90 Day Narrative

883 
FXUS05 KWBC 171231
PMD90D
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.
$$