COLORADO (Bloomberg) — Colorado State University has cut its forecast for the 2009 Atlantic season to five hurricanes, from a prediction of six in April.

Researchers William Gray and Phil Klotzbach said the 2009 Atlantic season will be "slightly below-average". It will produce two major hurricanes, with winds of at least 111 miles (178 kilometres) per hour, and 11 named storms, according to a statement. In April they forecast two major hurricanes and 12 named storms in the season, which runs from June 1 to November 30.

The researchers lowered their forecast because they expect cooler-than-normal water temperatures in the tropical Atlantic and a rising potential for a so-called El Nino event in the Pacific.

"El Nino conditions would likely increase levels of vertical wind shear and decrease Atlantic hurricane activity," said Gray, who is entering his 26th year forecasting hurricanes at the university.

The Fort Collins, Colorado-based school's forecasts are followed by insurers and energy markets. Yesterday's forecast is the second revision to a preliminary estimated issued in December.

In April 2008, Gray and Klotzbach predicted 15 named storms would form. They maintained that forecast in June, and then in August they raised the outlook to 17. The 2008 season spawned an above-average 16 named storms.

The Atlantic storms can threaten the Gulf of Mexico, which accounts for about 26 percent of US oil production and 14 percent of its gas.

This is the second time the pair have reduced their forecast for the 2009 Atlantic season.

In December, the school issued a preliminary estimate of 14 named storms for 2009.

Forecasters including the US National Oceanic and Atmospheric Administration have called for fewer tropical storms than last year because of the cooler Atlantic and warming currents in the eastern Pacific.

NOAA last month forecast nine to 14 named storms to form in the Atlantic during the season. Four to seven of the storms will become hurricanes, two of them major, NOAA said.