PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EDT THU JUL 19 2018 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE AUGUST-SEPTEMBER-OCTOBER (ASO) 2018 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES ACROSS A MAJORITY OF THE FORECAST DOMAIN, ALTHOUGH EQUAL CHANCES OF BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS THE NORTHERN GREAT PLAINS. THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST FROM THE FOUR CORNERS REGION TO THE PACIFIC NORTHWEST. PROBABILITIES GREATER THAN 60 PERCENT FOR ABOVE NORMAL TEMPERATURES ARE ALSO INDICATED ALONG THE WESTERN COAST OF ALASKA AND FOR COASTAL PORTIONS OF NEW ENGLAND. THE ASO 2018 PRECIPITATION OUTLOOK FEATURES ENHANCED ODDS FOR ABOVE NORMAL PRECIPITATION FOR COASTAL PORTIONS OF THE SOUTHEAST, AS WELL AS OVER THE AREA EXTENDING FROM SOUTHERN CALIFORNIA AND THE DESERT SOUTHWEST TO THE GREAT BASIN AND CENTRAL ROCKIES. INCREASED CHANCES FOR ABOVE NORMAL PRECIPITATION ARE ALSO FORECAST ACROSS MAINLAND ALASKA. BELOW-NORMAL PRECIPITATION IS FAVORED ACROSS THE WESTERN GULF COAST, LOWER AND MIDDLE MISSISSIPPI VALLEYS, AND PACIFIC NORTHWEST. DURING THE FALL AND WINTER 2018-19, THE TEMPERATURE AND PRECIPITATION OUTLOOKS ARE CONSISTENT WITH INCREASING ODDS OF EL NINO DEVELOPMENT AND ITS TYPICAL INFLUENCES, WHILE ALSO INCORPORATING MODEL OUTPUT AND TRENDS. THE TEMPERATURE OUTLOOKS WERE MODIFIED TO BE MORE CONSISTENT WITH MODEL OUTPUT AND TRENDS OVER THE SOUTHEAST, ESPECIALLY DURING THE FALL OF 2018. FOR OUTLOOKS VALID DURING THE WINTER OF 2018-19, THE AREAS OVER THE NORTHERN GREAT PLAINS WHERE THE HIGHEST ODDS FOR ABOVE NORMAL TEMPERATURES ARE INDICATED HAVE BEEN SHIFTED WESTWARD, TO THE CORE AREA TYPICALLY ASSOCIATED WITH A MATURE EL NINO. THE PRECIPITATION OUTLOOKS ALREADY REFLECTED THE CANONICAL PATTERNS ASSOCIATED WITH EL NINO, SO LITTLE CHANGES WERE MADE. EQUAL CHANCES (EC) ARE FORECAST IN AREAS WHERE THE LIKELIHOOD OF SEASONAL MEAN TEMPERATURES OR SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE EXPECTED TO BE SIMILAR TO CLIMATOLOGICAL PROBABILITIES. 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 OCEANIC AND ATMOSPHERIC OBSERVATIONS ACROSS THE EQUATORIAL PACIFIC INDICATE ENSO-NEUTRAL CONDITIONS PERSISTED THROUGH JUNE. THE OBSERVED WEEKLY SSTS, CENTERED ON JULY 14, FEATURE POSITIVE ANOMALIES OF MORE THAN 0.5 DEGREE C FROM 160W - 100W AND ALSO WEST OF THE DATE LINE. TEMPERATURES MORE THAN 1.0 DEG C ABOVE NORMAL ARE ALSO MEASURED IN SOME SMALL POCKETS. POSITIVE SUBSURFACE TEMPERATURE ANOMALIES (FROM 130E TO 100E) CONTINUED TO INCREASE, DUE TO ANOTHER DOWNWELLING OCEANIC KELVIN WAVE. THE AMOUNT OF SUBSURFACE WARM WATER GIVES SLIGHTLY ELEVATED CONFIDENCE TO THE DEVELOPMENT ON EL NINO COMPARED TO MANY PRIOR EVENTS. OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES INDICATED SUPPRESSED CONVECTION FROM NORTHEAST OF PAPUA NEW GUINEA EAST TO THE CENTRAL EQUATORIAL PACIFIC OCEAN DURING JUNE 17 TO JULY 12. LOW-LEVEL WINDS ANOMALIES WERE WESTERLY FROM NEAR 170W TO 120W, CONSISTENT WITH A DEVELOPING EL NINO, WHILE UPPER-LEVEL WINDS WERE NEAR AVERAGE FOR THE PERIOD. