PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EDT THU JUN 21 2018 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE JULY-AUGUST-SEPTEMBER (JAS) 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 AND UPPER MISSISSIPPI VALLEY. THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS PARTS OF THE GREAT BASIN AND PACIFIC NORTHWEST. THE JAS 2018 PRECIPITATION OUTLOOK FEATURES ENHANCED ODDS FOR ABOVE NORMAL PRECIPITATION ACROSS THE MID-ATLANTIC AND EXTENDING FROM SOUTHERN CALIFORNIA AND THE DESERT SOUTHWEST NORTHEAST TO THE GREAT BASIN AND CENTRAL ROCKIES. INCREASED CHANCES FOR ABOVE NORMAL PRECIPITATION ARE ALSO FORECAST ACROSS MAINLAND ALASKA AND THE ALEUTIANS. BELOW-NORMAL PRECIPITATION IS FAVORED ACROSS THE WESTERN GULF COAST, LOWER MISSISSIPPI VALLEY, 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. CHANCES FOR ABOVE NORMAL PRECIPITATION HAVE INCREASED ACROSS THE SOUTHERN TIER OF THE CONUS, COMPARED TO PREVIOUS OUTLOOKS. ODDS FOR ABOVE NORMAL TEMPERATURES CONTINUE TO INCREASE DURING THE WINTER 2018-19, FROM THE PACIFIC NORTHWEST EAST TO THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY. 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 MAY. THE OBSERVED WEEKLY SSTS, CENTERED ON JUNE 13, FEATURE POSITIVE ANOMALIES OF MORE THAN 0.5 DEGREE C FROM 140-100 DEGREES W AND ALSO WEST OF THE DATE LINE. POSITIVE SUBSURFACE TEMPERATURE ANOMALIES (AVERAGED ACROSS 180-100 DEGREES W) CONTINUED TO INCREASE, DUE TO ANOTHER DOWNWELLING OCEANIC KELVIN WAVE. OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES INDICATED SUPPRESSED CONVECTION FROM PAPUA NEW GUINEA EAST TO THE CENTRAL EQUATORIAL PACIFIC OCEAN FROM MAY 18 TO JUNE 12. THE WIND ANOMALIES AT THE LOWER AND UPPER-LEVELS WERE NEAR AVERAGE ACROSS THE EQUATORIAL PACIFIC. THESE ATMOSPHERIC INDICATORS ARE CONSISTENT WITH ENSO NEUTRAL CONDITIONS. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION (CON) FOR THE NINO 3.4 REGION INDICATES AN INCREASE IN ANOMALIES TO +0.5 DEGREES C BY SON WITH POSITIVE ANOMALIES PEAKING CLOSER TO 1.0 DEGREES C DURING NDJ AND DJF 2018-19. THE SST CONSTRUCTED ANALOG AND MARKOV MODEL 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 ABOVE 60 PERCENT FROM NDJ 2018-19 JFM 2019. 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 DECADAL TRENDS. PROGNOSTIC DISCUSSION OF OUTLOOKS - JAS 2018 TO JAS 2019 TEMPERATURE ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE CONUS AND ALASKA DURING JAS WITH THE HIGHEST PROBABILITIES FORECAST ACROSS THE GREAT BASIN AND PACIFIC NORTHWEST, BASED ON EXCELLENT AGREEMENT AMONG TOOLS INCLUDING A STRONG DECADAL SIGNAL. PROBABILITIES FOR ABOVE NORMAL TEMPERATURES WERE REDUCED ACROSS THE SOUTHWEST FROM THE PREVIOUS OUTLOOK DUE TO INCREASING FORECAST CONFIDENCE IN A WETTER PATTERN. ABOVE NORMAL TEMPERATURES ARE FAVORED TO INCLUDE MORE OF THE SOUTH-CENTRAL U.S. DURING JAS, COMPARED TO LAST MONTH, WITH THE CONSIDERATION OF LOW SOIL MOISTURE TO START THE OUTLOOK PERIOD ACROSS THE OZARKS REGION, A DRIER TREND IN THE SEASONAL TOOLS, AND CONSISTENCY WITH THE JULY TEMPERATURE OUTLOOK. ALSO, THE IMME INDICATES POSITIVE TEMPERATURES ANOMALIES FOR THE MIDDLE MISSISSIPPI VALLEY DURING THIS TIME PERIOD. 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. THE INCREASING CHANCES FOR EL NINO DEVELOPMENT WERE A FACTOR IN THE TEMPERATURE OUTLOOK, 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. 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 LARGELY ON TRENDS. 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 JAS, ODDS FOR ABOVE NORMAL PRECIPITATION WERE EXPANDED TO INCLUDE MORE OF THE DESERT SOUTHWEST AND SOUTHERN CALIFORNIA. 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. THE LATEST PRECIPITATION TOOLS, INDICATE LITTLE TO NO SUPPORT FOR THE INCREASED CHANCES OF BELOW NORMAL PRECIPITATION FOR FLORIDA, SO THAT WAS REMOVED FROM THE PREVIOUS OUTLOOK. 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 LOWER MISSISSIPPI VALLEY. THEREFORE, INCREASED CHANCES FOR BELOW NORMAL PRECIPITATION WERE INTRODUCED TO PARTS OF TEXAS AND THE LOWER MISSISSIPPI VALLEY FOR JAS. PRECIPITATION TOOLS REMAINED CONSISTENT FEATURING ENHANCED ODDS FOR ABOVE (BELOW) NORMAL PRECIPITATION ACROSS PARTS OF THE EASTERN U.S. (PACIFIC NORTHWEST) AND A RELATIVELY WET PATTERN FOR MUCH OF ALASKA. EL NINO PRECIPITATION COMPOSITES WERE RELIED UPON IN THE OUTLOOKS DURING THE FALL AND 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 THE SST CONSTRUCTED ANALOG. 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: BRAD PUGH 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 JUL 19 2018 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$