DENVER, Colorado (AP) – Cooler water in the Pacific and more atmospheric dust from Africa prompted hurricane researcher William Gray to lower his 2007 forecast slightly yesterday, calling for 15 named storms and eight hurricanes off the East and Gulf coasts of the US

Gray’s forecast calls for four of the hurricanes to be intense.

On May 31, at the outset of the hurricane season, he had called for 17 named storms and nine hurricanes, five of them intense.

Despite the reduction, Gray said, the indicators tracked by his team at Colorado State University call for 60 per cent more storm activity than the long-term average.

The June 1-November 30 Atlantic hurricane season averages 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.

“Nobody knows for sure, but if the future is like the past, there are these precursor signals out there in the atmosphere on a global scale that indicate an active season,” he said.

Surface temperatures in the Pacific, and Sahara Desert dust blocking solar energy from warming the Atlantic, are part of a complex web of factors in hurricane formation, Gray said.

Others include atmospheric pressure and Atlantic water temperatures that are affected by circulation patterns, he said.

A study issued this week said the number of tropical storms developing in the Atlantic each year has more than doubled over the past century and coincided with rising sea-surface temperatures.

The study, published online by Philosophical Transactions of the Royal Society of London, said the increase in sea temperature was largely the byproduct of human-induced climate warming.

Gray, whose views on global warming are controversial among some climate scientists, disputed that conclusion.

Gray said changes in the number and intensity of hurricanes are cyclical and not caused by human influence.

“We don’t attribute this to human-induced global warming,” he said. “These are just natural changes.”

His new forecast calls for three named storms, two hurricanes and one intense hurricane in August; five named storms, four hurricanes and two intense hurricanes in September; and five named storms, two hurricanes and one intense hurricane in October and November combined.

There were 10 named Atlantic storms last year and five hurricanes, two of them major. None of the hurricanes hit the US coast.

The latest forecast put the chances of an intense hurricane hitting the US coastline at 68 per cent for the rest of this season. Chances of an intense hurricane hitting the East Coast, is 43 per cent.

The forecast also called for above-average risk of a major hurricane making landfall in the Caribbean.

The devastating 2005 season set a record with 28 named storms, 15 of them hurricanes. Four hurricanes hit the US, including Katrina, which devastated parts of the Gulf Coast.