WASHINGTON — Relief might be on the way for a weather-weary United States with the predicted warming of the central Pacific Ocean brewing this year that will likely change weather worldwide. But it won't be for the better everywhere.

The warming, called an El Niño, is expected to lead to fewer Atlantic hurricanes and more rain next winter for drought-stricken California and Southern states, and even a milder winter for the nation's frigid northern tier next year, meteorologists say.

Although it could be good news to lessen the southwestern U.S. drought and shrink heating bills next winter in the far north, "worldwide it can be quite a different story," said North Carolina State University atmospheric sciences professor Ken Kunkel. "Some areas benefit. Some don't."

Globally, it can mean an even hotter year coming up and billions of dollars in losses for food crops.

The National Oceanic and Atmospheric Administration on Thursday issued an official El Niño watch.

Mike Halpert, acting director of NOAA's Climate Prediction Center, said the El Niño warming should develop by this summer, but there are no guarantees. Although early signs are appearing a few hundred feet below the ocean surface, meteorologists say an El Niño started to brew in 2012 and then shut down suddenly and unexpectedly.

Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research, who wasn't part of NOAA's forecast, agreed that an El Niño is brewing.

"This could be a substantial event, and I think we're due," Trenberth said. "And I think it could have major consequences."

Halpert said it is too early to say how strong this El Niño will be. The last four have been weak or moderate, and those have fewer effects on weather.

Scientific studies have tied El Niños to farming and fishing problems and to upticks in insect-born disease, such as malaria. Commodity traders even track El Niño cycles. A study by Texas A&M University economics professor Bruce McCarl found the last big El Niño of 1997-98 cost about $3 billion in agricultural damage.

Trenberth said this El Niño might even push the globe out of a decade-long slowdown in temperature increase, "so suddenly global warming kicks into a whole new level."

Explaining El Niño

An El Niño is a warming of the central Pacific once every few years, from a combination of wind and waves in the tropics. It shakes up climate around the world, changing rain and temperature patterns. The flip side of El Niño is La Niña, which has a general cooling effect. It has been much more frequent than El Niños lately, with five La Niñas and two small-to-moderate El Niños in the past nine years. The last big El Niño was 1997-98.