At a Glance

Tropical Cyclone Amphan made landfall Wednesday near the border between India and Bangladesh.Major storm-surge flooding was expected near and east of where Amphan crossed the coast.Damaging winds and flooding rainfall were also significant threats, including for Kolkata.Amphan's peak intensity was a Category 5 on Monday.

Tropical Cyclone Amphan made landfall Wednesday near the India and Bangladesh border with a major storm surge, high winds and flooding rainfall.

(NEWS: Tropical Cyclone Amphan Turns Deadly)

Amphan's center crossed the coast in far eastern India just to the south of Kolkata Wednesday afternoon (local time) with maximum sustained winds equivalent in strength to a hurricane.

High winds spread inland over eastern India, including Kolkata, where power outages were reported. Winds gusted to 55 mph at Kolkata's airport before the weather observation stopped reporting.

The tropical cyclone also brought strong winds and heavy rain to the Indian state of Odisha. Winds gusted to 66 mph at Paradeep, with a 24-hour rainfall total of 8.19 inches as of early Wednesday morning, according to the India Meteorological Department (IMD).

Amphan's large size and previous extreme intensity resulted in an immense amount of water being pushed northward through the Bay of Bengal. That water funneled into the river deltas near the border between India and Bangladesh.

The coastline of the northern Bay of Bengal is extremely prone to storm-surge flooding. You can read more about why that is at the bottom of this article.

Amphan's Extreme Category 5 Intensification

Amphan's rapid strengthening made history for the North Indian Ocean Basin earlier this week.

Maximum sustained winds in Amphan increased from 75 mph to 160 mph in just 24 hours from Sunday afternoon into Monday afternoon India time. That means it strengthened from a equivalent on the Saffir-Simpson Hurricane Wind Scale.

Amphan's winds later increased to 165 mph, which tied it with Gonu (2007) for the strongest tropical cyclone on record in the North Indian Ocean dating to 1972, according to , a tropical scientist at Colorado State University.

Tropical Cyclone History of the Bay of Bengal

Last year, Cyclone Fani hit Odisha in May, killing more than 70 people in Odisha and West Bengal. Fani was also an Extremely Severe Cyclonic Storm with maximum sustained wind speeds of 135 mph.

(This section is from Weather Underground's Category 6 blog)

The triangular shape of the Bay of Bengal acts to funnel storm-surge waters into Bangladesh, and the very shallow bottom of the bay allows the surge to pile up to very high heights. Thus, there is good reason to be concerned when a hurricane-strength tropical cyclone gets loose in the Bay of Bengal: Twenty-six of the have been Bay of Bengal storms, as seen in Weather Underground's list of the 35 Deadliest Tropical Cyclones in World History (note that since this list was published, research has found that the 1882 Great Bombay Cyclone, which supposedly killed 100,000 people, in reality never occurred). The big killer in all of the most deadly Bay of Bengal cyclones was the storm surge.

During the past two centuries, 42% of the Earth's tropical cyclone-associated deaths have occurred in Bangladesh and 27% have occurred in India (Nicholls et al., 1995). The deadliest storm in world history, the 1970 Bhola Cyclone of 1970, killed an estimated 300,000 to 500,000 when it made landfall in Bangladesh on Nov. 12, bringing a storm surge estimated at up to 10.4 meters (34 feet) to the coast.

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