PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300PM EDT TUESDAY SEP 30 2014 30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2014 THE UPDATED OCTOBER 2014 OUTLOOK UTILIZES SHORT, MEDIUM AND EXTENDED RANGE GUIDANCE FOR THE FIRST HALF OF OCTOBER, IN ADDITION TO AVAILABLE LONGER TERM CLIMATE INDICATORS AS WELL AS THE CFS. THE UPDATED OUTLOOK IS LARGELY UNCHANGED FROM THE HALF MONTH LEAD FORECAST, ALTHOUGH THERE ARE SOME DIFFERENCES, AND THIS IS ALSO NOT TO SAY THAT DIFFICULT QUESTIONS DON'T REMAIN. FOR THE TEMPERATURE OUTLOOK, THE BIGGEST CHANGES IS REMOVAL (INCLUSION) OF FAVORED BELOW NORMAL TEMPERATURES IN THE SOUTHWEST (UPPER MIDWEST). GUIDANCE SUGGESTS RIDGING ACROSS THE WESTERN CONUS DURING THE FIRST HALF OF OCTOBER, SO AN OVERALL WARMER AND DRIER THAN AVERAGE SCENARIO IS MORE LIKELY ACROSS THE SOUTHWEST THAN ANTICIPATED AT HALF MONTH LEAD. HEAVY RAINFALL DURING AUGUST IN PARTS OF THE SOUTHWEST, CONSIDERED FOR THE FORECAST OF BELOW NORMAL TEMPERATURES IN THE MID SEPTEMBER OUTLOOK, HAS NOT BEEN AND LIKELY WON'T BE A FACTOR IN OCTOBER TEMPERATURES. EXTENDED RANGE MODEL GUIDANCE FAVORS A COOLER THAN AVERAGE FIRST HALF OF THE MONTH AND SO ELEVATED PROBABILITIES ARE NOW INDICATED ACROSS THE UPPER MIDWEST, ALTHOUGH PROBABILITIES ARE MODEST. CFS COMPLETE MONTH FORECASTS DO NOT CONTRADICT THIS AREA AT THE CURRENT TIME. OTHER CHANGES TO THE TEMPERATURE OUTLOOK FROM THE MID-MONTH FORECAST INCLUDE AN INCREASE IN PROBABILITIES AND COVERAGE ACROSS THE WESTERN QUARTER OF THE CONUS WHERE SHORT, MEDIUM AND EXTENDED RANGE GUIDANCE, AS WELL AS THE CFS, CONTINUES TO FAVOR ABOVE NORMAL MONTHLY MEAN TEMPERATURES. SOME MODEL GUIDANCE ALSO SHOWS COOLER CONDITIONS FOR PORTIONS OF INTERIOR EASTERN ALASKA DURING THE FIRST HALF OF OCTOBER SO EQUAL CHANCES (EC) IS NOW SHOWN IN THIS REGION TO ACCOUNT FOR SOME OF THIS UNCERTAINTY FOR THE MONTH AS A WHOLE. THE CHALLENGE FOR PRECIPITATION IN THE UPDATE IS ACROSS THE SOUTHWEST CONUS, WHERE IN THE ORIGINAL OUTLOOK, ABOVE MEDIAN PRECIPITATION WAS FAVORED FOR MUCH OF THE FOUR CORNERS REGION FOR A FEW REASONS, INCLUDING POTENTIAL CONTINUATION OF FREQUENT MOISTURE SURGES FROM AN ACTIVE EAST PACIFIC TROPICAL CYCLONE SEASON. HOWEVER, MODEL GUIDANCE FOR THE FIRST HALF OF OCTOBER SHOWS A LIKELY BELOW MEDIAN PRECIPITATION SCENARIO AS A STRONG COLD FRONT WILL CROSS THE SOUTHWEST AND USHER IN DRIER CONDITIONS THE FIRST WEEK OF OCTOBER, WHILE FORECASTS FOR WEEK-2 CONTINUE TO INDICATE BELOW MEDIAN PRECIPITATION. CONSEQUENTLY, THE REGION