073  
FXUS05 KWBC 181231  
PMD90D  
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
830 AM EDT THU OCT 18 2018  
 
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS  
 
THIS SECTION OF THE SEASONAL OUTLOOK MESSAGE SUMMARIZES THE FIRST FORECAST IN  
THE SET, THE NOVEMBER-DECEMBER-JANUARY (NDJ) 2018-2019 SEASONAL OUTLOOK.  
DESCRIPTION OF THE SUBSEQUENT OUTLOOKS, CLIMATE FACTORS CONSIDERED, AND  
SPECIFIC FORECAST RATIONALE FOR ALL OUTLOOKS ARE PROVIDED IN THE LAST TWO  
SECTIONS OF THE MESSAGE.  
 
THE NDJ 2018-2019 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL SEASONAL MEAN  
TEMPERATURES FOR MUCH OF THE FORECAST DOMAIN TO INCLUDE ALL OF ALASKA AND MOST  
OF THE WESTERN AND NORTHERN CONTIGUOUS U.S. THE GREATEST PROBABILITIES FOR  
ABOVE-NORMAL TEMPERATURES ARE INDICATED FOR WESTERN AND NORTHERN ALASKA AND TO  
A LESSER DEGREE THE PACIFIC NORTHWEST. FOR SEASONAL TOTAL PRECIPITATION AMOUNTS  
DURING NDJ 2018-2019, THERE ARE MODESTLY ELEVATED CHANCES OF ABOVE-NORMAL  
PRECIPITATION FOR MOST OF THE SOUTHERN TIER OF THE CONTIGUOUS U.S., THE CENTRAL  
EASTERN SEABOARD, AND SOUTHERN ALASKA.  
 
EQUAL CHANCES (EC) FOR ABOVE-, NEAR-, OR BELOW-NORMAL SEASONAL MEAN  
TEMPERATURES OR SEASONAL TOTAL PRECIPITATION AMOUNTS ARE INDICATED IN AREAS  
WHERE THE LIKELIHOOD OF THESE VARIABLES ARE FAVORED TO BE SIMILAR TO  
CLIMATOLOGICAL PROBABILITIES. THE REASONS FOR THIS CAN BE A COMBINATION OF  
WEAKLY DEFINED OR NON-RELIABLE CLIMATE FACTORS AS WELL AS CONSIDERABLE SPREAD  
IN FORECAST TOOL SOLUTIONS.  
 
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  
 
STARTING WITH OCEAN CONDITIONS, WE CONTINUE TO REMAIN IN ENSO-NEUTRAL  
CONDITIONS THROUGH EARLY OCTOBER AND THE EL NINO WATCH CONTINUES. IN RECENT  
WEEKS, HOWEVER, OBSERVATIONS ACROSS THE GLOBAL TROPICS HAVE TRENDED TOWARD MORE  
FAVORABLE CONDITIONS FOR DEVELOPMENT OF EL NINO IN THE NEXT COUPLE OF MONTHS.  
SEA SURFACE TEMPERATURES (SSTS) ARE ABOVE-NORMAL ACROSS MOST OF THE EQUATORIAL  
PACIFIC BASIN, GENERALLY RANGING FROM +0.5 - +1.0 DEGREES C. THE MOST RECENT  
WEEKLY VALUES OF THE NINO4 AND NINO3.4 INDICES ARE NOW +0.9 AND +0.6 DEGREES C  
RESPECTIVELY. THIS SOMEWHAT RAPID CHANGE WAS CONSIDERABLY AIDED BY THE  
DEVELOPMENT OF A WESTERLY WIND BURST (WWB) AND EVOLUTION OF AN ONGOING MJO  
EVENT AND THE ASSOCIATED WESTERLY LOW-LEVEL WIND ANOMALIES. A STRONG  
DOWNWELLING OCEANIC KELVIN WAVE WAS INITIATED AS A RESULT OF THIS SIGNIFICANT  
WEAKENING OF THE PACIFIC BASIN TRADE WINDS DUE TO THESE EVENTS AND CONTINUES TO  
SHIFT EASTWARD ACROSS THE PACIFIC BASIN AT DEPTH. ACCORDINGLY, THE EQUATORIAL  
UPPER-OCEAN HEAT CONTENT HAS INCREASED CONSIDERABLY DURING SEPTEMBER AND EARLY  
OCTOBER MAKING THE DEVELOPMENT OF EL NINO SOMEWHAT MORE LIKELY. SPECIFIC  
NINO3.4 SST FORECASTS ARE REVIEWED IN THE SECTION BELOW.  
 
