PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300 PM EDT MON OCT 31 2016 30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2016 THE MONTHLY UPDATE FOR NOVEMBER TAKES INTO ACCOUNT WEATHER CONDITIONS FORECAST OVER THE NEXT ONE TO WEEKS, AS WELL AS SUBSEASONAL CLIMATE SIGNALS IN THE WEEKS 2-4 TIME FRAME. BASED ON THESE FACTORS, SOME CHANGES WERE MADE TO THE 0.5-MONTH LEAD OUTLOOK ISSUED EARLIER THIS MONTH. AN AMPLIFIED RIDGE IS FORECAST TO DOMINATE THE CIRCULATION OVER THE CONUS FOR THE FIRST 7-10 DAYS OF THE MONTH, WITH MUCH ABOVE-NORMAL TEMPERATURES FORECAST OVER NEARLY THE ENTIRE CONUS. OVER THIS PERIOD, POSITIVE TEMPERATURE ANOMALIES COULD EXCEED 15 DEGREES F ACROSS PARTS OF THE NORTHERN PLAINS. THIS RIDGE IS FORECAST TO RETROGRADE DOWNSTREAM OF AMPLIFIED TROUGHING NEAR THE ALEUTIANS HEADING TOWARD MID-MONTH. THIS INTRODUCES MORE UNCERTAINTY IN THE TEMPERATURE OUTLOOK OVER THE EASTERN CONUS, WHERE NEAR- TO BELOW-NORMAL TEMPERATURES ARE POSSIBLE AT TIMES. MORE INTERESTINGLY, AN AMPLIFIED MJO EVENT IS FORECAST BY DYNAMICAL GUIDANCE OVER THE NEXT TWO WEEKS. WITH THE SUPPRESSED PHASE FORECAST OVER THE INDIAN OCEAN, THIS INCREASES THE ODDS OF A COLDER SOLUTION ON SUBSEASONAL TIME SCALES ACROSS THE CENTRAL AND EASTERN U.S. THE ECMWF FORECASTS FOR WEEK-3 AND WEEK-4, FOR EXAMPLE, SHOW BELOW-NORMAL TEMPERATURES OVER PARTS OF THE EASTERN CONUS. HOWEVER, GIVEN THE LARGE POSITIVE ANOMALIES UP FRONT, THERE IS LITTLE CHANCE THAT A PATTERN CHANGE EVOLVING DURING THE MIDDLE AND LATE PORTIONS OF THE MONTH WILL BE ABLE TO TIP THE MONTHLY MEAN OUT OF THE UPPER TERCILE, ESPECIALLY GIVEN THE LARGE UNCERTAINTY AT THESE LONGER LEAD TIMES. THE PRECIPITATION OUTLOOK IS UPDATED LARGELY TO REFLECT THE WEATHER CONDITIONS EARLY IN THE MONTH, INCLUDING LOCALLY HEAVY RAINFALL ACROSS PARTS OF THE PACIFIC NORTHWEST AND THE SOUTHERN PLAINS. BY THE START OF THE WEEK-2 PERIOD, A LARGELY DRY PATTERN IS FORECAST ACROSS THE CONUS BY THE DYNAMICAL MODELS. THE PATTERN CHANGE FAVORED BY THE MJO EXTRATROPICAL RESPONSE WOULD SUPPORT BELOW-MEDIAN PRECIPITATION ACROSS THE CENTRAL CONUS AND OHIO VALLEY. THERE IS SOME INDICATION OF ABOVE-MEDIAN PRECIPITATION LATER IN THE MONTH NEAR THE EAST COAST AS MORE PERSISTENT TROUGHING MAY DEVELOP NEAR 85W. BELOW-MEDIAN PRECIPITATION IS GENERALLY FAVORED PARTS OF THE INTERIOR WEST THROUGH THE UPPER-MIDWEST, AS WELL AS ACROSS THE SOUTHEASTERN QUARTER OF THE CONUS. THESE TWO REGIONS ARE SPLIT BY AN AREA FAVORING EQUAL CHANCES WHERE MODERATE RAINFALL IS FORECAST DURING THE FIRST FEW DAYS OF THE MONTH. THE PATTERN IN THE PACIFIC NORTHWEST MAY BECOME LESS ACTIVE WITH TIME AS THE MEAN ANOMALOUS TROUGH RETROGRADES TO NEAR THE ALEUTIANS, BUT HEAVY RAINFALL EARLY DECIDEDLY TILTS THE ODDS TOWARD ABOVE-MEDIAN PRECIPITATION. THE ALASKA OUTLOOK IS CONSISTENT WITH FORECASTS ACROSS TIME SCALES AND FAVORS ABOVE-NORMAL TEMPERATURES ACROSS THE ENTIRE STATE. ABOVE-MEDIAN PRECIPITATION IS FAVORED ACROSS THE SOUTHERN AND NORTHERN COASTS, WHILE BELOW-MEDIAN PRECIPITATION IS FAVORED ACROSS THE CENTRAL PORTIONS OF THE STATE. THE PREVIOUS DISCUSSION, ISSUED OCTOBER 20, IS BELOW: -------------------------------------------------------------------- DURING THE PAST MONTH, CONDITIONS OVER THE TROPICAL PACIFIC HAVE BECOME MORE CONSISTENT WITH A DEVELOPING LA NINA EVENT. COUPLED WITH THE CONSENSUS AMONG VARIOUS DYNAMICAL AND STATISTICAL TOOLS, ODDS ARE NOW TILTED IN FAVOR OF LA NINA