PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
830 AM EST THU NOV 19 2009 
 
30-DAY OUTLOOK DISCUSSION FOR DECEMBER 2009 
 
EL NINO CONTINUED TO STRENGTHEN DURING THE MONTH OF OCTOBER AND INTO EARLY 
NOVEMBER.  SEA SURFACE TEMPERATURES (SSTS) IN THE PACIFIC OCEAN ARE NOW MORE 
THAN 1.5 DEG. C ABOVE NORMAL ALONG THE EQUATOR FROM 170 E TO 120 W LONGITUDE, 
WITH ANOMALIES CLOSE TO 2 DEG. C FROM NEAR THE DATE LINE TO 130W.  SUB-SURFACE 
OCEAN TEMPERATURES IN THE EASTERN EQUATORIAL PACIFIC OCEAN ARE WELL ABOVE 
NORMAL.  THE AVERAGE HEAT CONTENT OF THE UPPER 300 METERS HAS BEEN STEADY IN 
RECENT MONTHS AFTER HAVING RETREATED SLIGHTLY FROM THEIR PEAK VALUES IN LATE 
SUMMER.  ATMOSPHERIC CONDITIONS OVER THE TROPICAL PACIFIC ARE CONSISTENT WITH 
EL NINO, WITH LOW LEVEL WESTERLY WIND ANOMALIES AND UPPER LEVEL EASTERLY WIND 
ANOMALIES OBSERVED IN OCTOBER AND EARLY NOVEMBER.  THE MEAN ATMOSPHERIC 
CONVECTION FOR OCTOBER 2009 WAS ENHANCED IN THE WEST-CENTRAL EQUATORIAL PACIFIC 
AND SUPPRESSED OVER INDONESIA.  THESE INDICATORS ARE SUGGESTIVE OF A MODERATE 
EL NINO EVENT.  MOST MODELS PREDICT THAT THE EL NINO INTENSITY WILL REMAIN 
MODERATE THROUGH DECEMBER. 
 
THE MADDEN-JULIAN OSCILLATION (MJO) HAS BEEN QUITE ACTIVE IN THE PAST FEW 
WEEKS.  THE MJO IS EXPECTED TO COMPLICATE THE ATMOSPHERIC EL NINO 
TELECONNECTIONS DURING THE MONTH OF DECEMBER.  SPECIFICALLY, THE CHANCE OF 
ABOVE MEDIAN PRECIPITATION AMOUNTS IS ELEVATED ALONG THE WEST COAST OF THE 
CONUS AS A RESULT OF THE INFLUENCE OF THE MJO EXPECTED IN THE EARLY PART OF 
DECEMBER. 
 
THE TEMPERATURE OUTLOOK FOR DECEMBER IS MOSTLY BASED ON THE CFS MODEL FORECAST 
AND EL NINO COMPOSITES FOR NDJ.  INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES 
ARE INDICATED FOR THE WESTERN U.S. EXCEPT FOR PARTS OF THE SOUTHWEST AND 
SOUTHERN ROCKIES DUE TO AN UPPER LEVEL RIDGE EXPECTED OVER WESTERN NORTH 
AMERICA ASSOCIATED WITH EL NINO.  EL NINO TELECONNECTIONS FAVOR BELOW NORMAL 
TEMPERATURES NEAR TEXAS AND PORTIONS OF THE WESTERN GULF STATES.  THE CFS 
INDICATES BELOW NORMAL TEMPERATURES THROUGHOUT MOST OF THE SOUTHEASTERN U.S., 
HOWEVER, ENSO COMPOSITES SUGGESTING BELOW NORMAL TEMPERATURES ARE LESS 
CONVINCING ALONG THE EASTERN GULF THAN THE WESTERN GULF SO EC IS INDICATED FOR 
MUCH OF THE SOUTHEAST AND EASTERN U.S.  ABOVE NORMAL TEMPERATURES ARE FAVORED 
FOR MUCH OF THE CENTRAL AND EASTERN PARTS OF ALASKA INCLUDING THE PANHANDLE. 
 
THE PRECIPITATION FORECAST IS CONSISTENT WITH ENSO COMPOSITES WITH SOME 
REVISIONS DUE TO THE CFS MODEL FORECASTS AND AN ACTIVE MJO.  EL NINO USUALLY 
INCREASES THE CHANCES OF ABOVE MEDIAN PRECIPITATION AMOUNTS FOR SOUTHERN 
CALIFORNIA.  AN ACTIVE MJO IN THE PHASE PREDICTED IN EARLY DECEMBER INCREASES 
CHANCES FOR ENHANCED PRECIPITATION AMOUNTS FARTHER NORTH ALONG THE COAST THAN 
NORMALLY EXPECTED IN EL NINO, SO ELEVATED CHANCES FOR ABOVE MEDIAN 
PRECIPITATION AMOUNTS FOR THIS DECEMBER EXTEND TO SOUTHERN OREGON.  THE MJO 
RELATED ACTIVITY FAVORS WET CONDITIONS IN THE PACIFIC NORTHWEST, CONTRADICTING 
THE DRY CONDITIONS USUALLY FAVORED IN EL NINO DECEMBERS RESULTING IN A FORECAST 
FOR EQUAL CHANCES FOR BELOW, NEAR, OR ABOVE MEDIAN PRECIPITATION AMOUNTS FOR 
COASTAL AREAS IN WASHINGTON STATE AND NORTHERN OREGON.  THE CFS INDICATES ABOVE 
MEDIAN PRECIPITATION ALONG THE ALASKAN PANHANDLE.  THE CFS PREDICTS DRY 
CONDITIONS FOR MUCH OF THE WESTERN U.S., HOWEVER, WITH THE UNCERTAINTY DUE TO 
MJO AND GENERALLY WEAK ENSO PRECIPITATION TELECONNECTIONS IN THE EARLY PART OF 
THE WINTER SEASON, PROBABILITIES FOR BELOW MEDIAN PRECIPITATION ARE ONLY 
SIGNIFICANTLY ENHANCED FOR THE NORTHERN ROCKIES WHERE THE ENSO SIGNAL FOR DRY 
IS STRONGEST.  AN ENHANCED SOUTHERN JET IN ASSOCIATED WITH EL NINO IS EXPECTED 
TO ELEVATE CHANCES FOR ABOVE MEDIAN PRECIPITATION AMOUNTS ALONG THE GULF COAST 
FROM TEXAS THROUGH FLORIDA.  THE CFS FORECASTS FOR ENHANCED PRECIPITATION IN 
FLORIDA ARE DISTINCTLY LESS CERTAIN THAN FOR THE WESTERN GULF, SO HIGHEST 
PROBABILITIES ARE FOR INDICATED FOR SOUTHERN TEXAS. 
 
 
 
FORECASTER: DAVID UNGER 
 
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). 
 
AN UPDATED MONTHLY OUTLOOK... FOR DEC WILL BE ISSUED ON MON NOVEMBER 30 2009 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. 
 
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