THE ATMOSPHERIC CONDITIONS ASSOCIATED WITH A DEVELOPING EL NINO EVENT REMAIN  
MODEST AT BEST. ALTHOUGH WESTERLY LOW-LEVEL WIND ANOMALIES ARE NOW PRESENT, ANY  
ORGANIZED AREAS OF ENHANCED CONVECTION ARE NOT YET PRESENT. THIS IS MOST  
LIKELY, HOWEVER, IN PART DUE TO THE COUNTER-ACTING EFFECT FROM LARGE SCALE  
SUBSIDENCE ASSOCIATED WITH THE SUPPRESSED CONVECTIVE PHASE OF THE MJO.  
 
TURNING TO CURRENT TERRESTRIAL CONDITIONS, WE NOTE MUCH ABOVE-NORMAL SOIL  
MOISTURE ANOMALIES FROM TEXAS TO THE MIDWEST, EASTWARD TO THE GREAT LAKES,  
MID-ATLANTIC AND PARTS OF THE NORTHEAST, WHILE DROUGHT CONDITIONS PERSIST  
ACROSS MANY AREAS OF THE WEST. AS WE ARE ENTERING THE LATE AUTUMN AND WINTER  
MONTHS, SOIL MOISTURE CONDITIONS, ALTHOUGH NEAR THE 99TH PERCENTILE IN MANY  
AREAS, IS NOT EXPECTED TO CONTRIBUTE ANY SIGNIFICANT IMPACT TO THE CLIMATE  
CONDITIONS OVER THE NEXT SEVERAL MONTHS. SNOW COVER ANOMALIES (BOTH NEGATIVE  
AND POSITIVE) FOR SEPTEMBER AND THE FIRST HALF OF OCTOBER ARE IMPORTANT TO  
NOTE. SNOWFALL OVER AREAS OF EURASIA AND ALASKA ARE CURRENTLY BELOW-NORMAL IN  
MANY AREAS, BUT SNOWFALL HAS BEEN SUBSTANTIALLY ABOVE-NORMAL FOR PORTIONS OF  
CENTRAL AND EASTERN CANADA.  
 
PROGNOSTIC DISCUSSION OF SST FORECASTS  
 
FORECASTS OF THE NINO3.4 SST ANOMALY HAVE NOT CHANGED VERY MUCH OVER THE PAST  
FEW MONTHS TO FIRST ORDER. THE CPC CONSOLIDATION NINO3.4 SST ANOMALY FORECAST  
MAINTAINS ITS RECENT PREDICTIONS OVER THE PAST SEVERAL MONTHS WITH A PEAK IN  
POSITIVE ANOMALY DURING NDJ 2018-2019 OF JUST UNDER +1.0 DEGREE C AND THEN  
SLOWLY DECREASES OVER THE COURSE OF THE WINTER AND SPRING MONTHS OF 2019,  
ALTHOUGH THE FORECAST IS TEMPERED BY AN OUTLIER FORECAST FROM THE CCA  
STATISTICAL MODEL. THIS MODEL FORECAST REMAINS IN ENSO-NEUTRAL TERRITORY  
THROUGH THE WINTER AND INCREASES THEREAFTER. THE NMME NINO3.4 SST ANOMALY MODEL  
GUIDANCE ALSO HAS REMAINED CONSISTENT OVER THE PAST FEW MONTHS AND CONTINUES TO  
INDICATE A SLIGHTLY STRONGER EVENT (ENSEMBLE MEAN PEAKING AND PERSISTING  
BETWEEN +1.0 - +1.2 DEGREES C) DURING THE WINTER AND SPRING MONTHS. THE  
OFFICIAL CPC-IRI ENSO OUTLOOK FAVORS EL NINO THIS WINTER AND SPRING AT A  
GREATER THAN 70% PROBABILITY THROUGH JFM 2019 AND THEN DECREASING TO NEAR 50%  
BY AMJ 2019.  
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS  
 