OF ABOVE MEDIAN PRECIPITATION IS REDUCED IN COVERAGE ALONG WITH SOMEWHAT LOWER PROBABILITIES TO THE FAR SOUTHWEST CONUS. POSITIVE SSTS, REMAINING POTENTIAL FOR MOISTURE SURGES FROM ONGOING EAST PACIFIC TROPICAL CYCLONES AND ELEVATED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION IN THE ENSEMBLE GFS WEEK-2 FORECASTS AND THE CFS. OTHER CHANGES INCLUDE REDUCING COVERAGE OF ABOVE MEDIAN PRECIPITATION ACROSS SOUTHERN ALASKA TO FOCUS PRIMARILY ON THE ALASKA PANHANDLE WHERE MODEL GUIDANCE OVER THE NEXT TWO WEEKS INDICATES THE STRONGEST SIGNAL. ALSO, THERE IS INCREASED COVERAGE FOR BELOW MEDIAN PRECIPITATION FOR THE PACIFIC NORTHWEST AND CALIFORNIA AS SHORT, MEDIUM AND EXTENDED RANGE GUIDANCE FAVOR BELOW MEDIAN PRECIPITATION. THE ABOVE-MEDIAN PRECIPITATION ACROSS THE UPPER MIDWEST AND GREAT LAKES REMAINS WITH AN INCREASE IN COVERAGE AS EXTENDED RANGE GUIDANCE AND THE CFS CONTINUE TO SUPPORT THIS HIGHLIGHTED REGION. THE MJO REMAINS LARGELY UNORGANIZED AND IS NOT A SUBSTANTIAL FACTOR IN THE UPDATED OUTLOOK. ------- PREVIOUS DISCUSSION FROM SEPTEMBER 18 -------------------------------- THROUGH THE EARLY PORTION OF SEPTEMBER, RECENT ATMOSPHERIC AND OCEANIC CONDITIONS CONTINUE TO INDICATE ENSO NEUTRAL CONDITIONS. AFTER A SLIGHT PAUSE DURING LATE JULY AND EARLY AUGUST, SEA SURFACE TEMPERATURES (SST) ACROSS THE EQUATORIAL CENTRAL PACIFIC OCEAN ARE AGAIN SHOWING AN UPWARD TREND WITH ANOMALIES AVERAGED ACROSS THE NINO3.4 REGION NOW NEAR +0.5 DEGREES C THIS PAST WEEK. EQUATORIAL OCEAN TEMPERATURES FROM THE SURFACE TO 300 M DEPTH ALSO INDICATE A RESERVOIR OF ABOVE AVERAGE OCEAN TEMPERATURES OVER MUCH OF THE CENTRAL PACIFIC OCEAN WITH THE GREATEST DEPARTURES CENTERED NEAR 100 M DEPTH FROM 170W TO 110W. STATISTICAL AND DYNAMICAL MODEL FORECASTS FOR NINO3.4 SST CONTINUE TO INDICATE PRIMARILY A WEAK EL NINO EVENT PEAKING IN LATE AUTUMN OR EARLY WINTER. THE OCTOBER OUTLOOK DID TAKE INTO CONSIDERATION POTENTIAL EL NINO CONDITIONS, MAINLY FOR ADDITIONAL SUPPORT TO OTHER FORECAST GUIDANCE. OTHER RECENT CLIMATE CONDITIONS OR FACTORS CONSIDERED FOR THE OCTOBER OUTLOOK INCLUDED POSITIVE SST ANOMALIES IN PROXIMITY TO MOST AREAS OF COASTAL ALASKA AND THE U.S. WEST COAST, AS WELL AS BELOW NORMAL ARCTIC SEA ICE ALONG THE NORTH SLOPE OF ALASKA. SOIL MOISTURE CONDITIONS ACROSS THE FAR WEST AND SOUTHWEST ALSO PLAYED A ROLE IN THE OUTLOOK. THE CURRENT WEAK MJO ACTIVITY WAS CONSIDERED FOR THE OCTOBER OUTLOOK ALTHOUGH TELECONNECTIONS DURING THIS TIME OF THE YEAR ARE DIFFICULT TO ASSESS