MIAMI — Federal forecasters expect a near-normal Atlantic hurricane season, after three relatively slow years. But they also say climate conditions that influence storm development are making it difficult to predict how many hurricanes and tropical storms will arise over the next six months.

The National Oceanic and Atmospheric Administration's outlook Friday called for a near-normal season with 10 to 16 named storms, with four to eight hurricanes and one to four “major” ones with winds reaching 111 mph and up.

The long-term season averages are 12 named storms, with six hurricanes and three major ones.

The Atlantic hurricane season officially starts June 1, but tropical weather got a head-start this year: Hurricane Alex made an unseasonable debut in January over the far eastern Atlantic.

The National Hurricane Center says an area of low pressure between Bermuda and the Bahamas had a high chance of brewing into something bigger Friday or Saturday.

Hurricane hunter aircraft investigated the disturbance Friday, and communities along the coasts of Georgia and the Carolinas should monitor its development, said NOAA Administrator Kathryn Sullivan.

While they can't predict whether any storm will strike the U.S., and more tropical storms are expected than in the last three years, NOAA officials said significant variables are at play.

It's unclear whether a decadeslong high-activity era for Atlantic hurricanes has ended, said Gerry Bell, lead seasonal hurricane forecaster with the NOAA's Climate Prediction Center.

Meanwhile, El Nino is dissipating while La Nina looms for the season's peak from August through October.

El Nino is the natural warming of parts of the Pacific Ocean that changes weather worldwide. That tends to reduce hurricane activity in the Atlantic, while La Nina tends to increase it.

The active storm era associated with warm Atlantic temperatures and stronger West African monsoons began in 1995, but recent hurricane seasons showed shifts toward a cooler phase marked by colder waters and a weaker monsoon, Bell said.

Each era can last 25 to 40 years, and it might take years to determine whether the transition has happened, Bell said.

The last transition to a less active hurricane era happened in the 1970s, without the data and computer models that forecasters have now.

“We're watching it for the first time with very new eyes,” Sullivan said.

The 2015 season was below average with 11 named storms, including two tropical storms that made landfall and caused flooding in South Carolina and Texas. Hurricane Joaquin, one of two storms to reach major hurricane strength, killed all 33 mariners aboard a cargo ship that sank off the Bahamas in October.

During U.S. Coast Guard investigative hearings this month into the sinking of the El Faro, one federal investigator characterized the disaster as “a colossal failure” of management.

Initial forecasts for Joaquin also were wildly inaccurate. Sullivan said the NOAA is on track to meet storm track and intensity forecast improvement goals, and a new weather satellite launching this fall will produce much sharper images of hurricanes and other severe weather.

The last major hurricane to strike the U.S. mainland was Hurricane Wilma, which cut across Florida in 2005. Wind speeds, not damage estimates, determine whether a hurricane is classified as “major” — that's Category 3 and up on the hurricane wind scale.

Since 2005, the population in the 185 coastline counties most threatened by hurricanes has grown 8.7 percent to 59.2 million people, according to U.S. Census estimates. Overall, 143.6 million — 44.7 percent of the U.S. population — from Maine to Texas could be living in harm's way.