More tropical cyclones could stir off South Carolina's coast in the spring and early summer if the warmer-than-usual ocean waters follow their expected course, forecasters say.

The waters offshore, and in the Gulf of Mexico, could spur stronger storms during the heart of the summer hurricane season as well.

That's the unsettling reality for coastal residents and the entire state a year after Hurricane Matthew killed at least five people in South Carolina and caused more than $100 million in damage here.

Meanwhile, the Grand Strand and the Lowcountry stand about an even chance of being wracked by one, partially because the waters off South Carolina, as well as in the Gulf of Mexico, never cooled to their expected winter temperatures.

"That heat has to go somewhere," said Len Pietrafesa, research scholar at Coastal Carolina University and a former federal climate and severe storm researcher. "We have seen that, under the right atmospheric conditions, those warm water masses actively have popped up early season storms."

Pietrafesa is part of a university-based team that produces seasonal storm numbers and landfall probability predictions. They expect to have a 2017 forecast by mid-April, he said. The season officially runs from June through November. 

Meteorologist Bob Henson, of Weather Underground, said the Gulf's warm waters could keep pushing pulses of stormy weather into the Southeast. Those storm waves already have spurred relatively early outbreaks of tornadoes across the region. 

Because of the warm seas, the Southeast could see more hurricanes during the heart of the hurricane season, usually from August through October. But that's not a given, forecasters say. What's more likely is the waters would make any storm stronger when it does emerge.

Recent research by the University of Miami and others suggest that tropical cyclones, such as Matthew, strengthen when they hit what the study termed "massive rings of warm water."

Storms out of the Gulf are a more frequent threat for South Carolina. Four times as many storms that damaged the state in the past 25 years — more than 30 — came overland from the Gulf or from Florida rather than from the Atlantic, according to a review of S.C. Climate Office records by The Post and Courier.

Coming through the Gulf and up the Southeast coast, Matthew killed hundreds and did billions of dollars in damage.

"Even if Matthew had not made landfall here it would have caused a lot of damage because it was so close to the coast," Pietrafesa said. "That's a worst-case scenario, particularly if a storm moves slowly, a storm where everybody gets whacked."

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Science and environment reporter. Author of Washing Our Hands in the Clouds.