Plan on another turbulent storm season – the fourth in a row, Phil Klotzbach and William Gray said Wednesday.

Their 2013 Atlantic hurricane season forecast: 18 named storms, including nine hurricanes, four major. The average season sees 12 storms, including six hurricanes, three with winds greater than 110 mph.

The two Colorado State University climatologists say the tropical Atlantic is unusually warm and El Niño, the atmospheric force that inhibits storm formation, is unlikely to emerge this season, which starts June 1 and runs through Nov. 30.

“Typically, El Nino is associated with stronger vertical shear across the tropical Atlantic, creating conditions less conducive for storm formation,” Klotzbach said.

Another factor: The Atlantic basin remains in an era of tropical intensity, where more hurricanes tend to form, the result of a natural cycle, they say.

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