“If you look in the Gulf of Mexico, when the ocean is warm, the main impact…will be to increase the frequency of weaker hurricanes and tropical storms,” Mr. Dailey said.

“The impact along the Southeast Coast, which would extend from the southern tip of Florida to Cape Hatteras, N.C., is an increase in stronger hurricanes,” he added.

Speaking to how much change in activity the data showed, Mr. Dailey said “we're talking about on the order of 10-to-15 percent increased frequency of weaker hurricanes along the Gulf Coast, and on the order of about 15-to-25 percent increased frequency of hurricanes, including some stronger ones, along the Southeast Coast. And that's an increase over the long-term average.”

Mr. Dailey said the reason why the Gulf Coast is at risk for an increase in tropical storms and smaller hurricanes as opposed to larger hurricanes with winds above 111 mph is because most storms that form in or near the Gulf of Mexico do not have a significant amount of warm ocean to travel over before they reach land.

“And that means they tend to not intensify to very strong storms before making landfall,” Mr. Dailey explained.

Conversely, he said, “in the Southeast, the storms that make landfall tend to originate over the center of the tropical Atlantic, and this region is called the Main Development Region (MDR). And storms that form over the MDR have a large, expansive ocean to intensify over before they reach land.” As a result, Mr. Dailey said, these storms have a greater probability of reaching hurricane strength.

He noted that this research does not suggest a major storm could not and will not hit the Gulf Coast in a warm water year. Rather, he explained, it is meant to look at “how the long-term risk is altered under the current climate conditions.”

For the coastline from Cape Hatteras to the tip of Maine, Mr. Dailey said, there is not enough available data to make an assessment as far as the types of storms for which that area may be more at risk.

This is partly due to the historical lack of hurricanes making landfall in that area. “There have really only been a handful of hurricanes that have made landfall along the Northeast Coast even in the last hundred years,” Mr. Dailey said.

The research conducted by AIR Worldwide involved looking at the historical record for hurricane activity in the Atlantic basin, and then focusing only on the years that experienced warm water conditions.

These years accounted for roughly half of the years contained in the historical record, which dates back to around 1900. “Because we're only working with half of the data when we measure the warm climatology, the uncertainties associated with the results of that analysis will be higher than the uncertainties associated with a long-term analysis based on all of the data because the sample size is smaller,” Mr. Dailey noted.

He also stressed that the probabilities reported in the research are not intended to be a forecast for any given year. “You can't assume that you're going to realize these probabilities in any given year,” he said.

Mr. Dailey said AIR is providing two catalogs of simulated events for its U.S. hurricane model.

The first catalog is the “standard catalog,” in which the simulated events are based on all historical data. The second catalog is called the warm SST (sea surface temperature) condition catalog, which factors in the research regarding warm water conditions.

“So what an insurance company would see under this warm ocean condition is this elevated risk of weaker hurricanes in the gulf and an elevated risk of all hurricanes, especially stronger ones, in the Southeast U.S.,” Mr. Dailey said.