The two Colorado State University climatologists now call for eight hurricanes, including three major ones to emerge this season. In June, they forecast nine hurricanes, four of them major, with sustained winds greater than 110 mph.
They also put the probability of at least one major hurricane striking the U.S. coastline at 64 percent, down from 72 percent in their earlier outlook.
They put the odds of a major system hitting the U.S. East Coast, including the Florida peninsula, at 40 percent, down from an earlier 48 percent.
They continue to predict a total of 18 named storms will develop over the entire season. That would amount to 14 more over the remainder of the season, as four already have formed.
Because waters in the eastern Atlantic near Africa have cooled somewhat, Klotzbach and Gray say some systems could be hampered.
Still, if their predictions hold, it would be a busier than normal year. On average, 12 named storms, including six hurricanes, three major, develop per season.
Put another way, this year's activity should be about 150 percent of the average season. By comparison, 2012 saw 131 percent of the average season - with 19 named storms, including 10 hurricanes.
They expect above normal activity mainly because El Nino, the atmospheric pattern that inhibits storm formation, is unlikely to develop this year.
"Typically, El Nino is associated with stronger vertical shear across the tropical Atlantic, creating conditions less conducive for storm formation," Klotzbach said.
Also, the Atlantic remains in an era of heightened tropical intensity, the result of a natural cycle, he added.
At least for the next two weeks, tropical activity near Africa should be slow because of a Saharan dust storm, Klotzbach said.
"The strong Saharan dust layer should really kill anything coming off of Africa for awhile," he said.
The National Oceanic and Atmospheric Administration will update its outlook on Aug. 8. The agency in May called for up to 20 named storms, including up to 11 hurricanes, or what could amount to an extremely active season.
"All vulnerable coastal residents should make the same hurricane preparations every year, regardless of how active or inactive the seasonal forecast is," Gray said.
©2013 Sun Sentinel (Fort Lauderdale, Fla.)
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