Cyclone Fani is the next in a long line of devastating storms to hit India and Bangladesh

Tropical Cyclone Fani, currently a Category 4 storm, is expected to make landfall near the city of Puri on Friday.

The big picture: The Bay of Bengal has a devastating history of deadly storms. The most tragic was the Great Bhola Cyclone in November of 1970 — with an estimated 300k-500k death toll that makes it the deadliest tropical cyclone in history.

Why so many tropical cyclones form in the Bay of Bengal:

• High sea surface temperatures
• High availability of moisture
• Complexes of thunderstorms are frequent from the Indian Monsoon and tropical weather cycles such as the Madden-Julian Oscillation. These can generate cyclones given the right conditions.

Mitigating disaster: Both countries have improved storm preparedness in recent years to decrease death tolls. In Bangladesh, 56,000 volunteers have been enlisted in coastal areas, warnings have been made through loudspeakers and via mobile phone call trees, and hundreds of thousands of pounds of food and supplies have been brought in.

The deadliest tropical cyclones from the Bay of Bengal (via Weather Underground):

1. Great Bhola Cyclone — Bangladesh — 1970 — 300,000-500,000 deaths
2. Hooghly River Cyclone — India and Bangladesh — 1737 — 300,000
3. Coringa — India — 1839 —300,000
4. Backerganj Cyclone — Bangladesh — 1584 — 200,000
5. Great Backerganj Cyclone — Bangladesh — 1876 — 200,000
6. Chittagong — Bangladesh — 1897 — 175,000
7. Cyclone 02B — Bangladesh — 1991 — 138,866
8. Cyclone Nargis — Myanmar — 2008 — 138,366
9. Bangladesh — 1942 — 61,000
10. India — 1935 — 60,000

Why Bay of Bengal storms are so deadly:

• The low-lying coastal areas of both countries are densely populated, raising the specter of human loss when a storm hits.
• The shape of the Bay of Bengal compounds cyclones’ storm surge, often pushing water well inland.