Tropical Cyclone Roanu made landfall just after midday Saturday northwest of Chittagong, Bangladesh, and still poses a threat of dangerous flooding in parts of eastern India, Bangladesh, and Myanmar into the weekend.
The India Meteorological Department estimated Roanu's maximum sustained winds were 50-55 mph (80-90 kph) at landfall, with gusts to near 70 mph (110 kph), while the U.S. Joint Typhoon Warning Center estimate was slightly higher at 60-65 mph (55 knots).
The Bangladesh Meteorological Department warned of a storm surge of 4-5 feet above normal tide levels along the coast of Bangladesh arond the time of landfall. Typically higher tides around the monthly full moon were only expected to aggravate the coastal flooding.
Roanu has already turned deadly, with wind damage reported in the city of Chittagong, coastal embankments destroyed, and at least one landslide triggered from heavy rain.
Roanu, and clusters of thunderstorms ahead of the cyclone, have wrung out some impressive rainfall totals in India and Bangladesh.
In general, the rainfall potential of a tropical cyclone is not a function of its intensity (i.e. maximum sustained winds), but rather its forward speed.
Some of the most extreme rainfall events worldwide have occurred when tropical cyclones, in some cases as weak as depressions or even remnant lows, move slowly, or stall.
After dumping over a foot of rain, triggering destructive mudslides in Sri Lanka earlier in the week, an area of low pressure consolidated enough convection near its center to be deemed a tropical cyclone just off the coast of India's Andhra Pradesh state northeast of the city of Chennai Wednesday.
Convection burst near the center of Roanu early Friday as its center meandered near the eastern coast of India, spreading heavy rain through parts of Andhra Pradesh, Odisha, and West Bengal states.
Despite the convective burst, thanks to wind shear, the change in wind speed and/or direction with height, Roanu was not able to strengthen much as it tracked generally northeast toward the coast of Bangladesh Saturday.
The Bay of Bengal has a notorious history for the world's deadliest tropical cyclones, owing to both population density of low-lying areas near the coast and the shallow northern end of the Bay of Bengal, funneling storm surge into Bangladesh, in particular.
In early May 2008, Cyclone Nargis slammed into southern Myanmar, driving a storm surge into the country's Irrawaddy Delta, claiming over 138,000 lives in the country's worst natural disaster.
In 2015, Tropical Cyclone Komen combined with the normal wet phase of the Asian monsoon to dump over 3 feet (1 meter) of rain to parts of eastern Bangladesh.
The resulting flooding and mudslides claimed at least 200 lives and destroyed 55,000 homes.