PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EDT THU MAY 17 2018 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS ENSO NEUTRAL CONDITIONS ARE EXPECTED INTO SUMMER 2018 WITH A GROWING CHANCE OF EL NINO BY FALL AND WINTER 2018-19. THE JUNE-AUGUST (JJA) 2018 TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES OVER MUCH OF THE CONTIGUOUS UNITED STATES (CONUS), THE EXCEPTION BEING THE VICINITY THE CENTRAL AND NORTHERN PLAINS AND THE MIDWEST, WHERE EQUAL CHANCES (EC) OF BELOW, NEAR, AND ABOVE NORMAL TEMPERATURES ARE FAVORED. THE GREATEST PROBABILITIES REACH OR EXCEED 60% ACROSS PORTIONS OF THE SOUTHWEST. ABOVE-NORMAL TEMPERATURES ARE LIKEWISE FAVORED OVER ALASKA, WITH THE LOWEST PROBABILITIES OVER CENTRAL MAINLAND ALASKA. THE JJA 2018 PRECIPITATION OUTLOOK FAVORS ABOVE NORMAL PRECIPITATION OVER MOST OF MAINLAND ALASKA AND MUCH OF THE EASTERN CONUS. ABOVE NORMAL RAINFALL IS ALSO FAVORED OVER PARTS OF THE CENTRAL AND SOUTHERN ROCKIES WHILE BELOW NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE NORTHWEST. IN SUBSEQUENT LEADS THE INCREASED ODDS OF EL NINO ARE FACTORED INTO THE TEMPERATURE AND PRECIPITATION OUTLOOKS. GENERALLY, THIS IS MANIFEST IN TERMS OF PROBABILITIES BEING SHIFTED TOWARD WETTER AND COOLER OUTCOMES ACROSS THE SOUTHERN TIER OF THE U.S. IN THE FALL AND WINTER RELATIVE TO PREVIOUS OUTLOOKS. LIKEWISE, ODDS OF ABOVE NORMAL TEMPERATURES ARE SLIGHTLY INCREASED ACROSS THE NORTHERN U.S., ESPECIALLY FROM SON THROUGH JFM. EQUAL CHANCES (EC) ARE FORECAST IN AREAS WHERE CLIMATOLOGICAL PROBABILITIES ARE INDICATED FOR SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED PRECIPITATION AMOUNTS. 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 MARGINALLY BELOW AVERAGE SEA SURFACE TEMPERATURES (SSTS) CONTINUED ACROSS MUCH OF THE CENTRAL AND EASTERN EQUATORIAL PACIFIC OCEAN; THE LATEST WEEKLY NINO 3.4 VALUE IS -0.1 C. POSITIVE HEAT CONTENT ANOMALIES CONTINUE AT DEPTH, IN PART DUE TO THE INFLUENCE OF A DOWNWELLING KELVIN WAVE. OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES AVERAGED OVER THE PAST MONTH DEPICT ONLY SLIGHTLY ENHANCED CONVECTION OVER PARTS OF THE MARITIME CONTINENT, AS LA NINA CONDITIONS CONTINUE TO WANE. SUPPRESSED CONVECTION WAS OBSERVED OVER THE EQUATORIAL CENTRAL AND EASTERN PACIFIC, CONSISTENT WITH REMNANT LA NINA CONDITIONS. LOW-LEVEL WIND ANOMALIES WERE OF LOW AMPLITUDE DURING THE PAST 30 DAYS, CONSISTENT WITH A GRADUAL RETURN TOWARD ENSO-NEUTRAL CONDITIONS. