The outlook is “murky” for the El Nino weather pattern to persist during the heart of the Atlantic hurricane season, potentially clearing the way for more storms, the U.S. Climate Prediction Center said.

The center dropped the odds that El Nino will last through the three months ending Oct. 31 to 55 percent from 60 percent in May amid mixed signals from oceans and the atmosphere. Without El Nino to act as a brake, the Atlantic hurricane season may heat up during the peak in September.

“The analogy would be forecasting now is like trying to find a polar bear in a blinding snow storm,’’ Michelle L’Heureux, a forecaster at the center in College Park, Maryland. “One thing that we start looking for in June and July is tendencies in the tropical Pacific that seem to be moving in a certain direction, and now they are all moving in opposite directions.’’

Warm water in the Pacific Ocean’s depths is being offset by an increase in trade winds, often associated with a cooler surface.

“They are really diametrically opposite right now,’’ L’Heureux said. “We have to see which one wins. Right now, it is hard to tell because they are about equal to each other.’’

El Ninos occur as a warming equatorial Pacific spurs a reaction from the atmosphere, upsetting weather patterns across the globe. In the Northern Hemisphere’s summer, El Nino promotes wind shear across the Atlantic that can tear apart budding tropical storms and hurricanes.

Most seasonal outlooks for the Atlantic take El Nino into consideration for forecasts the potential number of storms in the six-month season.

Atlantic hurricanes can roil commodity, energy and financial markets. Along the U.S. Gulf and Atlantic coasts, $1.8 trillion of real estate and 7.3 million homes are at risk, according to CoreLogic, a consulting firm based in Irvine, California.

In addition, the Gulf Coast accounts for 45% of U.S. refining capacity, while 17% of the nation’s crude comes from the Gulf of Mexico. Florida is the world’s second-largest citrus producer.

El Ninos raise the chances Brazil can be warmer than normal and leave India, Indonesia and eastern Australia drier. The influence on the U.S. summer tends to be weak, though cooler- than-normal temperatures may crimp natural gas demand.

“Certainly in June, it appears that signal is winning out,’’ L’Heureux said.

The central U.S. has a good chance of being cooler than average across the northern Great Plains and Midwest from June 17 to 25, the center said.

On Tuesday, the Australian Bureau of Meteorology said the Pacific will likely shift away from El Nino thresholds in coming months. The country uses different criteria to define the event and hasn’t declared the pattern underway.

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