ISSUES FINAL FORECAST FOR 2006-2007 U.S. WINTER SEASON
Nov. 16, 2006 — Meteorologists at the NOAA Climate Prediction Center today released the latest U.S. seasonal outlook and reiterated once again this winter is likely to be warmer than the 30-year norm (1971-2000) over much of the nation, yet cooler than last year's very warm winter season. NOAA's heating degree day forecast for December, January and February projects a 2 percent warmer winter than the 30 year average but about 9 percent cooler than last year. (Click NOAA image for larger view of winter temperature outlook for December 2006 through February 2007. Click here for high resolution version. Please credit “NOAA.”)
Meanwhile, a strengthening El Niño event continues to develop in the equatorial Pacific and is likely to continue into spring 2007. "During moderate as well as strong El Niño episodes, an increase in the occurrence of extreme cold days, especially in the Northeast, becomes less likely," said Vernon Kousky, research meteorologist at the NOAA Climate Prediction Center. "However, this current event is not expected to reach the magnitude of the very strong 1997-1998 El Niño episode," he added.
U.S. Winter Outlook
The precipitation outlook calls for wetter-than-average conditions across the entire southern tier of the country from central and southern California across the Southwest to Texas and across the Gulf Coast to Florida and the south Atlantic Coast. Drier-than-average conditions are favored in the Ohio and Tennessee Valleys, the northern Rockies and Hawaii. Other regions, including Alaska, have equal chances of drier, wetter or near average precipitation. Averages vary from location to location and are based on the 1971-2000 base period.
The Winter Solstice or astronomical winter begins on December 22, when the noontime sun is farthest south in the sky in the Northern Hemisphere. However, meteorologists define winter by the onset of winter-like weather conditions, which occurs earlier as one moves northward. Meteorological winter, roughly speaking, begins on December 1 over much of the continental United States.
CLIMATE FACTORS HELPING TO SHAPE WINTER 2006-2007
As winter 2006-07 approaches, NOAA scientists say the leading climate patterns expected to impact this winter's weather are long-term climate trends and features such as the El Niño/Southern Oscillation (ENSO), which influence the jet stream and the track storms take across the eastern Pacific and North America. These patterns form the physical basis for the NOAA Climate Prediction Center 2006/2007 U.S. Winter Outlook.
Niño Southern Oscillation (ENSO)
The NAO can be a major source of intra-seasonal variability over the eastern half of the United States, North Atlantic and Europe during winter. It modulates the circulation pattern over the middle and high latitudes, thereby regulating the number and intensity of significant weather events affecting the U.S.
phase features a strong polar vortex, with the mid-latitude jet stream
shifted to the north of its normal position. Associated with this phase
is an increase in the occurrence of extreme warm days over much of the
contiguous United States.
Implications for the U.S. in Winter 2006-2007
of these climate factors will be included—when applicable—in
Hazards Assessment, which is published online every Tuesday at the
NOAA Climate Prediction Center, while the status of ENSO is described
in the Weekly
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