Skip Navigation Links www.nws.noaa.gov 
NOAA logo - Click to go to the NOAA home page National Weather Service   NWS logo - Click to go to the NWS home page
Climate Prediction Center
 
 

CPC Search
About Us
   Our Mission
   Who We Are

Contact Us
   CPC Information
   CPC Web Team

Official 90-day Outlooks are issued once each month near mid-month at 8:30am Eastern Time. Please consult the schedule of 30 & 90-day outlooks for exact release dates.

Text Discussions
   90day Prognostic
   30day Prognostic
   Hawaiian
   Tools


More Outlooks
    0.5mn DJF 2017
    1.5mn JFM 2018
    2.5mn FMA 2018
    3.5mn MAM 2018
    4.5mn AMJ 2018
    5.5mn MJJ 2018
    6.5mn JJA 2018
    7.5mn JAS 2018
    8.5mn ASO 2018
    9.5mn SON 2018
   10.5mn OND 2018
   11.5mn NDJ 2018
   12.5mn DJF 2018
    0.5mn Dec 2017


Tools Used (see Discussion for explanation)
   CCA
   OCN
   CMP
   SMT
   POE
 
HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EST THU NOV 16 2017

30-DAY OUTLOOK DISCUSSION FOR DECEMBER 2017

THE DECEMBER 2017 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL
MODEL GUIDANCE, THE TYPICAL INFLUENCE ASSOCIATED WITH LA NINA, AND LONG-TERM
TRENDS. DURING THE PAST MONTH, LA NINA CONDITIONS DEVELOPED AS NEGATIVE SEA
SURFACE TEMPERATURE ANOMALIES CONTINUED ACROSS THE EASTERN AND CENTRAL
EQUATORIAL PACIFIC ALONG WITH SUPPRESSED (ENHANCED) CONVECTION ACROSS THE
CENTRAL TROPICAL PACIFIC (MARITIME CONTINENT AND PHILIPPINES). CLIMATE SIGNALS
TYPICALLY ASSOCIATED WITH LA NINA WERE CONSIDERED IN MAKING THE DECEMBER 2017
OUTLOOK, GIVEN THESE CURRENT ATMOSPHERIC AND OCEANIC STATES.

A ROBUST MJO OCCURRED DURING OCTOBER, BUT IT WEAKENED SINCE THE BEGINNING OF
NOVEMBER.  THE DYNAMICAL MODELS INDICATE A CONTINUED WEAK OR INCOHERENT SIGNAL
DURING THE NEXT TWO WEEKS. THEREFORE, THE MJO IS NOT EXPECTED TO PROVIDE ANY
FORCING TO THE EXTRATROPICS. ALTHOUGH THE MJO DID NOT FACTOR INTO THE DECEMBER
OUTLOOK, ITS EVOLUTION WILL BE CLOSELY MONITORED FOR THE REVISED OUTLOOK AT THE
END OF THE MONTH.

THE ARCTIC OSCILLATION (AO) INDEX IS FORECAST TO BECOME LARGELY NEGATIVE DURING
MID-NOVEMBER AS A BLOCKING RIDGE PERSISTS OVER THE BERING SEA WITH ANOTHER
UPPER-LEVEL RIDGE BUILDING OVER THE DAVIS STRAIT. THE DURATION OF THIS NEGATIVE
AO INDEX IS UNCERTAIN AND COULD BE TRANSIENT WITH MANY GFS ENSEMBLE MEMBERS
INDICATING THAT THE AO INDEX BECOMES MORE NEUTRAL BY THE END OF NOVEMBER. MOST
INPUTS TO THE NMME AGREE ON ENHANCED ODDS FOR ABOVE-NORMAL TEMPERATURES ACROSS
THE EASTERN CONUS. SINCE THE ECMWF MODEL AT WEEKS 3-4 (WHICH INCLUDES DEC
1-12)INDICATES INCREASED CHANCES FOR BELOW-NORMAL TEMPERATURES ACROSS MUCH OF
THE EASTERN CONUS AND GREAT LAKES, EQUAL CHANCES OF BELOW, NEAR, OR ABOVE
NORMAL TEMPERATURES ARE NECESSARY FOR THESE AREAS AT THIS TIME LEAD. THE
SPATIAL PATTERN OF THE TEMPERATURE FORECAST ACROSS THE WESTERN AND
SOUTH-CENTRAL CONUS IS SIMILAR TO THE SEASONAL OUTLOOK SINCE LA NINA WAS A
MAJOR FACTOR IN CREATING THE DECEMBER OUTLOOK, BUT THE COVERAGE OF AREAS WHERE
BELOW- AND ABOVE-NORMAL TEMPERATURES ARE FAVORED IS SMALLER DUE TO UNCERTAINTY.
DYNAMICAL MODELS, INCLUDING WEEKS 3-4, AND LONG-TERM TRENDS SUPPORT THE
RELATIVELY HIGH ODDS FOR ABOVE-NORMAL TEMPERATURES ACROSS THE SOUTHWESTERN
CONUS.