THIS SET OF OUTLOOKS UTILIZED TYPICAL IMPACTS ASSOCIATED WITH EL NINO EVENTS,  
ALBEIT WITH THE UNDERSTANDING THAT THIS MOST LIKELY WILL BE A WEAK EVENT AND  
NOTING THE CONFIDENCE IN THIS IMPACTS IN INTENSITY AND LOCATION IS SOMEWHAT  
LOW. MOREOVER, IT IS NOTED THAT DUE TO ITS LIKELY WEAK NATURE, THE VARIANCE  
EXPLAINED IN THE MID-LATITUDES OVER THE EARLY PORTION OF THIS SET OF OUTLOOKS  
FROM THE TROPICAL PACIFIC COULD VERY WELL BE LOW. OTHER FACTORS FROM BOTH THE  
TROPICS (E.G., MJO) AND HIGH/POLAR LATITUDES (E.G., AO/NAO, NPO, ETC.) ARE  
LIKELY TO FAVOR HIGH VARIABILITY OVER THE WINTER AND EARLY SPRING SEASONS AND  
LIKELY WILL EXPLAIN CONSIDERABLY MORE VARIANCE IN THE UPCOMING SEASONAL MEANS  
IN TEMPERATURE AND PRECIPITATION.  
 
LOCAL COASTAL SSTS AND CONSIDERATIONS OF AREAS OF ANOMALOUS SNOWFALL WERE  
CONSIDERED IN MAKING THE OUTLOOKS.  
 
CONTRIBUTIONS TO THE OUTLOOKS ALSO INCLUDED BIAS-CORRECTED AND CALIBRATED  
DYNAMICAL MODEL GUIDANCE FROM THE NMME AND IMME ENSEMBLE SUITES (BOTH ENSEMBLE  
MEAN AND THEIR PARTICIPANT MODELS) THROUGH MAM 2019. EMPIRICAL AND STATISTICAL  
FORECAST MODELS ALSO PLAYED A LARGE ROLE THROUGHOUT ALL FORECAST LEADS. THESE  
INCLUDED GUIDANCE FROM A COMBINED ENSO-OCN TOOL, THE CCA, THE CA, AND  
"BRIDGING" TECHNIQUES. MOREOVER, CONSOLIDATION FORECAST GUIDANCE PRODUCTS FROM  
STATISTICAL ONLY, DYNAMICAL MODEL ONLY, AND COMBINED STATISTICAL AND DYNAMICAL  
FORECAST TOOLS WAS HEAVILY UTILIZED. OCN ALSO WAS UTILIZED OFTEN THROUGHOUT THE  
OUTLOOK LEADS FOR BOTH TEMPERATURE AND PRECIPITATION.  
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - NDJ 2018 TO NDJ 2019  
 
TEMPERATURE  
 
IN REVIEWING THE FIRST FOUR FORECAST LEADS THROUGH THE WINTER 2018-2019 AND  
EARLY SPRING MONTHS IN 2019, THE NDJ AND DJF 2018-2019 TEMPERATURE OUTLOOKS ARE  
SIMILAR AND DEPICT ELEVATED ODDS OF ABOVE-NORMAL TEMPERATURES FOR ALASKA AND  
MUCH OF THE WESTERN AND NORTHERN CONUS WITH EC NOTED FOR THE SOUTHEAST. AS WE  
PROGRESS THROUGH THE WINTER INTO THE EARLY SPRING, THE FORECAST SEQUENCE  
DEPICTS A TENDENCY FOR THE ODDS OF ABOVE-NORMAL TEMPERATURES TO DECREASE ALONG  
WITH FORECAST COVERAGE FIRST FOR THE OHIO VALLEY AND MID-ATLANTIC AND THEN  
LATER IN THE GREAT LAKES AND NORTHEAST BY FMA 2019 WHERE EC IS FORECAST. IN  
ADDITION, OVER THE SAME TIME, THERE IS AN EASTERN EXPANSION OF ENHANCED ODDS  
FOR ABOVE-NORMAL TEMPERATURES ACROSS THE SOUTHERN PLAINS INTO THE SOUTHEAST  
CONUS. FOR THESE LEADS, OTHER THAN AREAS IN ALASKA AND THE PACIFIC NORTHWEST,  
THE PROBABILITIES ARE QUITE MODEST.  
 
