Rising heat in the equatorial Pacific Ocean portends the quietest Atlantic hurricane season in five years, Colorado State University researchers said.

Nine named storms, with winds of at least 39 miles (63 kilometers) per hour, are expected to develop this year, with three of them growing into hurricanes and one becoming a major storm, said Phil Klotzbach, lead author of the forecast.

“The low forecast is due to El Nino’s likely development” in the Pacific and “cool sea surface temperatures in the tropical Atlantic,” Klotzbach said in an e-mail interview.

The Atlantic hurricane season is watched closely by the energy, commodity and insurance industries because of the effect hurricanes have on lives, property and markets in the U.S., Mexico and the Caribbean.

The Gulf of Mexico is home to about 6 percent of U.S. natural gas output, 23 percent of oil production and more than 45 percent of petroleum refining capacity, according to the Energy Department.

In 2001, Gulf waters accounted for 24 percent of U.S. marketed gas production. Florida, which has been struck by more tropical systems than any other state, is the second-largest producer of oranges behind Brazil.

Quiet Seasons

The last time the Atlantic produced only nine named storms was 2009, which was also a year in which an El Nino formed, according to the National Hurricane Center in Miami. That was the least number of such storms since 1997, which had eight.

El Nino is important to the forecast because warm waters in the equatorial Pacific trigger atmospheric changes that lead to more wind shear across the tropical Atlantic.

Shear is when winds at different altitudes blow in multiple directions or speeds. That can tear apart the structure of a budding tropical system, rip the top off a hurricane or knock a storm over, weakening it or breaking it apart.

The U.S. Climate Prediction Center has issued an El Nino watch this year, and the Australian Bureau of Meteorology says the chances are greater than 70 percent that one will form.

Colorado State’s hurricane outlook is one of the leading forecasts because William Gray, now professor emeritus of atmospheric science, pioneered seasonal predictions.

Last year, the researchers expected 18 storms, eight of them hurricanes and three of them major systems with winds of at least 111 mph. There were 14, two of which became hurricanes. None was major. One of the storms was added to the seasonal total in February after the hurricane center reanalyzed data.

The 30-year average is 12 named storms, six hurricanes and three major systems, according to the center. The six-month Atlantic season begins June 1.

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