Tropical storm warnings were also issued on the east coast from South Santee River, South Carolina to Sebastian Inlet, Florida. Colin, with top winds of 80 km/h, was 460km west-southwest of Tampa, the hurricane centre said the advisory.
Colin is the third named storm of 2016 and the second in about a week, heralding an early start to the Atlantic hurricane season, which began on June 1. The first storm of the year was Hurricane Alex, which formed in the mid-Atlantic in January. A storm gets a name when its winds reach tropical-storm strength of 62 km/h.
By the time Colin reaches the Atlantic, its winds could peak at 95km/h as it is nudged away from the East Coat by a low pressure system over the eastern part of the country.
While Colin has strengthened some since it first developed on Monday, it is disorganised and facing wind shear, which will probably keep it from getting any stronger, Brown wrote.
"It should be noted that Colin could lose its status as a tropical cyclone while impacts are still occurring along the coast," Brown wrote. "In this case, NHC would anticipate continuing advisories and warnings on the post-tropical cyclone."