Cyclone Arnab formed in the Bay of Bengal on October 23 and intensified into a very severe storm by October 26. It crossed the coast between Bapatla and Visakhapatnam at 1 am on Wednesday. The storm brought heavy rain to coastal Andhra Pradesh and Odisha, causing significant damage across the region.
How did Cyclone Arnab form and intensify?
Cyclone Arnab is the first cyclone to form in 2026 in the North Indian Ocean basin, which comprises the Bay of Bengal and the Arabian Sea.
It started as a low-pressure system in the southeast Bay of Bengal on October 23, before intensifying into Cyclone Arnab by October 26.
The weather system then rapidly intensified into a “severe” cyclone and later a “very severe” category storm — associated with wind speeds ranging from 125 to 135 kmph.
Cyclone Arnab’s movement towards the land was faster than originally forecast by the IMD, which, late Tuesday night, advanced its landfall forecast from forenoon to the early hours of Wednesday.
Arnab’s landfall commenced at around 1 am on Wednesday. It crossed the coast between Bapatla and Visakhapatnam with wind speeds equivalent to a “very severe” cyclone. At the time of landfall — the process when the cyclone’s “eye” (or centre) crosses from the sea over to the landmass — it had wind speeds of 125-135 kmph gusting to 140 kmph. Cyclones wreak the most damage at the time of landfall.
Usually, storms lose steam upon landfall as they run into the landmass and other obstacles. But that has not been the case with Cyclone Arnab. It maintained the same intensity for at least six hours even after landfall before relatively weakening into a “severe” cyclonic storm.
According to the IMD, Cyclone Arnab remained stationary over regions close to Narsapur (Andhra Pradesh) and Yanam (Puducherry) since 4 am, thereby slowing the landfall process. Normally, cyclone landfall can take up to six hours or more to complete and is dependent on the speed and size of the cyclone.
Heavy rainfall has battered parts of coastal Andhra Pradesh and Odisha since Tuesday. Visakhapatnam recorded 217 mm of rain, Kalingapatam 147 mm, Tuni 123 mm, Kakinada 118 mm, Machilipatanam 115 mm and Gopalpur 94 mm.
El Niño effect on cyclones
Along India’s east coast, coastal districts in Odisha and West Bengal are the most prone to cyclones that develop in the Bay of Bengal. In comparison, few cyclones affect the Andhra Pradesh coast and even fewer hit the Tamil Nadu coast.
This is linked to where a cyclone is formed — it starts as a low-pressure system and intensifies into a depression, a deep depression, a cyclonic storm, and beyond — and the path it takes.
In 2026, the El Niño phenomenon — the abnormal warming of surface waters in the equatorial and central Pacific Ocean — is intensifying rapidly. It can alter rainfall patterns and spike temperatures.
El Niño also affects global wind patterns, causing unusual warming in regions such as the North Indian Ocean.
As the southwest monsoon weakens, the monsoon trough — a band of low pressure that shifts north and south, bringing rainfall to different parts of India — moves southwards. During El Niño years, warmer oceans can further change wind patterns and air pressure near the equator.
During El Niño years, tropical cyclones in the North Indian Ocean tend to form closer to the equator. As a result, they are more likely to move towards Andhra Pradesh and Tamil Nadu than Odisha and West Bengal, IMD chief Mrutyunjay Mohapatra had explained earlier.
2014, another El Niño year, saw Cyclone Hudhud barrel towards the Andhra Pradesh coast.
As a result, cyclones that form under these conditions not only intensify rapidly but also move faster, as seen in the case of Cyclone Arnab.
Tropical cyclones’ fuel
From July to September, sea surface temperatures in the equatorial Pacific’s Niño 3.4 region — the region that is used to measure El Niño’s intensity — were 2 to 2.8 degrees Celsius above normal, indicating warm oceans.
Ocean temperatures of 26 degrees Celsius or above, at depths between 50 and 100 metres, are conducive for the formation of cyclones. Tropical cyclones are fuelled by ocean heat, and warm oceans can contribute to the cyclone’s rapid intensification while at sea.
Cyclone Arnab strengthened to its highest intensity as a “very severe” cyclone over a single day.
Cyclone intensification is a highly complex process influenced by a combination of different favorable atmospheric conditions, such as the boundary layers, wind shear, convection, upper ocean circulation and air-sea interaction.
Arnab’s path and impact
Heavy rainfall (64-115mm in 24 hours) will continue to batter northern districts of Andhra Pradesh and south Odisha districts coasts till Thursday. Odisha and Andhra Pradesh remain on ‘red’ alert while Chhattisgarh is on ‘orange’ alert on Wednesday.
As Cyclone Arnab will recurve northwards, it will bring very heavy rainfall (115-204mm in 24 hours) over parts of Telangana, Chhattisgarh, Jharkhand, Bihar, Gangetic West Bengal, eastern Madhya Pradesh and eastern Uttar Pradesh, where its weakened remnants are expected to cross during the next two days.