Tropical Storm Bertha formed along the U.S. Gulf Coast on Monday evening. Photo courtesy NOAA

July 21 (UPI) -- Tropical Storm Bertha strengthened just off the coast of the Florida Panhandle on Tuesday as it made its way west, the National Hurricane Center said.

The storm, which isn't expected to become a hurricane before fizzling out, formed Monday night.

The epicenter of the storm was located about 70 miles south-southwest of Panama City, Fla., and 145 miles southeast of Mobile, Ala., the NHC said in its 10 a.m. CDT update. The storm was traveling north-northwest at 3 mph and had maximum sustained winds of 60 mph.

Winds must reach at least 74 mph for a storm to be considered a hurricane.