Warmer than normal temperatures and continued drought are likely this winter in the West, government forecasters said Thursday. But the annual winter outlook from the National Weather Service contains considerable uncertainty for much of the nation with forecasters finding few strong trends to guide them.
ACCORDING TO the forecast, temperatures in Alaska, the far West, Southwest and Southern Plains are likely to be above normal this winter.
But, the report said, for other parts of the nation, the winter will bring equal chances of above-, below- or near-normal temperatures.
“Without a strong El Nino or La Nina signal as a guide, there is more uncertainty in our forecast, but we do expect winter to bring its typical weather variability,” said John Jones, Jr., deputy director of the National Weather Service.
El Nino and La Nina are unusual conditions in the central and eastern Pacific Ocean that can affect weather around the world. In an El Nino year, Pacific water is unusually warm, while the opposite is true in La Nina.
Lead forecaster Ed O’Lenic said the reason that the ocean is so important is that, where it’s warm there tend to be clouds. “Clouds are like drumsticks beating on a drum, and the atmosphere is the drum. If you beat it in the right place, you can get disturbances over the United States,” he said. But “the ocean temperatures haven’t settled down and we don’t know where the clouds are going to be.”
This winter’s forecast does indicate that the multiyear drought in the West will probably continue, with lingering water shortages.
Jones said researchers are studying other climatic factors that influence longer-range outlooks, but these aren’t yet routinely predictable on seasonal time scales.
Among the factors considered, he said, tropical ocean temperatures in the western Pacific and Indian oceans, atmospheric circulation patterns in the Arctic and North Atlantic, snow cover in the high latitudes during the late fall and U.S. soil moisture conditions.
“While ocean temperatures in the tropical Pacific are warmer than long-term averages and may even reach the level of a weak El Nino by late November, El Nino is not expected to exert a major influence on U.S. climate this winter,” Jones said.
The result is a large amount of uncertainty in the outlook.
In Alaska, the far West, the Southwest, and the southern Plains, temperatures will are expected to be warmer than the long-term averages. Elsewhere, there are equal chances of above, below and normal temperatures.
The majority of the nation will have equal chances of above, below and normal precipitation, except for Texas, Oklahoma and areas of western Louisiana, southwestern Arkansas and eastern New Mexico, where above normal moisture is likely.
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