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION (CON) FORECAST FOR THE NINO 3.4 REGION PREDICTS A GRADUAL INCREASE IN ANOMALY VALUES TO ABOUT +0.5 C BY SON WITH A PEAK OF ~0.9 C IN DJF 2018-19. THE CON IS HEAVILY INFLUENCED BY THE SST CONSTRUCTED ANALOG AND THE MARKOV MODEL, BOTH OF WHICH PREDICT AN EL NINO OF MODERATE STRENGTH IN WINTER. THE CFS REMAINS ON THE COOLER SIDE OF THE DYNAMICAL MODEL ENVELOPE, AND THE BULK OF NMME CONSTITUENT MEMBERS FAVOR A NOMINAL EL NINO EVENT; THE NMME ENSEMBLE MEAN APPROACHES +0.7 C BY DECEMBER. THE CPC-IRI CONSENSUS STRONGLY FAVORS ENSO-NEUTRAL IN THE SHORT TERM, WITH ODDS OF EL NINO INCREASING TO 49% BY NDJ AND DJF. THIS APPEARS TO BE ON THE CONSERVATIVE SIDE RELATIVE TO THE OBJECTIVE GUIDANCE; THE CON DEPICTS A 70% CHANCE OF EL NINO IN DJF. THE ECMWF CONTINUES TO FAVOR EL NINO DEVELOPMENT BY SON IN ITS LATEST RUN. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS CONTINUING A TREND THAT STARTED LAST MONTH, THE INCREASING ODDS OF EL NINO WEIGH HEAVILY ON CHANGES MADE TO BOTH THE TEMPERATURE AND PRECIPITATION OUTLOOKS RELATIVE TO LAST MONTH, ESPECIALLY FOR THE FALL AND WINTER SEASONS. TO AN EXTENT THE NMME REFLECTS THESE INCREASED ODDS OF EL NINO, AS SEEN IN ITS SON AND OND PRECIPITATION FORECASTS. A RELATIVELY NEW TOOL IN OUR SUITE IS THE CBAM TOOL, OR CALIBRATION, BRIDGING, AND MERGING FORECAST TOOL. THIS USES A BAYESIAN APPROACH TO 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 ENSO-OCN STATISTICAL MODEL, AS WELL AS THE SST-CA, ALSO REFLECT THE TILT TOWARD EL NINO OVER THE COMING SEASONS, AND ARE THE MOST HEAVILY USED STATISTICAL TOOLS IN THIS OUTLOOK. THE STATISTICAL GUIDANCE AND DYNAMICAL GUIDANCE ARE AGAIN IN BROAD AGREEMENT THIS MONTH, AS BOTH SEEM TO DERIVE MUCH OF THE SIGNAL FROM ENSO AND LONG-TERM TRENDS. FOR WARM-SEASON FORECASTS ISSUED THIS TIME OF YEAR, ANOMALOUS SOIL MOISTURE CAN BE IMPORTANT DUE TO ITS IMPACT ON THE NEAR-SURFACE ENERGY BUDGET. AREAS OF ANOMALOUSLY WET SOILS CURRENTLY INCLUDE MUCH OF THE GREAT LAKES AREA, EXTENDING SOUTHWESTWARD TO THE LOWER MISSISSIPPI VALLEY. DROUGHT-RIDDEN AREAS OF THE SOUTHERN HIGH PLAINS AND SOUTHWEST HAVE ANOMALOUSLY DRY SOILS AT PRESENT. PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2018 TO JJA 2019 TEMPERATURE THE TEMPERATURE OUTLOOK FOR JJA IS LARGELY UNCHANGED FROM LAST MONTH, WITH ONLY MINOR CHANGES TO ACCOUNT FOR THE LATEST DYNAMICAL AND STATISTICAL GUIDANCE. LONG TERM TRENDS ACCOUNT FOR THE FAMILIAR U-SHAPE OVER THE CONUS, WHILE A SLIGHT INCREASE IN THE ODDS OF EL NINO DEVELOPMENT DURING JJA HAVE SOME SLIGHT COOLING AFFECT OVER THE EASTERN HALF OF CONUS, THOUGH THIS WAS ACCOUNTED FOR IN THE FORECAST ISSUED LAST MONTH AS WELL. THE