AND THIS PLAYED A MINOR ROLE. MODEL GUIDANCE FROM THE CFS, NMME AND IMME WERE UTILIZED AS WELL IN PREPARING THE INITIAL OCTOBER OUTLOOK. MORE TRADITIONAL STATISTICAL FORECAST TOOLS OFFERED LITTLE SIGNAL OTHER THEN FOR TEMPERATURE IN ALASKA AND THE NORTHEAST CONUS. THE OCTOBER TEMPERATURE OUTLOOK INDICATES AN INCREASED LIKELIHOOD FOR ABOVE-NORMAL MONTHLY MEAN TEMPERATURES FOR THE ENTIRE STATE OF ALASKA AND THE WEST COAST STATES. FOR ALASKA, THE OUTLOOK IS BASED ON SEVERAL FACTORS THAT INCLUDE A GENERAL CONSENSUS AMONGST THE DYNAMICAL MODEL GUIDANCE FOR ABOVE-NORMAL UPPER-LEVEL HEIGHTS, ESPECIALLY FROM THE CFS, STRONGLY POSITIVE SST ANOMALIES IN NEIGHBORING WATERS AND BELOW NORMAL ARCTIC SEA ICE ALONG THE NORTH COAST. CONSISTENT RUN-TO-RUN FORECAST RIDGING BY THE CFS, CONTINUED DRY SOIL MOISTURE CONDITIONS AND ABOVE NORMAL COASTAL SSTS ARE THE BASIS FOR THE FORECAST FOR THE WEST COAST STATES. A COMBINATION OF EL NINO CONSIDERATIONS, POTENTIAL ANTECEDENT WETNESS FROM ABOVE AVERAGE SEPTEMBER RAINFALL AND FAVORED ABOVE-MEDIAN PRECIPITATION DURING OCTOBER ARE THE BASIS FOR ELEVATED ODDS OF BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTHWEST, CENTRAL ROCKIES AND CENTRAL HIGH PLAINS. DYNAMICAL MODEL GUIDANCE OF THE NMME AND IMME AND PARTICIPANT MEMBERS FAVOR ELEVATED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR AREAS IN THE GREAT BASIN AND FOR AN AREA FROM EAST TEXAS NORTH AND EAST TO INCLUDE THE MID-ATLANTIC AND NORTHEAST. THE MONTHLY OUTLOOK FOR OCTOBER 2014 INDICATES A GREATER THAN NORMAL LIKELIHOOD OF ABOVE-MEDIAN PRECIPITATION FOR MUCH OF THE SOUTHWEST AND CENTRAL ROCKIES, SOUTHERN ALASKA (INCLUDING THE PANHANDLE) AND FOR THE UPPER MIDWEST AND WESTERN GREAT LAKES REGION. BELOW MEDIAN MONTHLY PRECIPITATION AMOUNTS ARE MOST LIKELY FOR PARTS OF THE PACIFIC NORTHWEST. IN THE SOUTHWEST CONUS, MODEL FORECASTS CONTINUE TO INDICATE A CONTINUATION OF THE PATTERN THAT HAS OCCURRED OFTEN THIS SUMMER TO DATE, NAMELY AN ENHANCED ITCZ, ACTIVE TROPICAL CYCLONE SEASON AND FREQUENT MOISTURE SURGES INTO THE SOUTHWEST CONUS. IT IS DIFFICULT TO ARGUE AGAINST THIS CONTINUING INTO OCTOBER GIVEN REMAINING ABOVE NORMAL SSTS IN THE REGION AND CONTINUED FREQUENT TROPICAL CYCLONE DEVELOPMENT. TWO OTHER HIGHLIGHTED AREAS, ABOVE-MEDIAN (BELOW-MEDIAN) MONTHLY PRECIPITATION TOTALS FOR SOUTHERN ALASKA (PACIFIC NORTHWEST) ARE SHOWN IN A CONSENSUS OF THE MODEL GUIDANCE CONSISTENT WITH A MEAN TROUGH-RIDGE PATTERN ACROSS THE NORTH PACIFIC - WESTERN NORTH AMERICA REGION AS