813  
FXUS05 KWBC 151330  
PMD90D  
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
830 AM EST THU FEB 15 2018  
 
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS  
 
LA NINA CONDITIONS CONTINUED THROUGH JANUARY AND INTO EARLY FEBRUARY ACROSS THE  
EQUATORIAL PACIFIC OCEAN, AS INDICATED BY OCEANIC AND ATMOSPHERIC OBSERVATIONS.  
THE CPC/IRI CONSENSUS ENSO FORECAST INDICATES THAT LA NINA CONDITIONS ARE  
EXPECTED TO DECAY RAPIDLY AND TRANSITION TO ENSO-NEUTRAL CONDITIONS DURING THE  
NORTHERN HEMISPHERE SPRING. ENSO-NEUTRAL CONDITIONS ARE FAVORED TO PERSIST  
THROUGH AT LEAST THE BOREAL SUMMER.  
 
THE MARCH-APRIL-MAY (MAM) 2018 TEMPERATURE OUTLOOK INDICATES ABOVE-NORMAL  
TEMPERATURES ARE MOST LIKELY ACROSS THE SOUTHERN TIER OF THE CONUS, WITH  
GREATER THAN 60 PERCENT PROBABILITY ACROSS MUCH OF THE SOUTHWEST AND SOUTHERN  
PLAINS WITH GREATER THAN 70 PERCENT PROBABILITY IN SOME AREAS OF NEW MEXICO AND  
TEXAS. LESS ELEVATED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES EXTEND UP THE  
EAST COAST INTO THE NORTHEAST. ABOVE-NORMAL TEMPERATURES ARE ALSO MOST LIKELY  
FOR WESTERN COASTAL AREAS OF ALASKA, INCLUDING THE ALEUTIAN ISLANDS, AS WELL AS  
THE NORTH SLOPE, WITH SEA ICE SEASONALLY LOW IN THE BERING SEA AND DECREASED  
SNOW LEVELS IN SOUTHWEST ALASKA. INCREASED PROBABILITIES OF BELOW NORMAL  
TEMPERATURES ARE FORECAST FOR SOUTHEASTERN MAINLAND ALASKA AND THE ALASKA  
PANHANDLE, WHERE SNOW LEVELS ARE MOSTLY ABOVE AVERAGE. INCREASED PROBABILITIES  
FOR BELOW-NORMAL TEMPERATURES DURING MAM ARE FORECAST FOR PARTS OF THE PACIFIC  
NORTHWEST, THE NORTHERN ROCKIES, AND THE NORTHERN HIGH PLAINS.  
 
THE MAM 2018 PRECIPITATION OUTLOOK INDICATES ELEVATED PROBABILITIES OF  
ABOVE-NORMAL PRECIPITATION FOR THE NORTHERN ROCKIES, EAST ACROSS THE NORTHERN  
GREAT PLAINS INTO THE MIDWEST, THE OHIO VALLEY AND THE NORTHEAST, AND SOUTH TO  
THE TENNESSEE VALLEY. INCREASED PROBABILITIES OF ABOVE-NORMAL PRECIPITATION ARE  
ALSO INDICATED FOR NORTHWESTERN ALASKA. BELOW-NORMAL PRECIPITATION IS MOST  
LIKELY FROM CALIFORNIA ACROSS THE GREAT BASIN AND SOUTHWEST INTO THE CENTRAL  
AND SOUTHERN GREAT PLAINS, AS WELL AS ALONG THE GULF COAST INTO FLORIDA.  
BELOW-NORMAL PRECIPITATION IS ALSO MOST LIKELY FOR THE SOUTHERN COAST OF  
ALASKA, INCLUDING THE ALEUTIAN ISLANDS AND THE ALASKA PANHANDLE.  
 
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  
 
OCEANIC OBSERVATIONS INDICATE THAT LA NINA CONDITIONS CONTINUED THROUGH JANUARY  
INTO EARLY FEBRUARY, AS CENTRAL AND EASTERN EQUATORIAL SST ANOMALIES ARE  
NEGATIVE FROM THE DATE LINE TO THE SOUTH AMERICAN COAST. THE LATEST WEEKLY NINO  
3.4 TEMPERATURE ANOMALY WAS -0.9 C. NEGATIVE SUB-SURFACE TEMPERATURE ANOMALIES  
IN THE CENTRAL AND EAST-CENTRAL EQUATORIAL PACIFIC WEAKENED IN EARLY JANUARY  
AND STRENGTHENED AGAIN IN LATE JANUARY AND EARLY FEBRUARY, WITH ANOMALOUSLY  
WARM WATER AT DEPTHS OF GREATER THAN 200 METERS IN THE WESTERN PACIFIC. THE  
MOST RECENT THREE MONTH MEAN TEMPERATURE ANOMALY FOR THE NINO 3.4 REGION, FOR  
NOVEMBER 2017 THROUGH JANUARY 2018, IS -1.0 C.  
 
