90 Day Narrative
416 FXUS05 KWBC 191231 PMD90D PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830AM EDT THURSDAY SEP 19 2013 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE MAIN FACTORS THAT USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE: 1) EL NINO AND LA NINA - WHICH TOGETHER COMPRISE EL NINO/SOUTHERN OSCILLATION OR ENSO. IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM 3 OR MORE DECADES INTO EL NINO, NEUTRAL, AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN COMPUTING ANOMALIES. THESE ARE CALLED "ENSO COMPOSITES", WHICH ARE 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 - SOMETIMES CALLED MADDEN JULIAN OSCILLATION (MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 4) THE NORTH ATLANTIC OSCILLATION (NAO) AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING THE COLD SEASONS. THESE PHENOMENA ARE CONSIDERED LESS PREDICTABLE ON A SEASONAL TIMESCALE THAN ENSO. 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 TOOLS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOGUE (CA) AND ENSEMBLE CCA (ECCA). 8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM (CFS). AN EXPERIMENTAL MODEL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE, COMPRISED OF SEVERAL MODELS AND DESIGNATED NMME, MAY ALSO BE USED EXPERIMENTALLY AND SUBJECTIVELY UNTIL IT IS INCLUDED INTO THE CONSOLIDATION. AN INTERNATIONAL MODEL ENSEMBLE DESIGNATED IMME IS ALSO AVAILABLE. 9) CONSOLIDATION (CON) - AN OBJECTIVE, SKILL WEIGHTED COMBINATION OF THE OCN, CCA, SMLR, ECCA, AND CFS FORECASTS IS USED AS A FIRST GUESS IN PREPARING THE FORECAST MAPS. THIS TECHNIQUE MAKES OPTIMUM USE OF THE KNOWN SKILL OF OUR FORECAST TOOLS. RECENT ATMOSPHERIC AND OCEANIC OBSERVATIONS CONTINUE TO INDICATE ENSO NEUTRAL CONDITIONS. THE OFFICIAL ENSO OUTLOOK CALLS FOR A CONTINUATION OF THE ENSO NEUTRAL STATE INTO BOREAL WINTER 2013/2014. THE OCTOBER-NOVEMBER-DECEMBER (OND) 2013 TEMPERATURE OUTLOOK INDICATES ELEVATED CHANCES FOR ABOVE-NORMAL TEMPERATURES IN MUCH OF THE WEST, THE ALASKA PANHANDLE, NEW ENGLAND, AND FOR THE NORTH SLOPE OF ALASKA. THE CONFIDENCE FOR ABOVE-NORMAL TEMPERATURES IS HIGHEST OVER PORTIONS OF ARIZONA, NEW MEXICO, AND MAINE. THE OND 2013 PRECIPITATION OUTLOOK CALLS FOR ELEVATED CHANCES OF ABOVE-MEDIAN PRECIPITATION IN NORTHERN PORTIONS OF BOTH THE ROCKIES AND HIGH PLAINS. IN AREAS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES (EC) IS SHOWN. BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE: HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS NEAR-EQUATORIAL SEA-SURFACE TEMPERATURES (SST) ARE NEAR-AVERAGE AS OF EARLY MID SEPTEMBER 2013 ACROSS THE CENTRAL AND EAST-CENTRAL PACIFIC, AND BELOW-AVERAGE IN THE EASTERN PACIFIC. IN THE MOST RECENT WEEK, SST ANOMALIES IN THE NINO 3.4 REGION ARE ZERO DEGREES CELSIUS. BUOY MEASUREMENTS INDICATE A LARGE VOLUME OF ANOMALOUSLY WARM SUB-SURFACE WATER, ABOUT +1C ANOMALY TYPICALLY, BETWEEN 50-200 METERS DEEP OVER THE WESTERN, CENTRAL AND EAST-CENTRAL EQUATORIAL PACIFIC, AND NEARER