THIS DEPICTED EVOLUTION (VARIATION OF AREAS DENOTED AS EC) IN THE FORECAST OF  
SEASONAL MEAN TEMPERATURES IS A RESULT OF CHANGING AREAS WITH THE GREATEST  
UNCERTAINTY AND SO LOWER FORECAST CONFIDENCE. UNDERSTANDING THE WEAK NATURE OF  
EL NINO ANTICIPATED THIS WINTER AND CONFRONTED BY CONSIDERABLE CONFLICTING  
FORECAST TOOL INFORMATION IN THESE AREAS, EC IS FORECAST AT THIS TIME. DURING  
NDJ AND DJF 2018-2019, DYNAMICAL MODEL GUIDANCE FROM THE NMME DEPICTS  
CALIBRATED PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES NEARLY UNANIMOUSLY  
ACROSS MUCH OF THE NORTH IN AGREEMENT WITH THE AFOREMENTIONED STATISTICAL  
FORECAST TOOLS AND OBJECTIVE, SKILL WEIGHTED CONSOLIDATION GUIDANCE PRODUCTS.  
 
AS WE PROGRESS THROUGH THE WINTER, POSITIVE TEMPERATURE TRENDS IN MANY AREAS NO  
LONGER EXIST AND CALIBRATED DYNAMICAL MODEL GUIDANCE PROBABILITIES DECREASE  
SUBSTANTIALLY, ALONG WITH LITTLE HISTORICAL FORECAST SKILL INDICATED. AN  
ADDITIONAL FACTOR IS THAT THE ECMWF SEASONAL PREDICTION FAVORS BELOW-NORMAL  
TEMPERATURES FOR A CONSIDERABLE AREA THAT STRETCHES FROM THE SOUTHERN PLAINS  
AND PARTS OF THE SOUTHEAST CONUS IN NDJ 2018-2019 TO AN EXPANDED AREA THAT  
INCLUDES THE CENTRAL PLAINS, CENTRAL MISSISSIPPI VALLEY, OHIO VALLEY, AND  
MID-ATLANTIC. MOREOVER, THE ENSO-OCN TOOL AND OBJECTIVE, SKILL WEIGHTED  
CONSOLIDATION FORECAST TOOLS INDICATE A VARYING MIXTURE OF QUITE MODEST  
PROBABILITIES FOR EITHER OF THE THREE FORECAST CATEGORIES.  
 
IN ADDITION, UNCERTAINTIES IN THE PREDOMINATE PHASE OF THE AO/NAO AND MJO  
ACTIVITY ESPECIALLY FROM MID-WINTER INTO EARLY SPRING MAKE A FORECAST OF EC NOT  
AN UNREASONABLE CHOICE AS VARIABILITY OVERALL IS LIKELY TO BE HIGH AND DEPEND  
ON CONSIDERABLE IMPACTS ASSOCIATED WITH BOTH TROPICAL AND HIGH LATITUDE  
SUBSEASONAL VARIABILITY WHICH IS DIFFICULT TO PREDICT AT THESE FORECAST LEADS.  
 
FOR ALASKA AND THE WESTERN CONUS, THERE IS LITTLE SUPPORT FOR ANY OTHER  
FORECAST BESIDES ELEVATED ODDS FOR ABOVE-NORMAL TEMPERATURES FOR THIS PORTION  
OF THE SET OF OUTLOOKS AS WELL AS THE REMAINING OUTLOOKS THROUGH NDJ 2019-2020.  
THE PRIMARY DRIVER FOR THE OUTLOOKS FROM MJJ 2019 THROUGH NDJ 2019-2020 WERE  
OCN, ENSO-OCN, AND STATISTICAL OBJECTIVE, SKILL WEIGHTED CONSOLIDATION  
FORECAST TOOLS.  
 
