205  
FXUS05 KWBC 191231  
PMD90D  
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.  

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page