Tropical Storm Ana — arriving early and promising a messy Mother’s Day weekend for the Carolinas — became the first named storm of a 2015 hurricane season that doesn’t officially start until June 1.
The storm, technically classified as a “subtropical” system on Friday, posed no threat to Florida but could bring heavy rain and surf to a swath of the southeastern coast.
“There’s just that little prefix ‘sub,’ which will have meaning to meteorologists. But to the public it shouldn’t matter,” said James Franklin, chief of the center’s hurricane specialist unit.
Hurricane forecasters issued tropical storm warnings for parts of South Carolina and a watch in North Carolina. Late Friday, Ana’s sustained winds were 45 mph but cooler waters in its path were expected to limits its intensity, Franklin said. Rip currents and rain, forecast at between four and six inches, pose the biggest danger. A one to two-foot storm surge could also roll ashore.
Until the 1990’s, Ana would have remained a nameless event as a subtropical storm, Franklin said. Unlike tropical storms fueled by seasonal warm water, subtropical systems pull energy from both warm water and warm and cold air colliding in the atmosphere. They are typically slower to change, pack more wind than rain and are more loosely organized than compact tropical storms. They can evolve as they begin drawing more energy from the ocean, as Ana was expected to do Friday night.
But to those in their path, the effects are the same, which led hurricane forecasters to begin naming them.
“We wanted the public to treat them in the same way,” Franklin said.
May storms, while relatively rare, occur every six years on average, Franklin said. The last named storm was Beryl in 2012. In 2003, another Ana arrived on April 20, a full month before the official season start on June 1. Since 1851, the Atlantic has produced 23 May storms, he said.