High Resolution (Credit: NOAA)
Niño in the central and eastern equatorial Pacific Ocean is expected to
be a dominant climate factor that will influence the December through
February winter weather in the United States, according to the 2009
Winter Outlook released today by NOAA’s Climate Prediction Center. Such
seasonal outlooks are part of NOAA’s suite of climate services.
expect El Niño to strengthen and persist through the winter months,
providing clues as to what the weather will be like during the period,”
says Mike Halpert, deputy director of the Climate Prediction Center – a
division of the National Weather Service. “Warmer ocean water in the
equatorial Pacific shifts the patterns of tropical rainfall that in
turn change the strength and position of the jetstream and storms over
the Pacific Ocean and the U.S.”
“Other climate factors
are also likely to play a role in the winter weather at times across
the country,” added Halpert. “Some of these factors, such as the North
Atlantic Oscillation are difficult to predict more than one to two
weeks in advance. The NAO adds uncertainty to the forecast in the
Northeast and Mid-Atlantic portions of the country.”
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Highlights of the U.S. Winter Outlook (December through February) include:
High Resolution (Credit: NOAA)
are favored across much of the western and central U.S., especially in
the north-central states from Montana to Wisconsin. Though temperatures
may average warmer than usual, periodic outbreaks of cold air are still
- Below-average temperatures
are expected across the Southeast and mid-Atlantic from southern and
eastern Texas to southern Pennsylvania and south through Florida.
- Above-average precipitation
is expected in the southern border states, especially Texas and
Florida. Recent rainfall and the prospects of more should improve
current drought conditions in central and southern Texas. However,
tornado records suggest that there will also be an increased chance of
organized tornado activity for the Gulf Coast region this winter.
- Drier-than-average conditions are expected in the Pacific Northwest and the Ohio and Tennessee River Valleys.
Equal chances for above-, near-, or below-normal temperatures and
precipitation. Winter weather in this region is often driven not by El
Niño but by weather patterns over the northern Atlantic Ocean and
Arctic, such as the North Atlantic Oscillation. These patterns are
often more short-term, and are generally predictable only a week or so
- California: A slight tilt in the odds toward wetter-than-average conditions over the entire state.
Milder-than-average temperatures except along the western coast. Equal
chances for above-, near-, or below-median precipitation for most areas
except above median for the northwest.
- Hawaii: Below-average temperatures and precipitation are favored for the entire state..
seasonal outlook does not predict where and when snowstorms may hit or
total seasonal snowfall accumulations. Snow forecasts are dependent
upon winter storms, which are generally not predictable more than
several days in advance.
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