PRECIPITATION  
 
THE OUTLOOKS FOR SEASONAL TOTAL PRECIPITATION AMOUNTS UTILIZED INFORMATION  
CONSISTENT WITH AN ANTICIPATED (ALBEIT WEAK) EL NINO EVENT FROM NDJ 2018-2019  
THROUGH MAM 2019. DYNAMICAL MODEL GUIDANCE FROM THE NMME AND IMME CONTRIBUTED  
TO THE OUTLOOKS AS WELL THROUGH MAM 2019. GIVEN THE RANGE OF SOLUTIONS AND  
GENERALLY WEAK INDICATORS FROM MANY OF THE FORECAST TOOLS, PROBABILITIES FOR  
EITHER FORECAST CATEGORY (ABOVE- OR BELOW-NORMAL PRECIPITATION) ARE QUITE  
MODEST, NOT REACHING 50% PROBABILITY FROM THE CLIMATOLOGICAL PROBABILITY OF 33%  
UNTIL DJF 2018-2019 AND JFM 2019 WHEN A SMALL AREA FAVORING ABOVE-NORMAL  
PRECIPITATION IS INDICATED FOR AN AREA IN SOUTHERN GEORGIA AND NORTHERN  
FLORIDA. THIS AREA IS A PART OF A LARGER REGION OF FAVORED ABOVE-NORMAL  
PRECIPITATION ACROSS THE SOUTHERN TIER OF THE CONUS THROUGH MAM 2019. PRIMARILY  
SUPPORTED BY DYNAMICAL MODEL GUIDANCE, AN INCREASE IN COVERAGE OF THIS REGION  
IN THE CENTRAL ROCKIES AND CENTRAL PLAINS DURING JFM AND FMA 2019 IS FORECAST.  
 
BELOW-NORMAL PRECIPITATION IS FAVORED FOR PARTS OF PACIFIC NORTHWEST AND  
NORTHERN ROCKIES IN NDJ 2018-2019 AND THEN PRIMARILY CENTERED ACROSS MONTANA  
DURING JFM AND FMA 2019. SIMILARLY, BELOW NORMAL PRECIPITATION IS FAVORED FOR  
PARTS OF THE GREAT LAKES AND LATER THE OHIO VALLEY OVER THE SEASONS FROM DJF  
2018-2019 TO FMA 2019. EL NINO CONSIDERATIONS AND CONSISTENT DYNAMICAL MODEL  
GUIDANCE FAVORED ELEVATED ODDS OF ABOVE-NORMAL PRECIPITATION FOR SOUTHERN  
ALASKA THROUGH FMA 2019. THERE WAS CONSIDERABLE CONFLICTING FORECAST TOOL  
INFORMATION (SEVERAL SOURCES) FOR THE EARLY LEADS ACROSS CALIFORNIA SO EC WAS  
INDICATED AT THIS TIME FOR THIS REGION EXCEPT FOR A SMALL AREA IN SOUTHERN  
CALIFORNIA.  
 
FROM AMJ 2019 THROUGH NDJ 2019-2020, THE OUTLOOKS ARE BASED PREDOMINATELY ON  
LONG TERM TRENDS AS DIAGNOSED BY OCN FOR EACH FORECAST SEASON. TO THIS END, THE  
MOST BROAD AND CONSISTENT SIGNALS FOR THIS ARE ELEVATED ODDS FOR BELOW-NORMAL  
PRECIPITATION IN THE NORTHERN ROCKIES FROM MJJ 2019 THROUGH JAS 2019 AND A  
LARGER AREA FOR FAVORED ABOVE-NORMAL PRECIPITATION FOR PARTS OF THE GREAT  
LAKES, NORTHEAST, OHIO VALLEY, AND MID-ATLANTIC FROM MJJ 2019 THROUGH OND 2019.  
 
FORECASTER: JON GOTTSCHALCK  
 
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 NOV 15 2018  
 
1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011  
FORECAST RELEASE.  

 
 
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