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION (CON) FOR THE NINO 3.4 REGION INDICATES AN INCREASE IN TEMPERATURE ANOMALIES TO +0.5 DEGREES C BY ASO WITH POSITIVE ANOMALIES PEAKING CLOSER TO 1.0 DEGREES C DURING NDJ AND DJF 2018-19. THE SST CONSTRUCTED ANALOG, MARKOV MODEL, AND CFS INDICATE PEAK ANOMALY VALUES GREATER THAN 1.0 C THIS UPCOMING WINTER. THE CPC/IRI CONSENSUS FORECAST FAVORS THE ONSET OF EL NINO DURING THE NORTHERN HEMISPHERE FALL WITH PROBABILITIES OF EL NINO NEAR 70 PERCENT DURING NDJ AND DJF 2018-19. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE INCREASING LIKELIHOOD OF EL NINO DEVELOPMENT CONTINUES TO PLAY A MAJOR FACTOR IN THE FALL AND WINTER 2018-19 OUTLOOKS. TOOLS USED FOR THE SEASONAL OUTLOOKS INCLUDED DYNAMICAL MODEL FORECAST GUIDANCE SUCH AS THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME), THE ENSO-OCN STATISTICAL MODEL, THE SST CONSTRUCTED ANALOG MODEL, AND EL NINO COMPOSITES. A RELATIVELY NEW TOOL IN OUR SUITE IS THE CBAM TOOL, OR CALIBRATION, BRIDGING, AND MERGING FORECAST TOOL. THIS USES A BAYESIAN APPROACH TO THE NMME MODEL CONSOLIDATION AS WELL AS A HYBRIDIZATION WHEREIN EACH CONSTITUENT MODEL'S NINO 3.4 FORECAST IS BRIDGED TO THE PREDICTAND VIA LINEAR REGRESSION. THE OUTLOOKS DURING THE 2019 WARM SEASON WERE BASED PRIMARILY ON THE ENSO-OCN TOOL, WHICH INCORPORATES TRENDS AND RESIDUAL IMPACTS OF ENSO EVENTS. PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2018 TO ASO 2019 TEMPERATURE ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE CONUS AND ALASKA DURING ASO WITH THE HIGHEST PROBABILITIES FORECAST FROM THE FOUR CORNERS REGION TO THE INTERIOR PACIFIC NORTHWEST BASED ON GOOD AGREEMENT AMONG TOOLS INCLUDING A STRONG DECADAL SIGNAL. TRENDS FAVOR HIGHER ODDS IN THE FOUR CORNERS REGION, WHILE MODELS PREDICT HIGH ODDS FURTHER NORTH. PROBABILITIES FOR ABOVE NORMAL TEMPERATURES WERE REDUCED ACROSS THE NORTHERN GREAT PLAINS FROM THE PREVIOUS OUTLOOK DUE TO INCREASED UNCERTAINTY FROM THE TOOLS AS WELL AS INCREASED POTENTIAL FOR LAGGED IMPACTS FROM A RECENT WET PATTERN. ODDS FOR ABOVE NORMAL TEMPERATURES WERE INCREASED OVER MISSOURI AND KANSAS, WHERE SOILS ARE DRYING RAPIDLY DURING A RECENT WARM AND DRY PERIOD. ALSO, THE NMME AND IMME INDICATES POSITIVE TEMPERATURES ANOMALIES FOR THE MIDDLE MISSISSIPPI VALLEY DURING THIS TIME PERIOD, THOUGH THE STRONGEST NMME SIGNAL IS ACROSS THE WESTERN CONUS. EQUAL CHANCES FOR BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ARE FORECAST FOR THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY WHERE FORECAST CONFIDENCE IS LOWEST AND MODEL SKILL IS AT A MINIMUM. THE INCREASING CHANCES FOR EL NINO DEVELOPMENT WERE A FACTOR IN THE TEMPERATURE OUTLOOKS, BEGINNING IN THE FALL AND BECOMING MORE PROMINENT DURING THE WINTER 2018-19. BASED ON EL NINO COMPOSITES, PROBABILITIES FOR ABOVE NORMAL TEMPERATURES WERE INCREASED ACROSS MUCH OF MAINLAND ALASKA AND ALONG THE NORTHERN TIER OF THE CONUS WITH A DECREASE IN THE COVERAGE OF ABOVE NORMAL TEMPERATURES THROUGHOUT