Cyclone Fani, packing winds of nearly 177km/h, is set to slam northeastern India later this week, bringing with it destructive winds, rain totals topping a foot and a potentially devastating storm surge.

The India Meteorological Department is calling Fani a "very severe cyclonic storm," expecting it to intensify into an "extremely severe cyclonic storm."

Fani is meandering north-northwest at 20km/h, continuing to gain strength over the bath-warm seas in the Bay of Bengal. Water temperatures there range from the mid- to upper 20sC, a few degrees above normal, which supports further intensification.

The Joint Typhoon Warning Centre predicts that Fani will make landfall on early Friday local time with peak winds over 210km/h, equivalent to a Category 4 hurricane.

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The storm is expected to hit the heavily populated state of Odisha. Odisha, with a population exceeding 46 million, is known for its rich history and thousands of temples.

The India Meteorological Department has hoisted a wind warning for Odisha, anticipating winds of 200km/h or greater along the immediate coastline. It is forecasting the "total destruction of thatched houses" and "extensive damage" to other structures.

This will pose major problems for neighbourhoods near the beach in Puri, a city of 200,000 people, where a 1.5m storm surge (or rise in water above normally dry land) is also expected.

As the storm is still roughly 72 hours from landfall, its exact track remains uncertain. But if the eye of the storm tracks just west of Puri, the city of 200,000 could be ground zero for the worst of the wind and surge.

The bulk of Puri is built up high enough above sea level that those more than a few hundred metres inland will be immune to the ferocious waves.

Farther north, it's a different story. Tens of thousands of people from the Mahanadi River Delta to Kalibhanja Diha Island live less than 3m above sea level. It could be disastrous for dozens of impoverished rural communities, inundating homes and businesses.

The Indian Government ominously cautioned the "flooding of escape routes" will prevent evacuation if residents wait too long.

Inland, the threat is less from coastal flooding but more due to inland flooding. Rain totals of 20-30cm will fall over a widespread swath that will include Odisha's capital, Bhubaneswar. A heavy-rain warning is in effect for potential "heavy to very heavy rainfall at a few places with isolated extremely heavy rainfall."

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Eastern India is accustomed to monsoonal moisture this time of year, but it isn't equipped to handle a month's worth of precipitation coming down in a few hours. In addition to sparking urban flood concerns in Bhubaneswar proper, excessive runoff could overwhelm the Mahanadi and Kuakhai rivers. That may cause flash flooding along their banks for rural communities surrounding Cuttack and Urali.

It's not just homes that will suffer - the local economy could be severely affected. "Widespread damage to standing crops, plantations, orchards," per forecasts from the India Meteorological Department, could grind local commerce to a halt. The average per capita income in Odisha is less than US$1000 per year.

The storm could also cause serious effects in Bangladesh, pushing a substantial storm surge over its low-lying coast and unloading flood rains.


PREVIOUS CYCLONES

Many of the deadliest recorded cyclones have struck coasts along the Bay of Bengal, which has densely populated, low-lying zones vulnerable to storm surge, flimsy infrastructure, and - in many instances - lack of early storm warnings and evacuation efforts.

A Category 5-equivalent cyclone devastated Odisha in 1999, unleashing a 6m-plus storm surge and 257km/h winds. That storm was blamed for more than 10,000 deaths.

However, when Cyclone Phailin slammed Odisha in October 2013, the toll was not nearly as severe, thanks to improved forecasting and evacuation efforts. Ahead of that storm, 1.2 million people were evacuated. Dozens, rather than thousands, died.