Hurricanes May Increase in Gulf as El Nino Shifts in Pacific
July 2 (Bloomberg) -- A shift of warming patterns in the Pacific Ocean may mean more seasons of increased hurricane activity in the Atlantic and more storms entering the oil-rich Gulf of Mexico, according to a study in the journal Science.
The warming of Pacific waters -- a phenomenon called El Nino -- has been moving toward the central Pacific, meaning more storms will form in the Gulf and Caribbean, researchers at Georgia Institute of Technology said in the study. Traditionally, when the eastern Pacific warms up, hurricane activity in the Atlantic falls.
“What this is saying is, if El Nino is changing its character, which we think it is, you are going to get less of the down years in the Atlantic Ocean,” said co-author Peter Webster, a professor at the Atlanta university’s School of Earth and Atmospheric Sciences.
The study shows central Pacific warming is happening at the expense of regular El Ninos, and the years that it occurs are as active as when the eastern Pacific is cool. In addition, when the events occur, storms tend to follow paths to the Caribbean, the Gulf and the U.S. East Coast.
The idea that increased activity in the Atlantic can occur when the central Pacific warms up makes sense to Colorado State University hurricane researcher Phil Klotzbach because El Nino “is what really squashes the Atlantic hurricane season.”
Klotzbach and William Gray draw up closely followed seasonal hurricane forecasts at the university in Fort Collins.
Phenomenon Accelerates
Since 1960, and accelerating since 1990, there have been more instances of central Pacific warming development, taking away from traditional El Ninos, according to the study. The number of years when the eastern Pacific is cold, called La Nina, has remained the same.
The Gulf of Mexico is home to about 26 percent of U.S. oil production and 14 percent of gas. A shutdown of refineries in the region can cause spikes in gasoline prices and shortages, as happened last year after hurricanes Gustav and Ike.
El Nino brings low pressure over the eastern Pacific, which creates wind shear over the Atlantic that can keep storms from developing, said Josh Newhard, a meteorologist for AccuWeather.com in State College, Pennsylvania.
Webster, the study’s co-author, said when a warming system is moved about 2,485 miles (4,000 kilometers) west into the central Pacific, the entire dynamic changes.
‘Not Magic’
“It’s not magic; if you move that heating more to the central Pacific you are not increasing the shear as much over the Atlantic Ocean,” said Webster, who wrote the paper with the school’s Hye-Mi Kim and Judith Curry. “So what you finish up with is a possibility of more storms occurring in the western Atlantic ocean.”
Warming in the central Pacific can also be misidentified as an El Nino, leading to forecasts that underestimate the number and intensity of Atlantic storms, according to the study.
For example, Webster said, in 2002 the U.S. National Oceanic and Atmospheric Administration saw an increase in Pacific warming and predicted an El Nino that would bring below- normal activity and as many as 10 named storms to the Atlantic.
That season produced 12 named storms and NOAA’s end-of- season assessment attributed the extra activity to a decades- long increase in hurricane activity. Webster said his team believes the real reason for the added activity was central Pacific warming.
All the major seasonal hurricane forecasts this year, including those from Colorado State and NOAA, cited El Nino as part of their reasons for calling for fewer storms.
CSU Forecast
Last month, Colorado State predicted the current Atlantic season, which runs from June 1 to Nov. 30, would be “slightly below average” with 11 named storms, five of which would become hurricanes. NOAA forecast nine to 14 storms, fewer than last year’s above-average 16.
Currently, the U.S. Climate Prediction Center, a branch of the National Weather Service, has issued an El Nino watch. Webster said his team’s models suggest this El Nino will actually migrate and become another example of central Pacific warming.
If that holds up, the current hurricane season could see a greater number of late-season storms, he said.
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