NOAA forecasters estimate 12 to 17 named storms of which five to nine of those will develop into hurricanes and one to four will become major hurricanes during the June 1 to Nov. 30 season.

A tropical storm brings sustained winds of at least 39 miles per hour (63 kph), a hurricane has winds of at least 74 mph and major hurricanes pack winds of at least 111 miles per hour and can bring devastating damage.

Last year broke a six-year string of above-normal hurricane seasons with the strongest that year being Hurricane Ian, which spawned 150 mph winds and hit Florida and South Carolina.

There is a 40% chance of a normal hurricane season and 30% chances each of an above-average or below-average season, NOAA Administrator Rick Spinrad said in a media briefing.

NOAA estimates a 93% chance of an El Nino weather phenomenon during the core hurricane season, said Matthew Rosencrans, NOAA's lead hurricane forecaster.

El Nino causes wind conditions in the upper atmosphere that slow down developing storms in the Atlantic Ocean. Its limiting influence on storms, however, could be offset by warmer ocean temperatures that create favorable conditions, NOAA said.

Atlantic Ocean surface temperatures "are warmer than we were last year and as warm was we were in 2020, Rosencrans told the media conference.

Normally when there is El Nino, the models call for between six and 18 named storms but the warm ocean temperatures have led to a combination not usually seen, Rosencrans added.

The combination has added significant uncertainty to this year's hurricane forecast, resulting in the certainty being a 40% chance of a normal hurricane season and not the normal 60%, he said.