(CNN) -- The National Oceanic and Atmospheric Administration revised its predictions Thursday, saying more named storms are likely in this year's Atlantic hurricane season.
The agency now predicts between 12 and 17 named storms from the period that started on June 1 and will end on November 30. NOAA's original May prediction was between nine and 15 named storms.
The chance of an above-normal hurricane season rose to 35%, said Gerry Bell, the lead hurricane season forecaster at NOAA's Climate Prediction Center. There is a 50% chance of a "near-normal" season.
NOAA predicts that five to eight of the named storms will become hurricanes, and that two to three of those could be major hurricanes. A hurricane that reaches Category 3 or greater (with winds of at least 111 mph) is considered major.
A "normal" hurricane season produces 12 named storms, including six hurricanes, of which three are major hurricanes.
"We are increasing the likelihood of an above-normal season because storm-conducive wind patterns and warmer-than-normal sea surface temperatures are now in place in the Atlantic," Bell said. "These conditions are linked to the ongoing high activity era for Atlantic hurricanes that began in 1995. Also, strong early-season activity is generally indicative of a more active season."
This season has already produced six names storms: Alberto, Beryl, Chris, Debbie, Ernesto and Florence. Chris and Ernesto became hurricanes.
This year was also the first time since 1908 that three named storms formed before the June 1 start of hurricane season.
However, Bell said that other factors oppose some of the indications of an above-average storm season.
One of these is the weather phenomenon known as El Niño, which he said will probably develop later in the season.
"El Niño is a competing factor, because it strengthens the vertical wind shear over the Atlantic, which suppresses storm development," he said.
Laura Furgione, acting director of NOAA's National Weather Service, stressed in a conference call with reporters the importance of being prepared for a hurricane.
Apathy about preparedness is a challenge that the public faces, she said.
"People should be ready now," she said.
The warning is not just for coastal residents, Furgione added, as flooding from hurricanes can affect residents far inland.
CNN's Dave Hennen contributed to this report.