WELL AS COMPOSITES BASED ON EL NINO CONDITIONS FOR OCTOBER. FAVORED ABOVE MEDIAN PRECIPITATION IN THE UPPER MIDWEST REGION IS BASED LARGELY ON MODEL GUIDANCE WHICH SHOWS A TREND TOWARD TROUGHING AND ENHANCED PRECIPITATION IN THIS AREA. IF THE MJO REMAINS ACTIVE, WHICH IS UNCERTAIN, IT WOULD TEND TO ALSO FAVOR ABOVE MEDIAN PRECIPITATION IN THIS AREA LATER IN OCTOBER. IN AREAS WHERE CLIMATE SIGNALS ARE WEAK SUCH THAT THE LIKELIHOODS OF MONTHLY MEAN TEMPERATURES OR MONTHLY ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES (EC) IS INDICATED. THE MAIN FACTORS THAT USUALLY INFLUENCE THE MONTHLY CLIMATE OUTLOOK INCLUDE: 1) EL NINO AND LA NINA - WHICH COMPRISE ENSO. IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM THREE OR MORE DECADES INTO EL NINO, NEUTRAL AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN COMPUTING ANOMALIES. THESE ARE CALLED "COMPOSITES" AND USED AT TIMES TO SUBJECTIVELY MODIFY THE FORECAST. 2) TRENDS - APPROXIMATED BY THE OCN TOOL AS THE DIFFERENCE BETWEEN THE MOST RECENT 10-YEAR MEAN OF TEMPERATURE OR 15-YEAR MEAN OF PRECIPITATION FOR A GIVEN LOCATION AND TIME OF YEAR AND THE 30-YEAR CLIMATOLOGY PERIOD (CURRENTLY 1981-2010). 3) THE TROPICAL 30-60 DAY OSCILLATION - CALLED THE MADDEN JULIAN OSCILLATION (MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 4) THE ARCTIC OSCILLATION (AO), THE SIMILAR NORTH ATLANTIC OSCILLATION (NAO), AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING BOREAL WINTER AND ARE GENERALLY CONSIDERED TO HAVE LOW PREDICTABILITY. 5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE VARIABILITY AFFECTING THE TROPICS AND THE NORTH PACIFIC AND NORTH AMERICAN REGIONS, BUT WHICH VARIES ON A MUCH LONGER TIME-SCALE THAN ENSO. 6) PERSISTENTLY DRY OR WET SOILS IN THE SPRING AND SUMMER AND SNOW AND ICE COVER ANOMALIES IN THE WINTER. THESE FACTORS TEND TO PERSIST FOR LONG PERIODS AND ACT AS A KIND OF MEMORY IN THE CLIMATE SYSTEM. 7) STATISTICAL FORECAST MODELS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOG (CA), AND ENSEMBLE CCA (ECCA). 8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM VERSION 2 (CFS) AND FOR THE ZERO-LEAD UPDATE FORECASTS THE NCEP GLOBAL ENSEMBLE FORECAST SYSTEM (GEFS). AN EXPERIMENTAL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE (NMME), COMPRISED OF SEVERAL DYNAMICAL MODELS IS ALSO USED. FORECASTER: JON GOTTSCHALCK 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 NOV ... WILL BE ISSUED ON THU OCT 16 2014 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$