In its April forecast, the noted CSU team founded by forecasting pioneer Bill Gray, said the season would see 12 storms, including six hurricanes.

Two of the five hurricanes are expected to develop into "major" storms of Category 3 or higher on the Saffir-Simpson scale of hurricane intensity.

Gray's team said sea surface temperatures in the tropical Atlantic are cooler than normal. Hurricanes draw energy from warm water, so cooler water temperatures can lead to fewer and less intense hurricanes.

The researchers also cited the possible development of an El Nino, the warm-water phenomenon in the eastern Pacific Ocean that can suppress hurricane activity in the Atlantic.

"We believe that there is a slightly greater chance of a weak El Nino developing this summer/fall than there was in early April," Gray said in a statement. "El Nino conditions would likely increase levels of vertical wind shear and decrease Atlantic hurricane activity."

Many hurricane forecasters have called for a quieter season than last year, which saw 16 tropical storms, including eight hurricanes.

It was a rough year for Haiti, where more than 800 people were killed in four tropical storms and hurricanes, and Cuba, which was hit by three major hurricanes and sustained at least $10 billion in damage.