THE PRECIPITATION OUTLOOK FOR DECEMBER IS BASED PRIMARILY ON THE CALIBRATED
NMME AND IS CONSISTENT WITH LA NINA CONDITIONS AND THE DJF OUTLOOK. THE HIGHEST
PROBABILITIES FOR BELOW-NORMAL PRECIPITATION ARE FORECAST ACROSS PARTS OF THE
GULF COAST AND SOUTHEAST WHERE A DRY SIGNAL IS STRONG IN LA NINA COMPOSITES FOR
NDJ AND PROBABILITIES ARE RELATIVELY HIGH IN THE CALIBRATED NMME. THE BROAD
AREA OF ENHANCED ODDS FOR ABOVE-NORMAL PRECIPITATION FROM THE PACIFIC NORTHWEST
EAST TO THE GREAT LAKES IS EITHER SUPPORTED BY LA NINA COMPOSITES OR THE
CALIBRATED NMME.  PROBABILITIES FOR BELOW- AND ABOVE-NORMAL PRECIPITATION ARE
MODEST DUE TO LIMITED SKILL INHERENT IN A MONTHLY OUTLOOK AT THIS TIME LEAD.

THE HIGHEST ODDS FOR ABOVE-NORMAL TEMPERATURES ACROSS ALASKA ARE FORECAST FOR
AREAS OF THE STATE ADJACENT TO THE BERING AND CHUKCHI SEAS WHERE SEA SURFACE
TEMPERATURE ANOMALIES ARE AVERAGING AS MUCH AS 1.5 DEGREES C ABOVE NORMAL.
ENHANCED ODDS FOR BELOW-NORMAL TEMPERATURES FORECAST ACROSS PARTS OF SOUTHEAST
MAINLAND ALASKA AND THE ALASKA PANHANDLE ARE BASED ON THE MONTHLY CFS
TEMPERATURE FORECAST. THE FAVORED AREAS OF BELOW- AND ABOVE-NORMAL
PRECIPITATION ACROSS ALASKA ARE CONSISTENT WITH THE TEMPERATURE OUTLOOK AND
SUPPORTED BY THE WEEKS 3-4 CFS AND ECMWF PRECIPITATION FORECASTS ALONG WITH THE
MONTHLY CFS PRECIPITATION FORECAST.


FORECASTER: BRAD PUGH


THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING
THE WORLD METEOROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3
COMPLETE DECADES AS THE CLIMATE REFERENCE PERIOD.  THE PROBABILITY ANOMALIES
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS.



AN UPDATED MONTHLY OUTLOOK... FOR DEC WILL BE ISSUED ON THU NOVEMBER 30 2017


THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.

$$

NOAA/ National Weather Service
National Centers for Environmental Prediction
Climate Prediction Center
5200 Auth Road
Camp Springs, Maryland 20746
Climate Prediction Center Web Team
Page last modified: January 17, 2006
Disclaimer
Information Quality
Credits
Glossary
Privacy Policy
Freedom of Information Act
About Us
Career Opportunities