RECENT ATMOSPHERIC CONDITIONS OVER THE TROPICAL PACIFIC OCEAN ARE ALSO  
CONSISTENT WITH LA NINA, WITH SUPPRESSED CONVECTION NEAR THE INTERNATIONAL DATE  
LINE AND ENHANCED CONVECTION OVER THE MARITIME CONTINENT. UPPER-LEVEL WINDS AT  
200-HPA ARE ANOMALOUSLY WESTERLY OVER THE CENTRAL AND EASTERN PACIFIC.  
 
THE MADDEN JULIAN OSCILLATION (MJO) IS ACTIVE WITH ENHANCED CONVECTION OVER THE  
WESTERN PACIFIC. DYNAMICAL MODELS FORECAST THE ACTIVE PHASE OF THE MJO TO  
PROPAGATE EASTWARD AND WEAKEN IN THE NEXT COUPLE WEEKS. THE ACTIVE MJO IS  
EXPECTED TO HAVE AN IMPACT ON TEMPERATURES FOR NORTH AMERICA IN MARCH. THE  
IMPACT OF MJO ON THE FORECAST DECREASES IN APRIL AND MAY WITH GREATER  
UNCERTAINTY.  
 
PROGNOSTIC DISCUSSION OF SST FORECASTS  
 
THE CPC SST-CONSOLIDATION FORECAST, WHICH INCLUDES THE CONSTRUCTED ANALOG,  
MARKOV, AND CANONICAL CORRELATION ANALYSIS STATISTICAL FORECASTS, ALONG WITH  
THE CFS DYNAMICAL MODEL FORECAST, PREDICTS A TRANSITION FROM LA NINA TO  
ENSO-NEUTRAL CONDITIONS IS LIKELY DURING SPRING 2018 WITH ENSO-NEUTRAL  
CONDITIONS MOST LIKELY FOR MAM 2018 AND SEASONS THAT FOLLOW. MOST ENSEMBLE  
MEMBERS OF THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) PREDICT THE NINO 3.4  
SST ANOMALY TO BE BETWEEN -0.5 AND 0.5 C, INDICATING LIKELY ENSO-NEUTRAL  
CONDITIONS, BY APRIL 2018. THE NMME-MEAN NINO 3.4 TEMPERATURE ANOMALY IS  
BETWEEN 0.0 C AND 0.5 C FROM JUNE THROUGH SEPTEMBER 2018. BASED ON THE LATEST  
OBSERVATIONS AND MODEL FORECASTS, THE OFFICIAL CPC/IRI ENSO CONSENSUS INDICATES  
THAT ENSO-NEUTRAL CONDITIONS ARE MOST LIKELY FOR THE MAM 2018 SEASON AND  
THEREAFTER, WITH PROBABILITIES EXCEEDING 50 PERCENT THROUGH JJA 2018.  
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS  
 
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR MAM 2018 THROUGH JJA 2018 WERE  
PRIMARILY BASED ON DYNAMICAL MODEL GUIDANCE, INCLUDING THE NCEP CLIMATE  
FORECAST SYSTEM (CFS) AND THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME), AS  
WELL AS STATISTICAL GUIDANCE, INCLUDING A MODEL COMBINING REGRESSIONS OF  
TEMPERATURE/PRECIPITATION ON THE CPC SST-CONSOLIDATION OF NINO3.4 FORECASTS  
WITH DECADAL TRENDS. GUIDANCE FOR FMA 2018 THROUGH JAS 2018 WAS ALSO OBTAINED  
FROM A STATISTICAL-DYNAMICAL HYBRID MODEL THAT MERGES A STATISTICAL FORECAST OF  
TEMPERATURE/PRECIPITATION PROBABILITIES FROM NMME FORECASTS OF THE NINO 3.4 SST  
ANOMALY WITH CALIBRATED NMME TEMPERATURE/PRECIPITATION PROBABILITY FORECASTS.  
THE LONGER-LEAD OUTLOOKS, FROM ASO 2018 THROUGH MAM 2019, WERE BASED ON DECADAL  
TEMPERATURE/PRECIPITATION TRENDS, AS WELL AS THE CPC TEMPERATURE/PRECIPITATION  
CONSOLIDATION OF STATISTICAL FORECASTS.  
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2018 TO MAM 2019  
 
TEMPERATURE  
 
ABOVE-NORMAL TEMPERATURES DURING MAM 2018 ARE MOST LIKELY ACROSS MUCH OF THE  
SOUTHERN HALF OF THE U.S., NORTHWARD UP THE ATLANTIC COAST TO MAINE, AS WELL AS  
WESTERN AND NORTHERN ALASKA. PROBABILITIES ARE GREATEST FOR THE SOUTHWEST AND  
SOUTHERN PLAINS, AS WELL AS FOR WESTERN AND NORTHERN REGIONS OF ALASKA, WHERE  
POSITIVE DECADAL TEMPERATURE TRENDS ARE LARGEST. BELOW-NORMAL TEMPERATURES ARE  
MORE LIKELY FOR PARTS OF THE PACIFIC NORTHWEST AND NORTHERN HIGH PLAINS, AS  
WELL AS SOUTHEASTERN MAINLAND ALASKA AND THE ALASKA PANHANDLE. THIS TEMPERATURE  
PATTERN IS CONSISTENT WITH IMPACTS OF CURRENT LA NINA CONDITIONS. AN ACTIVE MJO  
INCREASES THE PROBABILITIES OF BELOW-NORMAL TEMPERATURES OVER MUCH OF THE  
NORTHERN AND CENTRAL GREAT PLAINS IN MARCH, AND INCREASES THE UNCERTAINTY OF  
THE MARCH TEMPERATURE OUTLOOK OVER A LARGE PART OF THE EAST, AS INCREASED  
PROBABILITIES OF BELOW-NORMAL TEMPERATURES FROM MJO IMPACTS CONFLICT WITH  
INCREASED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES IN THE SEASONAL OUTLOOK.  
AS A RESULT, PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ARE MODERATED OVER THE  
EAST IN THE MAM 2018 OUTLOOK.  
 
