Cyclone Michaung over west-central and coastal south Andhra Pradesh has intensified into a ‘severe’ cyclonic storm, and is expected to make landfall near the state’s Bapatla district on the morning of December 5, said an official on Monday (December 4). The storm has led to heavy rainfall in several parts of Andhra Pradesh, in most parts of Tamil Nadu, and southern Odisha.
Here is a look at cyclone-prone areas in India, what fuels tropical cyclones, why Michaung is unique, and how much devastation it can cause.
Why is Cyclone Michaung unique?
Due to unfavourable ocean conditions, storms developing over the North Indian Ocean during December don’t attain destructive intensities. Therefore, cyclones of high intensity are uncommon in December.
The IMD had,initially, predicted Michaung to remain as a cyclone till it crossed the Andhra Pradesh coast. But on December 3, the Met department upgraded Michaung to intensify into a ‘severe’ storm.
Such intensification observed in a December cyclone was unique, the IMD said.
It is above the normal value of the heat index, recorded off the south Andhra Pradesh coast, that was favouring Michaung to strengthen (scroll down for more details), IMD officials said.
Where is Michaung headed?
Cyclone Michaung is expected to travel parallel and close to the south Andhra Pradesh coast till late Monday. Later, it will cross the south Andhra Pradesh coast between Nellore and Machilipatnam, close to Bapatla, sometime during forenoon hours on Tuesday.
The IMD has warned of very heavy to extremely heavy rain (115 to 200mm and above) over Godavari, Krishna, Bapatla, Guntur, Srikakulam, Palnadu, Dr BR Ambedkar Konaseema, Yanam, Kakinada, Anakapalli, Vishakapatnam, Vizhianagaram, Kurnool, YSR districts of Andhra Pradesh on Tuesday and Wednesday.
What is the potential threat from Cyclone Michaung?
Cyclone Michaung is expected to majorly cause wide-scale crop damage in Andhra Pradesh. Paddy, pineapple and other standing crops, that are nearing harvest, could be hit due to the unseasonal extremely heavy rainfall (over 200mm in 24 hours) during the next two days. Strong winds with speeds 90-100 km/hr gusting to 110 km/hr, expected during the cyclone’s landfall around Tuesday afternoon, could damage mature crops.
Storm surge and tidal waves up to 1.5 metres are predicted as the cyclone nears the coast till landfall. IMD’s flash flood alert has warned of likely inundation till Tuesday in the low lying areas of Rayalaseema, Yanam, coastal Andhra Pradesh and Karaikal.
Even after the cyclone crosses the Andhra coast, the system is expected to continue to move northwest wards towards southern Odisha. Here, the IMD has issued an ‘orange’ alert ahead of heavy rainfall on Tuesday and Wednesday.
How cyclone-prone is India?
Flanked by sea on three sides, India’s east and west coasts are affected by cyclones, annually.
Climatologically, five cyclones developed in the North Indian Ocean basin — comprising the Bay of Bengal and the Arabian Sea. Of these, an average of four cyclones develop over the Bay of Bengal and one over the Arabian Sea. This basin is most prone to cyclone development during the pre-monsoon season (April – June) and post-monsoon season (October – December) months.
Due to favourable ocean conditions, it has been observed that cyclones formed in May and November usually reach higher intensities than storms formed in the remaining months.
West Bengal, Odisha, Andhra Pradesh, Tamil Nadu, Gujarat and Maharashtra are the most to be affected by cyclones.
Even though cyclone development in the Arabian Sea may be fewer than in the Bay of Bengal, the storms here touch higher intensities and carry the potential to cause wide-scale damage.
What factors influence a tropical cyclone?
Tropical cyclones are fueled by ocean heat. In addition to other factors, warm oceans can contribute to the cyclone’s rapid intensification while at sea. Ocean water temperature measuring 26 degrees Celsius or above, prevailing at depths between 50 – 100 metres, makes it conducive for cyclogenesis.
Another important factor that influences the cyclone genesis, intensification and propagation, is the value of Tropical Cyclone Heat Potential. It is the primary energy supplier to the cyclone through the upward latent heat fluxes.
Cyclone intensification is a highly complex process influenced by a combination of different favourable atmospheric conditions such as the boundary layers, barotropic instability, wind shear, convection, Rossby wave, upper ocean circulation and air-sea interaction.