The revised forecast by William Gray and his team at Colorado State University includes one more named storm than the previous forecast.
The long-term average is about 10 named storms, including six hurricanes. Of those, two are "intense" hurricanes, defined as those with sustained wind of at least 111 mph.
The Colorado State team also warned the chances of at least one intense hurricane making landfall in the United States is 71 percent, much higher than the long-term average of 52 percent.
For the East Coast, the probability of an intense hurricane making landfall is 52 percent, compared with a long-term average of 31 percent.
For the Gulf Coast from the Florida Panhandle to Brownsville, Texas, the probability is 40 percent, compared with a long-term average of 30 percent, Gray's team said.
Higher hurricane numbers over the past seven to nine years indicate the United States has entered a period of increased storms that will last two or three decades, said Philip Klotzbach, an atmospheric research scientist and a member of the forecast team.
The change correlates to an increase in surface temperatures in the North Atlantic and a decline in surface pressure in the tropical Atlantic.
The team said it didn't attribute the changes to human-caused global warming.
Storms are given names when sustained wind reaches 39 mph. They become hurricanes if the speed increases to 74 mph.
The Atlantic hurricane names for 2004 are: Alex, Bonnie, Charley, Danielle, Earl, Frances, Gaston, Hermine, Ivan, Jeanne, Karl, Lisa, Matthew, Nicole, Otto, Paula, Richard, Shary, Tomas, Virginie and Walter.