THE SOUTHERN TIER OF THE CONUS. THE HIGHEST ODDS FOR ABOVE NORMAL TEMPERATURES DURING EL NINO ARE TYPICALLY ACROSS THE NORTHERN INTERMOUNTAIN WEST. AN EXPECTED LACK OF SEA ICE ELEVATES CHANCES FOR ABOVE NORMAL TEMPERATURES ACROSS NORTHERN ALASKA DURING THE FALL SEASON. THE TEMPERATURE OUTLOOK AT THE LONGER LEAD TIMES IS BASED ON A BLENDING OF TRENDS AND ENSO IMPACTS. PRECIPITATION THE PRECIPITATION OUTLOOKS ARE BASED ON THE LATEST DYNAMICAL MODEL GUIDANCE, THROUGH NDJ, ALONG WITH THE TYPICAL INFLUENCES FROM EL NINO DURING THE FALL AND WINTER 2018-19. COMPARED TO THE PREVIOUS OUTLOOK FOR ASO, ODDS FOR BELOW NORMAL PRECIPITATION ACROSS THE MISSISSIPPI VALLEY ARE INCREASED, WHILE THE ODDS FOR ABOVE NORMAL PRECIPITATION OVER THE SOUTHWEST REMAIN NEARLY UNCHANGED. THIS IS CONSISTENT WITH THE NMME AND POTENTIAL RAINFALL ASSOCIATED WITH EAST PACIFIC TROPICAL CYCLONES, WHICH ARE MORE LIKELY TO AFFECT THESE AREAS DURING A DEVELOPING EL NINO. MODEL OUTLOOKS FOR ASO INDICATE INCREASED ODDS FOR BELOW NORMAL PRECIPITATION FOR THE PACIFIC NORTHWEST, THOUGH SOME STATISTICAL TOOLS DO NOT SHOW THIS SIGNAL, SO THE COVERAGE IS SMALL, WHILE OVER THE SOUTHERN ALASKA PANHANDLE THE STATISTICAL TOOLS AGREE WITH THE DYNAMICAL MODELS. THE LATEST PRECIPITATION PREDICTIONS FROM THE NMME INDICATE INCREASED CHANCES OF ABOVE NORMAL PRECIPITATION FROM THE CAROLINAS TO FLORIDA, WHILE THE CPC CON SHOWS THAT WET SIGNAL FROM THE MID-ATLANTIC TO FLORIDA. THE OUTLOOK REFLECTS THE AREA OF AGREEMENT BETWEEN THOSE TWO TOOLS. THE NMME INDICATES RELATIVELY HIGH ODDS FOR BELOW NORMAL PRECIPITATION EXTENDING FROM THE CARIBBEAN REGION WEST TO THE GULF OF MEXICO AND MUCH OF TEXAS AND THE MIDDLE MISSISSIPPI VALLEY. THEREFORE, INCREASED CHANCES FOR BELOW NORMAL PRECIPITATION WERE EXPANDED FROM THE PRIOR OUTLOOK. PRECIPITATION TOOLS REMAINED CONSISTENT FEATURING ENHANCED ODDS FOR ABOVE NORMAL PRECIPITATION ACROSS MUCH OF ALASKA. EL NINO PRECIPITATION COMPOSITES WERE RELIED UPON IN THE OUTLOOKS DURING THE WINTER SEASONS WHEN ABOVE-NORMAL PRECIPITATION BECOMES MORE LIKELY ACROSS THE SOUTHWEST, SOUTHERN GREAT PLAINS, GULF COAST STATES, AND SOUTHEAST. THE STRONGEST WET SIGNAL EXISTS ACROSS FLORIDA DURING NDJ AND DJF, WHILE A DRY SIGNAL EXISTS FROM THE GREAT LAKES SOUTH TO THE OHIO VALLEY DURING JFM AND FMA. THE PRECIPITATION OUTLOOK ACROSS ALASKA DURING THE FALL AND WINTER IS CONSISTENT WITH NMME OUTPUT AND THE ENSO-OCN TOOL. AT THE LONGER LEADS, MJJ THROUGH JAS 2019, THE TILT IN THE ODDS TOWARDS ABOVE NORMAL PRECIPITATION ACROSS PARTS OF THE CENTRAL AND EASTERN U.S. IS CONSISTENT WITH TRENDS. ALSO, THE FAVORED AREA FOR BELOW-MEDIAN PRECIPITATION ACROSS THE NORTHWESTERN CONUS DURING THESE OUTLOOK PERIODS IS RELATED TO TRENDS. FORECASTER: MATTHEW ROSENCRANS 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/LONG_RANGE/TOOLS.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/PRODUCTS/SOILMST_MONITORING/US/OUTLOOK/OUTLOOK.SHTM L (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 AUG 16 2018 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$