MIAMI -- Warm ocean waters could fuel an above-normal Atlantic hurricane season, while storm-suppressing El Nino conditions are expected to be scarce, U.S. government forecasters said Thursday.

The National Oceanic and Atmospheric Administration forecast calls for 11 to 17 named storms, with five to nine hurricanes. Two to four hurricanes are expected to be "major" with sustained winds of at least 111 mph.

Forecasters expect warmer-than-average waters across the tropical Atlantic Ocean and Caribbean Sea, weaker-than-average wind shear and a weak or nonexistent El Nino, said Ben Friedman, acting NOAA administrator.

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El Nino is the natural warming of parts of the Pacific Ocean that changes weather worldwide and tends to reduce hurricane activity in the Atlantic. Warm waters feed a hurricane's strength, while strong wind shear can starve it and pull a storm apart.

While climate models show considerable uncertainty, "there's a potential for a lot of Atlantic storm activity this year," Friedman said.

The long-term season averages are 12 named storms, with six hurricanes and three major ones. Tropical storms have sustained winds of at least 39 mph, and hurricanes have winds of at least 74 mph.

A new weather satellite will help forecasters see developing storms in greater detail, especially when it moves later this year into a permanent position over the East Coast with a view over the continental U.S. and tropical waters where hurricanes form, Freidman said.

"Its 'lightning mapper' allows us to see lightning in the clouds like we've never seen before," he said.

High-resolution hurricane model upgrades also are expected to provide "much improved" forecast guidance this year, said Mary Erickson, deputy director of the National Weather Service.

Officials urged coastal residents to make evacuation plans and stock up on emergency supplies long before any tropical weather advisory is posted.

The National Hurricane Center in Miami is adding advisories highlighting specific storm hazards: Storm surge watches and warnings will be issued when U.S. communities are at risk for life-threatening flooding. The "uncertainty cone" showing a storm's projected path will be updated to show how far damaging winds can reach. An experimental "time of arrival" graphic will show people when tropical storm-force winds are expected to start hitting their areas.

"Key data will be available earlier than ever to make informed decisions," said Robert Fenton, acting administrator of the Federal Emergency Management Agency.

The six-month Atlantic storm season officially starts June 1.

A rare April tropical storm formed this year over the open ocean: Arlene, which was no threat to land. The next tropical storm will be named Bret.

The 2016 hurricane season also started early with a January hurricane. It was the first above-normal season since 2012, with 15 named storms, seven hurricanes and four major hurricanes.

Five storms made landfall in the U.S. last year, including hurricanes Hermine and Matthew.