TO THE SURFACE IN THE EASTERN PACIFIC TO ABOUT 100W. LOW-LEVEL (850-HPA) TRADE WINDS REMAINED NEAR AVERAGE ACROSS THE EQUATORIAL PACIFIC, BUT THERE HAVE BEEN OCCASIONAL SHORT PERIODS OF ANOMALOUS EASTERLIES IN THE WEST PACIFIC. TROPICAL CONVECTION CONTINUES TO BE ENHANCED OVER INDONESIA AND SUPPRESSED ALONG THE EQUATOR OVER THE CENTRAL PACIFIC AND EASTWARD. COLLECTIVELY, THESE OCEANIC AND ATMOSPHERIC CONDITIONS REFLECT THE ENSO NEUTRAL STATE. PROGNOSTIC DISCUSSION OF SST FORECASTS ENSO NEUTRAL CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE NORTHERN HEMISPHERE WINTER OF 2013/14. THE CPC CONSOLIDATION OF NINO 3.4 SST FORECASTS PREDICTS ANOMALIES LIKELY RANGING FROM 0.0 TO -0.3 DEGREES C THROUGH THE REMAINDER OF 2013 AND INTO 2014. THE RANGE OF MOST DYNAMICAL AND STATISTICAL MODEL FORECASTS INCLUDED IN THE IRI PLUME, NMME AND IMME REMAINS FROM -0.3 TO +0.6 DEGREES C THROUGH EARLY 2014. A PECULIAR DICHOTOMY PERSISTS WITH MANY STATISTICAL MODELS NEUTRAL BUT A FEW TENTHS NEGATIVE, AND A LARGE MAJORITY OF DYNAMICAL MODELS NEUTRAL BUT A FEW TENTH POSITIVE. OVERALL,FORECASTS THUS FAVOR A CONTINUATION OF THE ENSO NEUTRAL STATE THROUGH AUTUMN AND WINTER. COMPARED TO LAST MONTH THE PLUME OF FORECASTS HAS NUDGED UPWARD BY 0.2 DEGREES C. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS WERE MADE CONSIDERING ENSO NEUTRAL CONDITIONS TO BE MOST LIKELY THROUGH EARLY SPRING 2014. THE FORECASTS FROM OND 2013 THROUGH FMA 2014 WERE BASED ON A COMBINATION OF STATISTICAL TOOLS AND DYNAMICAL MODEL GUIDANCE INCLUDING THE CFS, THE NMME AND THE IMME. THE CONSOLIDATION AND DECADAL TRENDS FROM THE OCN WERE CONSIDERED FOR ALL LEADS. DECADAL CLIMATE TRENDS WERE THE PRIMARY SOURCE OF PREDICTABILITY FOR THE FORECASTS AFTER FMA 2014. PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2013 TO OND 2014 TEMPERATURE COMPARED TO LAST MONTH'S RELEASE WE REMOVED SOME SIGNALS, PARTICULARLY FOR THE EXTENT OF FAVORED ABOVE AVERAGE TEMPERATURE IN THE NORTHEASTERN QUADRANT OF THE CONUS IN THE FIRST SIX LEADS. ON THE OTHER HAND ELEVATED ODDS OF ABOVE AVERAGE TEMPERATURES IN THE WEST WERE EXTENDED NORTHWESTWARD TO INCLUDE THE PACIFIC NORTHWEST AND THE ALASKA PANHANDLE. THE SEASONAL TEMPERATURE OUTLOOK FOR OND 2013 INDICATES ELEVATED CHANCES OF ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE WEST, NEW ENGLAND, AND FOR BOTH THE PANHANDLE AND NORTH SLOPE OF ALASKA. FOR THE REGIONS NOTED, THE OUTLOOK IS PRIMARILY BASED ON DYNAMICAL MODEL GUIDANCE FROM THE CFS, NMME AND IMME, IN ADDITION TO THE CONSOLIDATION (CON) TOOL. FOR THE NORTH SLOPE OF ALASKA, THE TEMPERATURE OUTLOOK IS MAINLY FROM SIGNIFICANT POSITIVE DECADAL TRENDS, PRESUMABLY RELATED TO A REDUCTION IN ARCTIC OCEAN SEA ICE COVER DURING RECENT YEARS FOR THIS SEASON. THE NEXT FOUR OUTLOOKS (NDJ 2013 THROUGH FMA 2014) ARE HEAVILY BASED ON DYNAMICAL MODEL GUIDANCE, AND THE CON TOOL. ENHANCED CHANCES FOR ABOVE-NORMAL TEMPERATURES IS CONCENTRATED IN THE WEST THROUGH JFM2014. FROM FMA 2014 ONWARD, THE TEMPERATURE OUTLOOKS