OVER THE COMING MONTHS. AS A RESULT, STATISTICAL GUIDANCE THAT USES ENSO AS A PREDICTOR IS STRONGLY CONSIDERED FOR THIS OUTLOOK. MJO INDICES (CPC VELOCITY POTENTIAL AND RMM) INDICATE NO APPRECIABLE, COHERENT MJO ACTIVITY DURING THE PAST MONTH AND FORECASTS DO NOT DEPICT CLEAR, LONG TERM STRENGTHENING AT THE CURRENT TIME. THEREFORE, THE MJO DOES NOT INFLUENCE THE NOVEMBER OUTLOOK AT PRESENT. THE NOVEMBER 2016 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE PRIMARILY BASED ON CALIBRATED DYNAMICAL GUIDANCE, ALONG WITH STATISTICAL GUIDANCE THAT EMPHASIZES ENSO AND LONG-TERM TRENDS. COASTAL SST ANOMALIES ALSO PLAYED A SMALL ROLE IN THE OUTLOOK, PRIMARILY FOR AREAS NEAR ALASKA. THE NOVEMBER TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES FOR MOST OF THE FORECAST DOMAIN. THE ENSO SIGNAL AND LONG-TERM TRENDS TOGETHER PLACE THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES OVER THE SOUTHWESTERN AND SOUTH-CENTRAL U.S. EXTENDING NORTHEASTWARD THROUGH THE UPPER MIDWEST, GREAT LAKES, AND NORTHEAST. LONG-TERM TRENDS ARE STRONG OVER ALASKA. EQUAL-CHANCES OF BELOW-, ABOVE-, AND NEAR-NORMAL TEMPERATURES IS INDICATED OVER A SMALL PORTION OF INTERIOR ALASKA, THE PACIFIC NORTHWEST, AND THE FAR SOUTHEASTERN PORTION OF THE CONUS. THE CALIBRATED GUIDANCE FROM THE NMME, INITIALIZED EARLY THIS MONTH, STRONGLY SUPPORTS THIS PATTERN. MORE RECENTLY INITIALIZED GUIDANCE FROM THE CFS FAVORS A VERY WARM SOLUTION ACROSS MOST OF NORTH AMERICA. INTERESTINGLY, THIS PATTERN IS GENERALLY AN EXTENSION OF THE CURRENT WEEK-2 FORECAST, SUGGESTING A FAIRLY PERSISTENT PATTERN. RECENT WEEK 3/4 GUIDANCE GENERALLY SUPPORTS THE CONTINUATION OF THIS PATTERN THROUGH THE FIRST PART OF THE MONTH, THOUGH RECENT RUNS OF THE CFS AND THE ECMWF ENSEMBLES SUGGEST THAT SOME PATTERN CHANGE MAY EVOLVE DURING THE MIDDLE PORTION OF THE MONTH. INDEED, THEREIN LIES THE KEY UNCERTAINTY IN THE TEMPERATURE FORECAST. THE RECENT PATTERN HAS BEEN FAIRLY PERSISTENT OVER NORTH AMERICA, BUT AS THE SEASONAL CYCLE UNFOLDS, THE PATTERN IS EXPECTED TO EVOLVE ON LOW-FREQUENCY TIMESCALES TOWARD SOMETHING MORE AKIN TO THE LA NINA EXTRATROPICAL RESPONSE, WITH MORE SEASONABLE TEMPERATURES AND EVEN BELOW-NORMAL TEMPERATURES ACROSS PARTS OF THE NORTHERN CONUS. IN REALITY THIS CHANGE (IF IT HAPPENS) WILL OCCUR ACROSS A SERIES OF SYNOPTIC EVENTS, THE TIMING OF WHICH IS DIFFICULT TO CAPTURE IN A 0.5-MONTH LEAD MONTHLY FORECAST. THE PRECIPITATION OUTLOOK IS BASED LARGELY ON CORRELATIONS WITH ENSO, WHICH EVEN IN NOVEMBER BEGIN TO SHOW A FAIRLY CANONICAL LA NINA PATTERN. ABOVE-MEDIAN PRECIPITATION IS FAVORED OVER THE NORTHERN ROCKIES EXTENDING TO THE PACIFIC NORTHWEST, WHILE BELOW-MEDIAN PRECIPITATION IS FAVORED ACROSS MUCH OF THE SOUTHERN TIER OF THE CONUS. THIS PATTERN IS ALSO STRONGLY SUPPORTED BY THE CALIBRATED NMME GUIDANCE AND RECENT RUNS OF THE CFS. DURING THE LAST WEEK OF OCTOBER, ABOVE-MEDIAN PRECIPITATION IS FAVORED OVER MUCH OF THE WESTERN CONUS. HOWEVER, THERE IS LITTLE REASON TO BELIEVE THAT THIS SIGNAL WILL PERSIST OVER THE SOUTHWEST AND SOUTH-CENTRAL U.S. INTO NOVEMBER GIVEN THE LOW-FREQUENCY BACKGROUND STATE. AS WITH THE TEMPERATURE OUTLOOK, PROBABILITIES ARE MODEST ACROSS THE FORECAST DOMAIN GIVEN THE AFOREMENTIONED UNCERTAINTY. 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. THE NEXT MONTHLY OUTLOOK...FOR DEC ... WILL BE ISSUED ON THU NOV 17 2016 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$