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. $$