NOAA ISSUES FINAL FORECAST FOR 2006-2007 U.S. WINTER SEASON
December, January, February Forecast Still On Track

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.

The U.S. Winter Outlook
Overall, NOAA seasonal forecasters expect warmer than average temperatures across the Pacific Northwest, the northern and central plains, the Midwest, the Northeast and northern mid-Atlantic, as well as most of Alaska during December 2006 through February 2007. Near-average temperatures are favored for parts of the Southeast from Louisiana through North Carolina, while below-average temperatures are anticipated for Hawaii. Parts of the mid-Atlantic, the Tennessee Valley, the Southwest from Texas to California and the intermountain West have equal chances of warmer, cooler and near-normal temperatures this winter. (Click NOAA image for larger view of winter precipitation outlook for December 2006 through February 2007. Click here for high resolution version. Please credit “NOAA.”)

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.

Winter Weather Safety
"The prediction for a warmer than normal winter season does not mean we won't have winter weather," said Mike Halpert, lead seasonal forecaster at the NOAA Climate Prediction Center. "What it does mean is that on average this will be a milder than average winter across much of the North, with fewer arctic air outbreaks," he added. The NOAA National Weather Service has a plethora of weather safety news and information online, including NOAAWatch, a portal to a variety of current weather information, and NOAA Weather Radio All Hazards, a nationwide network of radio stations broadcasting continuous weather information directly from a nearby NOAA National Weather Service forecast office. NOAA Weather Radio broadcasts NOAA National Weather Service warnings, watches, forecasts and other hazard information 24 hours a day, 7 days a week.

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.

El Niño Southern Oscillation (ENSO)
El Niño conditions have developed across the Tropical Pacific during the past few months and are predicted to be the dominant factor affecting this winter’s climate. Water temperatures in the central-equatorial Pacific Ocean are more than 1.0 degree C (1.8 degrees F) above normal across this region and these departures are expected to persist or increase during the next few months. As a result, it's likely that the ENSO phenomena will be a significant factor influencing this winter season. El Niño events influence the position and strength of the jet stream over the Pacific Ocean, which affects the winter patterns of precipitation and temperature across the country.

Long-Term Climate Trends
Estimates of decadal trends often provide the foundational basis for the seasonal forecast. One tool that is used at the NOAA Climate Prediction Center is the average conditions during the last 10 years compared to the long-term average for 1971-2000. The most recent 10-year trend during winter favors above normal temperatures across most of the country.

Forecast Uncertainty
The unpredictability of the seasonal phase of the North Atlantic Oscillation, or NAO, introduces some uncertainty in the winter outlook, especially for the Northeast. Currently, reliable forecasts of the NAO are on the timescale of weeks and not months in advance. However, NOAA research finds during moderate and strong ENSO episodes the presence of the negative phase of the NAO (an increase in the occurrence of extreme cold days) becomes less likely.

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.

The positive 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.

The negative phase features high-latitude blocking, frequently in the vicinity of Greenland. Associated with this phase, there is an increase in the occurrence of extreme cold days, especially from the Great Plains to the Southeast.

Implications for the U.S. in Winter 2006-2007

• The ENSO phenomena is likely to be the dominant factor influencing the winter weather in the United States;
• The unpredictability of the seasonal phase of the NAO always introduces uncertainty in the seasonal outlook, especially for the Northeast;
• During moderate and especially strong ENSO episodes, the negative phase of the NAO becomes less likely;
• Since moderate strength ENSO conditions are expected this winter, the Madden-Julian Oscillation is not anticipated to play a major role this winter.

The forecast of these climate factors will be included—when applicable—in the U.S. Hazards Assessment, which is published online every Tuesday at the NOAA Climate Prediction Center, while the status of ENSO is described in the Weekly ENSO Update.

The NOAA Climate Prediction Center is one of nine NOAA National Centers for Environmental Prediction located in Camp Springs, Md. The NOAA Climate Prediction Center monitors and forecasts short-term climate fluctuations and provides guidance information on the long-term global effects climate patterns can have on the nation.

In 2007 NOAA, an agency of the U.S. Commerce Department, celebrates 200 years of science and service to the nation. Starting with the establishment of the U.S. Coast and Geodetic Survey in 1807 by Thomas Jefferson much of America's scientific heritage is rooted in NOAA. The agency is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and information service delivery for transportation, and by providing environmental stewardship of the nation's coastal and marine resources. Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, more than 60 countries and the European Commission to develop a global monitoring network that is as integrated as the planet it observes, predicts and protects.

Relevant Web Sites
NOAA Climate Prediction Center Seasonal Outlooks

NOAA Climate Prediction Center

U.S. Seasonal Outlooks Predict Potential Future U.S. Climate & Weather

NOAA Forecast Products

NOAA Winter Weather Preparedness

NOAA El Niño/Southern Oscillation (ENSO) Diagnostic Discussion

NOAA Drought Information Center

Media Contact:
Carmeyia Gillis, NOAA Climate Prediction Center, (301) 763-8000 ext. 7163