Residents on Florida's Gulf coast filled sandbags, schools closed early and graduation ceremonies were postponed as Gov Rick Scott declared a state of emergency with Tropical Storm Colin churning toward the state today, threatening serious flooding.

A large portion of Florida's western and Panhandle coast was already under a tropical storm warning when the National Hurricane Center announced that a swift-moving depression had become a named storm.

The center said it is the earliest that a third named storm has ever formed in the Atlantic basin.

Colin's maximum sustained winds Monday morning had increased to near 50 mph (85 kph) with some slow strengthening possible during the next two days.

The storm was centere dabout 285 miles (455 kilometers) west-southwest of Tampa and moving north-northeast near 16 mph (26 kph). AP