CSU Forecasters See Signs of Below-Average Hurricane Season

Hurricane Katrina, 2005. Photo by National Oceanic and Atmospheric Adminisration

Meteorologists at Colorado State University think an unusual El Niño event later this year could keep the 2017 Atlantic Basin hurricane season a little quieter than usual.

CSU’s preseason forecast for the coming summer suggests that 11 named tropical storms will form in the Caribbean Sea, Gulf of Mexico and Atlantic Ocean between June 1 and November 30. A tropical storm gets a name when its winds reach 39 mph.

The CSU meteorologists think four of those storms will become hurricanes with winds of at least 74 mph. And of those storms, two could become major hurricanes with winds exceeding 110 mph.

An El Niño occurs when waters in the Pacific Ocean off Peru and Ecuador are warmer than usual. The occurrence of the event is irregular, and sometimes several years pass between occurrences. The event can have widespread effects, including causing sea levels to rise or fall. That can kill seabirds, sea lions and coral and cause fish to migrate to cooler waters.

But an El Niño also causes stronger upper-level winds over the Atlantic that can make it difficult for hurricanes to form, and that can cause a quieter than usual hurricane season.

El Niños have been forming at least since the end of the last Ice Age about 10,000 years ago. But scientists have only been able to effectively monitor the events since the advent of weather satellites in the 1970s. Since then, only three strong El Niños have occurred—one in 1982-83 and another in 1997-98.

The last El Niño—one of the strongest on record—formed in 2015. CSU meteorologist Phil Klotzbach said it’s unusual to have another El Niño so soon after the most recent one, “especially since the last El Niño we had was quite strong.”

“We’ve had two years between El Niño events in the past, but typically, both of them are quite weak,” Klotzbach said.

Another oddity of the current developing El Niño is that it’s developing in an eastward direction. The event usually develops in a westward direction, Klotzbach said.

CSU meteorologists also noted in their forecast that Atlantic water temperatures are cooler than usual. Hurricanes draw their energy from warm ocean waters, and cooler waters could mean fewer hurricanes are likely to form, the CSU scientists said.

The CSU meteorologists will update their forecast on June 1, July 3 and August 2.

“The CSU forecast is intended to provide a best estimate of activity to be experienced during the upcoming season – not an exact measure,” the forecasting team said in a prepared statement.

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Willie Drye is an award-winning author and a contributing editor for National Geographic News. He and his wife live in Wilmington, North Carolina.