PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
CLIMATE PREDICTION CENTER NCEP
NATIONAL WEATHER SERVICE  WASHINGTON D.C.
3 PM EST THURSDAY NOV 15 2001
  
30-DAY OUTLOOK DISCUSSION FOR DECEMBER 2001
  
ENSO-NEUTRAL CONDITIONS ARE EXPECTED TO FAVOR BELOW-AVERAGE TEMPERATURES OVER
THE NORTHEASTERN QUADRANT OF THE COUNTRY WELL INTO THE WINTER SEASON--
ALONG WITH CONSIDERABLE INTRA-SEASONAL VARIABILITY IN THE TEMPERATURE AND
PRECIPITATION PATTERNS OVER LARGE PORTIONS OF THE U.S.  THE TIMING OF THESE
FLUCTUATIONS IS CRUCIAL TO THE DECEMBER 2001 OUTLOOK AND IS LIKELY TO BE
IMPACTED BY THE PHASE AND AMPLITUDE OF THE MADDEN-JULIAN OSCILLATION (MJO).
THE MJO HAS BEEN STRONG SINCE MAY AND HAS AVERAGED A PERIODICITY OF
APPROXIMATELY 40-50 DAYS. A RECENT PHASE-REVERSAL OF THIS OSCILLATION HAS
CONTRIBUTED TO THE DRAMATIC WARM-UP ACROSS MUCH OF THE UNITED STATES AND
SOUTHERN CANADA OBSERVED SINCE LATE OCTOBER.   BASED ON A LINEAR EXTRAPOLATION
IT IS EXPECTED THAT THE MJO WILL FAVOR COOLER-THAN NORMAL CONDITIONS OVER MUCH
OF THE CENTRAL AND EASTERN U.S. THROUGH APPROXIMATELY THE FIRST WEEK IN DECEMBER
TRANSITIONING TO A WARM-UP IN THESE REGIONS DURING THE LAST TWO WEEKS OF DECEMBER.  
           .         .         .         .         .         .         .         . 
REGARDING THE MONTHLY MEAN TEMPERATURE ANOMALIES THERE IS A CONSENSUS AMONG THE
STATISTICAL AND DYNAMICAL TOOLS FOR ABOVE-AVERAGE TEMPERATURES IN THE SOUTHWEST
AND CALIFORNIA DURING DECEMBER.  THIS FORECAST IS CONSISTENT WITH THE NDJ
SEASONAL OUTLOOK ISSUED 18 OCT. 2001 AND WITH THE DJF SEASONAL OUTLOOK ISSUED
15 NOV 2001.  A SMALLER REGION OF EXPECTED ANOMALOUS WARMTH INDICATED FOR
SOUTHERN FLORIDA COMES FROM OCN AND IS CONSISTENT WITH RECENT TRENDS FOR RIDGING
TO SETTLE OVER THE SOUTHEASTERN PART OF THE U.S.  FOR THE REMAINDER OF THE
CONTIGUOUS U.S. THE STATISTICAL MODEL PREDICTIONS DO NOT INDICATE A RELIABLE 
FORECAST FOR THE MONTH.  FOR ALASKA BOTH THE CCA AND OCN SHOW SOMEWHAT STRONGER 
BUT OPPOSING TEMPERATURE SIGNALS.
                                                    
OVER MUCH OF THE U.S. EAST OF THE ROCKY MOUNTAINS THE PRIMARY FORECAST SIGNALS
FOR DECEMBER COME FROM THE ENSO-NEUTRAL COMPOSITES AND FROM LINEAR EXTRAPOLATION
OF THE MJO.  THE ENSO-NEUTRAL COMPOSITES INDICATE BELOW-AVERAGE TEMPERATURES
ACROSS THE NORTH-CENTRAL STATES DURING DECEMBER AND THIS SIGNAL IS INDICATED
PROMINENTLY ON THE CORRESPONDING NDJ SEASONAL TEMPERATURE OUTLOOK ISSUED 18 OCT 
AND ON THE DJF OUTLOOK ISSUED 15 NOV 2001.  HOWEVER IT IS PLAUSIBLE TEMPERATURES 
IN THESE REGIONS DURING THE LAST FEW WEEKS OF THE MONTH COULD BE WARMER THAN 
INDICATED BY THE COMPOSITES IN RESPONSE TO THE MJO.  GIVEN THIS SPECIFIC TIMING 
OF THE INTRA-SEASONAL FLUCTUATIONS WE WILL NOT INCLUDE IN THE DECEMBER OUTLOOK 
THE COLD ANOMALIES THAT HAVE APPEARED IN THE UPPER MIDWEST AND THE DAKOTAS IN 
RECENT MONTHLY AND SEASONAL FORECASTS.
  
FOR THE DECEMBER PRECIPITATION FORECAST THE OCN INDICATES A FAIRLY STRONG 
SIGNAL OF ABOVE-AVERAGE PRECIPITATION IN TEXAS AND OKLAHOMA.  ELSEWHERE
INCLUDING ALASKA BOTH THE CCA AND OCN INDICATE ONLY WEAK AND UNRELIABLE
SIGNALS WHICH IS CONSISTENT WITH THE EXPECTED VARIABILITY DESCRIBED ABOVE.
  
FORECASTER: G. BELL
  
NOTE - THIS CLIMATE OUTLOOK IS INTENDED FOR USE ONLY PRIOR TO THE START
OF THE VALID PERIOD.  WITHIN THE VALID PERIOD OBSERVATIONS AND SHORT
AND MEDIUM RANGE FORECASTS SHOULD BE CONSULTED.
  
NOTE - THE NEXT 0.5 MONTH LEAD-TIME MONTHLY OUTLOOK WILL BE ISSUED THURSDAY 
DECEMBER 13 2001.
  
NOTE - THE NEW 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE 
WITH THE MAY 17 2001 FORECAST RELEASE.