A brief history of the deadliest cyclones in the Bay of Bengal

As the super cyclonic storm Amphan is approaching towards the coastal regions of India and Bangladesh, it reminds us of the tragic history of tropical cyclones formed in the Bay of Bengal. 

Among many other cyclonic storms, the Great Bhola Cyclone remains in the top with a death toll of around 5 lakh. 

On November 11, 1970, this massive cyclone moved into Bangladesh (known as East Pakistan back that time). The devastating storm-surge flooding produced by the storm was estimated at nearly 35 feet high. It washed the whole flat, low-lying areas and did massive destruction throughout the entire reason. 

Pakistan's meteorological service issued warnings but only a few paid heed to that. Most of the residents did not seek any shelter. Many did not even have a shelter or nearby or a way to reach one, according to NOAA's Hurricane Research Division.

The combination of storm surge and a lack of evacuation resulted in a massive death toll, estimated to be 300,000 to 500,000 people, according to a report published by Weather.com in 2019. 

The death toll alone made it the deadliest known tropical cyclone in history. According to the University of Rhode Island, Over 45 percent of the population of 167,000 in the city of Tazumuddin was killed.

Unfortunately, the Great Bhola Cyclone is not the only tropical cyclone resulting in a large death toll. According to the Bangladesh Meteorological Department, 10 tropical cyclones since 1876 have caused 5,000 or more deaths. Four of those cyclones killed 100,000 or more. Most recently, Cyclone Gorky killed nearly 140,000 in 1991.

The Great Backerganj Cyclone of 1876 alone killed nearly 200,000 people.  The cyclone hit the coast of Backerganj (near Meghna estuary) in present-day Barishal. 

Beside Bangladesh, northeastern coast of India, is also prone to cyclonic storms. The deadliest tropical cyclone to hit India in the last few decades was the 1999 Odisha Cyclone, which struck northeastern India in the state of Odisha as a Category 4-equivalent storm with 155-mph winds on October 29, 1999.

Odisha Cyclone, which had been at Category 5-equivalent strength with 160-mph winds and a 912-millibar central pressure shortly before landfall, pushed a storm surge of 26 feet (8 meters) onto the northeastern Indian coast. 

The storm stalled just inland, dumping torrential rainfall on portions of India already saturated from the landfall of Category 4-equivalent Tropical Cyclone 04B just 12 days earlier.

The 1999 Odisha Cyclone killed 9,658 people and caused $2.5 billion in damages (1999 dollars). 

It was India's most expensive and fourth-deadliest tropical cyclone in the past 100 years, according to Bob Henson, meteorologist and climate blogger at Weather Underground.

Cyclone Nargis in 2008 devastated the southern delta region of Myanmar, southeast of Bangladesh, with extreme storm-surge flooding. More than 130,000 people were killed, mostly in neighbouring country Myanmar.

According to Weather.com, several factors that make the Bangladesh coast and portions of the Myanmar and India coasts vulnerable to storm surge are:

• These areas with high death tolls are low in elevation and have high populations because of agriculture in the region. This puts many people at risk if they do not follow warnings to protect themselves or if sufficient shelter is not available.
• The northern end of the Bay of Bengal is shallow and narrow. This creates a funnel for the huge surge from strong tropical cyclones moving north or northeastward into the low-lying land areas.
• High astronomical tides significantly add to the height of the surge if the cyclone is making landfall during high tide. According to the Bangladesh Meteorological Department, this was the case in both the 1970 and 1991 cyclones.
• Areas along the coast have many small inlets that water is forced into by landfalling tropical cyclones, which causes flooding of adjacent land areas.