907  
FXUS05 KWBC 211231  
PMD90D  
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.  

 
 
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