El Nino weather patterns fully developed

From Brad Wright
CNN

Warm water in the South Pacific is indicated in yellow and orange in this infrared satellite image taken December 9.

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WASHINGTON (CNN) -- The government's top weather forecasters said Thursday the nation's weather is being affected by a classic "el Nino" weather pattern that is bringing needed rain to the South and will result in slightly warmer temperatures in the North.

"We've already seen the effects," of the el Nino pattern, said Jack Kelly, director of the National Weather Service. "The northern half of the country is going to be warmer than normal and the southern half of the country is going to have more storms than normal. We've already seen that -- we're in December and we've had two winter storms."

People in the northern states may not even notice the temperature difference. "Chicago will still be cold, just not as cold," said James D. Laver, director of the Climate Prediction Center.

Kelly said drought conditions in the southern states have been eased a bit amid recent stormy weather.

"That increased storminess helped relieve the drought that they had been experiencing for some years," said Kelly. "So, in truth, where a lot in this country tend to view (El Nino) as having a negative impact on our weather, from an economic point of view it actually has a positive impact."

The Commerce Department says that about one-quarter of the U.S. economy -- some $2.7 trillion -- is affected by the weather.

The National Oceanographic and Atmospheric Administration uses temperatures over the past 30 years to establish a baseline for normal temperatures.

El Nino is the name of the cyclical event in which waters in the tropical Pacific Ocean become warmer, triggering a chain reaction that results in weather anomalies across the globe.

Kelly said the most noticeable effect of El Nino may have been on hurricanes. "Hurricanes are cyclical in nature and we're in the phase where they are more active," Kelly said. "We had less than half than the normal number of hurricanes that one might anticipate if you were in this phase were it not for (El Nino)."

In three to six months, the Pacific Ocean temperatures are expected to recede in what's called a neutral phase, then cool further to produce a "la Nina" pattern that will probably cause more moderate weather effects, forecasters say.

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