STATISTICAL AND DYNAMICAL GUIDANCE AGREE ON INCREASING COVERAGE OF PROBABILITIES FAVORING ABOVE NORMAL TEMPERATURES OVER THE CONUS AS THE FORECAST PROGRESSES THROUGH LATE SUMMER AND EARLY FALL. BY SON, HOWEVER, SOME CHANGES WERE MADE TO EMPHASIZE THE INCREASING CHANCES OF EL NINO DEVELOPMENT. AREAS IN WHICH EQUAL CHANCES ARE FORECAST ARE EXPANDED ACROSS THE SOUTHEAST, WHILE PROBABILITIES FAVORING ABOVE NORMAL TEMPERATURES ARE INCREASED ACROSS THE NORTHERN TIER OF THE CONUS. TEMPERATURE PROBABILITIES FOR ALASKA LARGELY REFLECT LONG-TERM TRENDS, THOUGH ODDS FAVORING ABOVE NORMAL TEMPERATURES ARE INCREASED DURING THE COLD SEASON ALONG THE SOUTHERN AND SOUTHEASTERN COASTS DUE TO POTENTIAL ENSO IMPACTS. BY SPRING 2019, THE TEMPERATURE FORECAST REVERTS BACK TO LONG-TERM TRENDS, AND THIS CONTINUES THROUGH JJA 2019. PRECIPITATION THE PRECIPITATION OUTLOOK FOR JJA 2018 CONTAINS SOME CHANGES FROM THAT ISSUED LAST MONTH. OVER THE ROCKIES AND SOUTHWEST, CHANGES WERE MADE TO REFLECT THE LATEST GUIDANCE AND BETTER ACCOUNT FOR THE TILT TOWARD EL NINO RELATIVE TO CLIMATOLOGY, ESPECIALLY LATE IN THE SEASON. ABOVE NORMAL RAINFALL IS NOW FAVORED OVER PARTS OF THE ROCKIES WHERE THE VARIOUS TOOLS ARE IN THE BEST AGREEMENT. OVER SOUTHERN ARIZONA AND NEW MEXICO, EQUAL CHANCES IS NOW DEPICTED GIVEN THE LACK OF DYNAMICAL MODEL SKILL AND NO CLEAR SIGNALS TO INDICATE THAT EARLY MONSOON ONSET IS LIKELY. ABOVE(BELOW) NORMAL RAINFALL IS FAVORED OVER THE EASTERN CONUS (PACIFIC NORTHWEST) WHERE LONG-TERM TRENDS ARE PROMINENT. AT LATER LEADS, THE LARGEST CHANGE IS THE INTRODUCTION OF PROBABILITIES FAVORING ABOVE NORMAL PRECIPITATION OVER THE SOUTH-CENTRAL AND SOUTHEASTERN CONUS, CONSISTENT WITH THE NMME (ESPECIALLY THE CBAM) AND THE ENSO-OCN STATISTICAL MODEL. AT THIS TIME, PROBABILITIES FAVORING BELOW NORMAL PRECIPITATION ACROSS THE NORTHERN ROCKIES AND OHIO VALLEY, FOR EXAMPLE, WERE NOT INTRODUCED DUE TO THE FACT THAT A WEAK EL NINO TILT AND LONG-TERM TRENDS TEND TO DESTRUCTIVELY INTERFERE, SO EQUAL CHANCES IS DEPICTED (OF COURSE THIS WOULD ACTUALLY FAVOR THE MIDDLE TERCILE, BUT WHATEVER). BY FMA AND MAM EQUAL CHANCES IS INDICATED ACROSS THE CONUS, WITH LONG-TERM TRENDS PROVIDING A SMALL TILT TOWARD ABOVE NORMAL PRECIPITATION OVER ALASKA. DURING AMJ THROUGH JJA 2019, LONG-TERM TRENDS AS CAPTURED BY THE CON AND THE ENSO-OCN TOOLS ARE UTILIZED TO FAVOR ABOVE(BELOW) NORMAL PRECIPITATION ACROSS THE EASTERN (NORTHWESTERN) CONUS. FORECASTER: STEPHEN BAXTER 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 JUN 21 2018 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$