'Extremely Severe Cyclonic Storm' Amphan Barrels Towards India, Bangladesh

India and Bangladesh are facing "catastrophic storm surge potential" from Cyclone Amphan as the major storm triggers mass evacuations a day before it's expected to make landfall on the Bengal coast.

The India Meteorological Department classified Amphan on Tuesday as an "extremely severe cyclonic storm" that would likely carry maximum sustained wind speeds of 155-165 kilometers per hour gusting to 185 kmp when the cyclone hits India's West Bengal state and Bangladesh.

The storm has weakened since Monday night when it was recorded as the Bay of Bengal's strongest ever storm, packing sustained winds of 270 kilometers per hour (165 miles per hours). Meteorologist Eric Holthaus warned Tuesday morning that Amphan could still bring major damage.

"This storm is deadly serious," Holthaus tweeted.

"Amphan will likely make landfall as a Category 2 equivalent, perhaps a Category 3," meteorologist Bob Henson wrote Tuesday. "Nevertheless, a major storm surge is almost certain given the storm's trajectory and the geography of the Bay of Bengal."

Henson explained further:

Although Amphan's high winds will wreak havoc, and its torrential rainfall will cause inland flooding--a major concern in itself, given the storm's vast envelope of moisture--the most serious threat posed by Amphan is potentially catastrophic storm surge. Even if Amphan's top winds weaken further, the storm surge threat will likely remain extreme. Amphan is a large cyclone that is already pushing a tremendous amount of water northward into the Bay of Bengal, which exerts a funneling effect on northward-moving cyclones. There is a great deal of momentum in the water pushed by large, powerful storms when their peak winds weaken but their overall wind fields expand, as evidenced by 2008's Hurricane Ike in Texas and 2012's Hurricane Sandy in New Jersey and New York.

Compounding the difficulties of keeping people safe during evacuations is the ongoing threat of Covid-19. From BBC News:

This time round there is the coronavirus pandemic to contend with too--social distancing protocols to curb the spread of infection mean more shelters are needed, and thousands of migrant workers displaced by lockdown restrictions in India are on the move, many heading by foot to coastal villages.

Preparations to shelter millions in Bangladesh are already underway, the Associated Pressreports:

Authorities in Bangladesh warned that the cyclone could flood vast swaths of southwestern and southern areas. Junior Minister for Disaster Management and Relief Enamur Rahman said evacuations had begun in the southwest, where residents of Satkhira district, which was devastated by a 2009 cyclone, will be moved to shelters.

Rahman said he ordered local authorities to prepare thousands of shelters and makeshift structures to protect more than 5 million people before the cyclone crosses the region.

Amphan is the second ever recorded super cyclone to hit the Bay of Bengal. The other, the Odisha Cyclone, struck in 1999.