PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
830 AM EDT THU OCT 18 2018 
 
 
30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2018 
 
FORECASTS OF AUTUMN CLIMATE ARE ESPECIALLY DIFFICULT, AND THE NOVEMBER 2018 
OUTLOOK IS NO EXCEPTION. LOW-FREQUENCY CLIMATE FORCING FROM ENSO IS EXPECTED TO 
GRADUALLY INCREASE DURING THE NEXT SEVERAL WEEKS, THOUGH THIS HAS LIMITED 
APPLICATIONS TO THE CURRENT OUTLOOK, ESPECIALLY WITH RESPECT TO TEMPERATURE. 
THE MJO HAS BEEN ACTIVE OVER THE PAST SEVERAL WEEKS, BUT IS NOT EXPECTED TO 
PLAY A MAJOR ROLE DURING NOVEMBER - THIS IS DUE TO BOTH UNCERTAIN MJO FORCING 
ITSELF AS WELL AS ONLY MODEST EXTRATROPICAL TELECONNECTIONS AT THIS POINT IN 
THE SEASONAL CYCLE. THE FORECAST IS THEREFORE INFORMED FIRSTLY BY A BLEND OF 
CALIBRATED DYNAMICAL GUIDANCE FROM THE NMME AND STATISTICAL GUIDANCE THAT 
LARGELY UTILIZES LONG-TERM TRENDS. THIS IS AUGMENTED BY ADDITIONAL DYNAMICAL 
GUIDANCE FROM THE ECMWF, THE WEEKS 3-4 GUIDANCE, AND THE CURRENT EVOLUTION OF 
DYNAMICAL MODEL FORECASTS THROUGH THE EXTENDED RANGE (~DAYS 10-16) PERIOD. 
 
LONG-TERM TRENDS GENERALLY FAVOR ABOVE-NORMAL TEMPERATURES OVER MUCH OF THE 
CONUS DURING THIS TIME OF YEAR, STRETCHING FROM THE SOUTHWEST TO THE NORTHEAST, 
WITH RELATIVE WEAKNESSES IN THE NORTHWEST AND SOUTHEAST, RESPECTIVELY. AT THIS 
POINT, ENSO TELECONNECTIONS ARE NOT A MAJOR PLAYER IN THE TEMPERATURE FORECAST 
FOR TWO REASONS: THE CONVECTIVE RESPONSE TO THE DEVELOPING ENSO EVENT HAS BEEN 
SLOW TO EMERGE TO THIS POINT, AND EVEN IN THE PRESENCE OF A SUBSTANTIAL EVENT 
THE SIGNAL-TO-NOISE RATIO IS QUITE LOW FOR NOVEMBER (CORRELATIONS NEAR OR LESS 
THAN 0.2). THE CALIBRATED NMME MODEL OUTPUT FAVORS ABOVE-NORMAL TEMPERATURES 
OVER NEARLY ALL OF NORTH AMERICA, WITH THE LOWEST PROBABILITIES OVER THE 
SOUTHEASTERN QUARTER OF THE CONUS. THE CFS HAS CONSISTENTLY BEEN FORECASTING 
ABOVE-NORMAL TEMPERATURES OVER THE ENTIRE CONUS AND MUCH OF ALASKA, WITH 
BELOW-NORMAL TEMPERATURES CONFINED TO MUCH OF NORTHEASTERN CANADA. THE 
AFOREMENTIONED FACTORS POINT TO AN INITIAL 'FIRST GUESS' THAT FAVORS ENHANCED 
PROBABILITIES OF ABOVE-NORMAL TEMPERATURES OVER THE ENTIRE FORECAST DOMAIN, 
WITH THE HIGHEST PROBABILITIES OVER NORTHERN AND WESTERN ALASKA AND PARTS OF 
THE WESTERN CONUS. HOWEVER, PROBABILITIES ARE TEMPERED BY TWO MAIN FACTORS OVER 
THE CENTRAL AND EASTERN U.S. FIRST, THE ECMWF IN BOTH ITS LONG-RANGE ENSEMBLE 
SYSTEM AND EXTENDED RANGE (WEEKS 3-4) SYSTEM FAVOR NEAR- TO BELOW-NORMAL 
TEMPERATURES CENTERED OVER THE CENTRAL AND SOUTHEASTERN CONUS, AND RUN-TO-RUN 
CONTINUITY HAS BEEN GOOD IN THIS REGARD.  SECONDLY, THIS APPEARS SUPPORTED BY A 
FORECAST PATTERN CHANGE OVER THE HIGH LATITUDES TOWARD A NEGATIVE PHASE OF THE 
NAO/AO DURING THE NEXT WEEK TO 10 DAYS. THE LATEST EVOLUTION OF THE GEFS FROM 
DAYS 11 TO 16 FAVORS A CONTINUATION OF POSITIVE HEIGHT ANOMALIES OVER NORTHERN 
LATITUDES AND ANOMALOUS TROUGHING SOMEWHERE OVER THE CENTRAL/EASTERN CONUS 
HEADING INTO THE VERY BEGINNING OF NOVEMBER. THESE COMPOUNDING FACTORS LEAD TO 
A REDUCTION IN PROBABILITIES FAVORING ABOVE-NORMAL TEMPERATURES OVER MOST OF 
THE CENTRAL AND EASTERN CONUS. HOWEVER, GIVEN THE LARGE SCALE CLIMATE FACTORS 
AT PLAY, THEY ARE NOT SUFFICIENT TO REVERSE THE SIGN OF THE EXPECTED CLIMATE 
ANOMALIES. 
 
THE PRECIPITATION FORECAST FOR NOVEMBER 2018 HAS MUCH REDUCED COVERAGE COMPARED 
TO THE TEMPERATURE OUTLOOK, AS IS EXPECTED GIVEN THE LIMITED PREDICTABILITY FOR 
THIS TYPE OF FORECAST. THE FORECAST IS INFORMED BY THE DYNAMICAL MODEL 
CONSENSUS AND NINO 3.4 REGRESSIONS, WHICH JUST ABOUT REVEAL THE SAME GENERAL 
PATTERN. ABOVE-MEDIAN PRECIPITATION IS FAVORED OVER PARTS OF THE SOUTHERN TIER 
OF THE CONUS AS WELL AS MUCH OF ALASKA. A MODEST AREA DEPICTING BELOW-MEDIAN 
PRECIPITATION IS INDICATED OVER THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. 
AREAS SHOWN IN WHITE LABELED EC DEPICT A FORECAST WHERE THE PROBABILITIES FOR 
EITHER OF THREE CATEGORIES, BELOW-, NEAR- OR ABOVE-MEDIAN MONTHLY TOTAL 
PRECIPITATION ARE NOT SIGNIFICANTLY DIFFERENT FROM CLIMATOLOGICAL PROBABILITIES. 
 
FORECASTER: STEPHEN BAXTER 
 
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 NOV WILL BE ISSUED ON WED OCTOBER 31 2018 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. 
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