Cyclone Arnab: How a Bay of Bengal Depression Triggered Widespread Flooding Across India
What Is Cyclone Arnab?
Cyclone Arnab began as a deep depression over the Bay of Bengal, tracked closely by the India Meteorological Department using Doppler Weather Radar systems. Despite never intensifying into a full-fledged cyclone in the technical sense, the system carried enough moisture and energy to trigger serious weather disruptions across eastern and central India.
Landfall and Track
The system made landfall along the coast between 5 pm on September 23 and 5 am on September 24, coming ashore between Visakhapatnam and Gopalpur, near Kalingapatnam. From there, it pushed inland, weakening gradually but continuing to dump heavy rain across a wide swath of the country.
State-Wise Impact Summary
State | Key Impact | Alert/Action Taken |
|---|---|---|
Odisha | Very heavy to extremely heavy rainfall in south Odisha; landslide in Gajapati (Paribeta Ghat road); 140 landslide-prone areas flagged | Red warning for Koraput (Sep 23–25); 33 ODRAF teams deployed; schools shut; fishermen advised off the sea until Sep 24 |
Andhra Pradesh | Heavy rain across 129 mandals, extremely heavy in 9; strong winds of 50–70 kmph in the north | Schools/Anganwadi centres closed in Srikakulam |
West Bengal | Heavy rainfall reported as depression tracked inland | Listed among worst-affected states |
Uttar Pradesh | ~50 cities saw intermittent rain; crop damage from gusty winds; waterlogging in fields; Lucknow under cloudy skies | Yellow alert for Nainital, Champawat, Udham Singh Nagar |
Madhya Pradesh | Very heavy rain expected in several districts | Orange alert for 13 districts incl. Jabalpur; heavy rain alert for 16 more |
Sikkim | Landslide in Rimbi village; 20+ houses/quarters swept away | No deaths reported |
Uttarakhand | Heavy rain expected Sep 26 | Under watch as system's tail moved north |
The Damage on the Ground
The human and infrastructural toll became visible quickly. In Gajapati district, Odisha, authorities had already flagged 140 landslide-prone areas, and that risk materialized when a large rock broke loose from a hillside and fell onto a district road. Reports described trees being uprooted, houses damaged, and rainwater entering homes across affected districts.
Further north, the rain's reach turned destructive in Sikkim, where a landslide swept away more than 20 houses and government quarters, though officials reported no deaths from that incident.
How Authorities Responded
State governments moved quickly on preparedness. Odisha deployed dozens of rapid-response disaster teams, closed schools, and advised fishermen not to venture into the sea given rough conditions. In Andhra Pradesh's Srikakulam district, the local collector declared a school holiday. Officials also kept a close watch on water levels in rivers and dams to catch flood risk early.
What Is a Cyclone?
A cyclone is a large-scale system of winds rotating inward around a low-pressure center. It forms when warm, moist air over the ocean rises rapidly, creating an area of lower pressure near the surface. Surrounding air rushes in to fill this gap, and due to the Earth's rotation (the Coriolis effect), this inflowing air starts to spin — counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
How a Cyclone Forms
Warm ocean water (usually above 26–27°C) heats the air above it, causing the air to rise.
As the warm air rises, it cools and condenses into clouds, releasing heat in the process — this released heat fuels the storm further.
Air from surrounding areas rushes in to replace the rising air, and the Coriolis effect makes this inflow spin around a center.
A calm "eye" forms at the center, surrounded by a wall of intense wind and rain called the eyewall.
If conditions remain favorable (warm water, low wind shear), the system strengthens and can grow into a full cyclone.
Types of Cyclones (by Region)
Region | Name Used |
|---|---|
North Indian Ocean (India, Bangladesh) | Cyclone |
Atlantic Ocean, Northeast Pacific | Hurricane |
Northwest Pacific (near Japan, Philippines) | Typhoon |
South Pacific, Indian Ocean (Australia) | Cyclone / Tropical Cyclone |
They're all the same phenomenon — just called by different names depending on where they occur.
Stages of Development
Stage | Wind Speed |
|---|---|
Low-Pressure Area | — |
Depression | Up to 31 km/h |
Deep Depression | 31–49 km/h |
Cyclonic Storm | 62–88 km/h |
Severe Cyclonic Storm | 89–117 km/h |
Very Severe Cyclonic Storm | 118–166 km/h |
Extremely Severe Cyclonic Storm | 167–221 km/h |
Super Cyclonic Storm | 222+ km/h |
Why Cyclones Cause So Much Damage
Strong winds that can uproot trees, damage buildings, and down power lines
Heavy rainfall leading to flooding and landslides, especially in hilly terrain
Storm surge — a sudden rise in sea level that can flood coastal areas
Rough seas, dangerous for fishing and coastal activity
What's Next
Even as Arnab weakened, its tail brought continued rain. Forecasts pointed to heavy rain likely in Uttarakhand on September 26, with Uttar Pradesh and Madhya Pradesh possibly seeing very heavy rain in parts. For residents across the affected belt, the message from disaster authorities has stayed consistent: stay alert to local advisories, avoid low-lying and landslide-prone areas, and don't underestimate a "deep depression" — as Arnab showed, it doesn't need to reach full cyclone strength to cause serious damage.
