the world.
- Tropical cyclones originate and intensify over warm tropical oceans. The conditions favourable for the formation and intensification of tropical storms are:
- Large sea surface with temperature higher than 27° C.
- Presence of the Coriolis force.
- Small variations in the vertical wind speed.
- A pre-existing weak low- pressure area or low-level-cyclonic circulation.
- Upper divergence above the sea level system.
Q. What are Extratropical Cyclone?
- Extratropical cyclones are referred to as mid-latitude depressions, temperate cyclones, frontal depressions and wave cyclones.