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
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