Cyclone Arnab: Why It Hit So Hard, and How Cyclones Form
Cyclone Arnab killed at least three people and forced over 180,000 evacuations in Andhra Pradesh and Odisha this week. Here is how cyclones form and how India tracks them.
Cyclone Arnab made landfall on the Andhra Pradesh and Yanam coast early on 28 October 2026, near Narsapur in West Godavari district. The India Meteorological Department (IMD) classed it a "very severe cyclonic storm," with sustained winds of 125-135 kmph and gusts up to 150 kmph. At least three people died, more than 180,000 people were evacuated across Andhra Pradesh and Odisha, and about 200,000 acres of cropland were flooded.
What actually happened
Authorities moved more than 84,000 people to shelters in Andhra Pradesh and over 30,000 in Odisha before landfall. In Andhra Pradesh, three deaths were reported, two of them from electrocution after live wires snapped in the wind, and 31 houses were damaged. Odisha reported uprooted trees but no major damage. The IMD also warned of heavy to extremely heavy rainfall in coastal Andhra Pradesh and southern Odisha, with flooding and landslide risk in vulnerable districts. After landfall, the storm weakened into a "severe cyclonic storm" and moved north-northwest, losing strength as it moved inland.
Meteorologists quoted by The Associated Press said unusually high temperatures across the Bay of Bengal, plus heat already stored below the surface, let the storm strengthen quickly. A warmer atmosphere can also hold more moisture, which raises the risk of intense rainfall, according to K.J. Ramesh, a former IMD director general.
How a cyclone actually forms
According to the US National Oceanic and Atmospheric Administration (NOAA), a tropical cyclone needs a few specific ingredients to form:
- Warm ocean water, at least 26.5°C down to about 50 metres deep. This warm water is the storm's fuel.
- A starting disturbance, usually a low-pressure area that already has some shower or thunderstorm activity.
- Low wind shear, meaning winds at different heights of the atmosphere are not blowing too differently. Strong shear tears a developing storm apart.
When these line up, warm, moist air rises off the ocean into the disturbance, which lowers the pressure near the surface and pulls in more air. That air rises and cools, forming thunderstorm clouds. As the water vapour in those clouds condenses into droplets, it releases heat, which fuels the storm further. This cycle can repeat and intensify for days, as long as the storm stays over warm water.
How India classifies and names cyclones
The IMD tracks storms over the North Indian Ocean using maximum sustained wind speed, averaged over three minutes, not gusts:
Depression
Winds of 31-49 kmph. A closed low-pressure circulation has formed.
Cyclonic storm
Winds of 62-88 kmph. The system is developed enough to get a name.
Severe cyclonic storm
Winds of 89-117 kmph. Strong enough to cause real damage.
Very severe cyclonic storm
Winds of 118-167 kmph. This was Arnab's category at landfall.
Extremely severe cyclonic storm
Winds of 168-221 kmph. Large-scale destruction is likely.
Super cyclonic storm
Winds of 222 kmph or more. The most catastrophic category.
Because the scale uses 3-minute sustained winds, a storm can produce a much higher gust than its category suggests. That is one reason gust speed and category are not the same thing.
What most people miss
- The category can drop fast after landfall, but heavy rain and flooding often remain the bigger danger for a day or two after the wind dies down, as happened with Arnab's inland flooding.
- Gusts and sustained winds are different numbers. A storm's official category is based on the lower, sustained figure, so reported gusts can sound far more dramatic than the classification.
- Downed power lines kill more people than most expect in the hours after a cyclone passes; two of Arnab's three confirmed deaths were from electrocution, not wind or flooding directly.
- Warmer seas do not necessarily mean more cyclones, but research suggests they can make the ones that do form wetter and more intense, which is why rainfall warnings matter as much as wind warnings.
Sources
- Business Today: Cyclone Arnab landfall – satellite images show storm covering almost half of India
- ABC News (AP wire): India's Cyclone Arnab brings high toll of extreme weather into focus
- NOAA Ocean Service: How do hurricanes form?
- OdishaTV: Cyclone Montha turns into severe cyclonic storm – know how IMD classifies storms based on intensity