ARE PRIMARILY BASED ON THE CON TOOL, WHICH TAKES LONG-TERM TRENDS INTO ACCOUNT. THERE ARE ELEVATED ODDS OF BELOW-NORMAL TEMPERATURES OVER PORTIONS OF THE PACIFIC NORTHWEST FROM MAM THROUGH AMJ 2014. THIS APPEARS TO BE DUE TO DECADAL TEMPERATURE TRENDS. FROM FMA TO JJA 2014, THERE ARE ENHANCED CHANCES FOR ABOVE-NORMAL TEMPERATURES ACROSS MUCH OF THE SOUTHERN AND PARTS OF THE EASTERN CONUS, WITH THE HIGHEST PROBABILITIES INDICATED OVER THE SOUTHWEST. FROM JAS TO SON 2014, THERE ARE ELEVATED ODDS OF ABOVE-NORMAL TEMPERATURES ACROSS MUCH OF THE SOUTHERN CONUS, THE NORTHEAST, AND FLORIDA. THIS IS BASED MOSTLY ON THE CON, AND IS ATTRIBUTED TO LONGER-TERM TEMPERATURE TRENDS. POSITIVE DECADAL TEMPERATURE TRENDS ARE SIGNIFICANT FROM AMJ - OND 2014 ACROSS FAR NORTHERN ALASKA. IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF BELOW, NEAR AND ABOVE NORMAL SEASONAL MEAN TEMPERATURES ARE INDICATED. PRECIPITATION COMPARED TO LAST MONTH'S RELEASE WE REMOVED SOME SIGNALS, PARTICULARLY FOR ENHANCED ODDS FOR ABOVE MEDIAN PRECIPITATION IN THE OHIO VALLEY IN OND. ON THE OTHER HAND ELEVATED ODDS FOR BELOW MEDIAN PRECIPITATION WERE ADDED IN THE INTERIOR SOUTHWEST FROM NDJ - MAM. THE OND 2013 PRECIPITATION OUTLOOK INDICATES AN ENHANCED LIKELIHOOD OF ABOVE-MEDIAN PRECIPITATION OVER MONTANA AND NORTHERN IDAHO. THIS FORECAST IS PRIMARILY BASED ON DYNAMICAL MODEL GUIDANCE FROM THE CFS, NMME AND IMME. THESE SAME TOOLS SUPPORT A SIMILAR PRECIPITATION FORECAST FOR MONTANA AND IDAHO FOR NDJ2013-14, BUT IN ADDITION, THERE ARE ENHANCED CHANCES OF BELOW-MEDIAN PRECIPITATION FOR THE SOUTHERN ATLANTIC COAST STATES, AND THE INTERIOR SOUTHWEST, BASED ON THE CON TOOL, WHERE DECADAL PRECIPITATION TRENDS TILT THE ODDS TOWARDS BELOW-MEDIAN IN THIS REGION THROUGH THE JFM 2014 SEASON FOR THE SOUTHEAST AND THROUGH MAM2014 FOR THE SOUTHWEST. SEASONAL PRECIPITATION SIGNALS ARE WEAK AND UNRELIABLE FOR MOST OF THE REMAINING SEASONS, EXCEPT FOR THE PACIFIC NORTHWEST IN JJA AND JAS 2014, WHERE HISTORICAL TRENDS FAVOR BELOW-MEDIAN PRECIPITATION. IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF BELOW, NEAR AND ABOVE MEDIAN SEASONAL TOTAL PRECIPITATION AMOUNTS ARE INDICATED. FORECASTER: HUUG VAN DEN DOOL THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 COMPLETE DECADES AS THE CLIMATIC 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. FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS - THEIR SKILL- AND THE FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT HTTP:/WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/DISC.HTML (USE LOWER CASE LETTERS) INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT: HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWERCASE LETTERS) NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID PERIOD. WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM RANGE FORECASTS SHOULD BE CONSULTED. THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT MONTH ON OCT 17 2013 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$