Tropical Storm Bertha strengthened overnight and had 50 mph winds as of Tuesday, and tropical storm warnings were in effect for the Alabama coast.

A tropical storm swirling in the US Gulf is expected to bring heavy rainfall and a "life-threatening storm surge" to the south-east of the country, according to the National Hurricane Center (NHC).

The tropical storm watch has been issued from the Florida panhandle to the southeast Louisiana coast, including Panama City and Pensacola, Florida; Mobile, Alabama; and Gulfport, Mississippi.