THE AREA OF LIKELY ABOVE-NORMAL TEMPERATURES INCREASES THROUGH THE SON 2018  
OUTLOOK, FOLLOWING CALIBRATED TEMPERATURE FORECASTS FROM THE NMME, LARGELY DUE  
TO DECADAL TRENDS AND A DIMINISHED ROLE OF ENSO IMPACTS. PROBABILITIES OF  
ABOVE-NORMAL TEMPERATURES HAVE INCREASED IN THE FEBRUARY SEASONAL OUTLOOKS  
THROUGH SON 2018, RELATIVE TO THE JANUARY SEASONAL OUTLOOKS, FOLLOWING GUIDANCE  
FROM THE CALIBRATED NMME FORECASTS AND FROM STATISTICAL ANALYSIS OF THE DECADAL  
TRENDS. ABOVE-NORMAL TEMPERATURES ARE NOW MOST LIKELY OVER A GREATER AREA OF  
THE CENTRAL AND UPPER MISSISSIPPI VALLEY FOR JJA THROUGH ASO 2018. THE SEASONAL  
OUTLOOKS FOR OND 2018 THROUGH MAM 2018 FOLLOW GUIDANCE FROM THE CPC  
CONSOLIDATION, INDICATING AREAS OF LIKELY ABOVE-NORMAL TEMPERATURES, LARGELY  
DUE TO DECADAL TRENDS.  
 
PRECIPITATION  
 
THE MAM AND AMJ 2018 PRECIPITATION OUTLOOKS INDICATE BELOW-NORMAL PRECIPITATION  
IS MOST LIKELY FOR A LARGE PART OF THE SOUTHERN CONUS, INCLUDING CALIFORNIA,  
THE GREAT BASIN, THE SOUTHWEST, AND THE GULF COAST. ABOVE-NORMAL PRECIPITATION  
IS MOST LIKELY FROM THE NORTHERN ROCKIES ACROSS PARTS OF THE NORTHERN PLAINS  
INTO THE MIDWEST, INCLUDING THE CENTRAL AND UPPER MISSISSIPPI VALLEY, AS WELL  
AS THE OHIO VALLEY AND THE TENNESSEE VALLEY. THIS PRECIPITATION PATTERN IS  
CONSISTENT WITH THE PERSISTENT IMPACTS OF LA NINA. INCREASED PROBABILITIES OF  
ABOVE-NORMAL PRECIPITATION FOR THE NORTHEAST ARE SUPPORTED BY FORECASTS FROM  
THE NMME AND CFS DYNAMICAL MODELS, AS WELL AS STATISTICAL GUIDANCE BASED ON  
DECADAL TRENDS. INCREASED PROBABILITIES OF BELOW-NORMAL PRECIPITATION MOVE INTO  
PARTS OF THE NORTHWEST CONUS FROM MJJ THROUGH JAS 2018, FOLLOWING CALIBRATED  
NMME FORECASTS AND DECADAL TRENDS.  
 
NMME FORECASTS OF INCREASING LIKELIHOOD AS THE SUMMER PROGRESSES OF EL NINO  
CONDITIONS AND RELATED IMPACTS ARE PARTLY DISCOUNTED, DUE TO LOW SKILL IN BOTH  
THE ENSO AND PRECIPITATION FORECASTS AT THIS TIME OF YEAR. A SLIGHT INCREASE IN  
THE PROBABILITIES OF BELOW-NORMAL PRECIPITATION IS INDICATED FOR PARTS OF THE  
CENTRAL PLAINS FROM MJJ THROUGH JAS 2018, SUPPORTED BY CALIBRATED NMME FORECAST  
PROBABILITIES AND HYBRID STATISTICAL-DYNAMICAL NMME FORECASTS. THE GREATER AREA  
OVER THE CENTRAL CONUS OF INCREASED PROBABILITIES OF BELOW-NORMAL PRECIPITATION  
IN THE CALIBRATED NMME PROBABILITIES IS NOT SUPPORTED BY EITHER ENSO IMPACTS OR  
DECADAL PRECIPITATION TRENDS. INCREASED PROBABILITIES OF ABOVE-NORMAL  
PRECIPITATION FOR THE NORTHEAST THROUGH ASO 2018 ARE SUPPORTED BY DECADAL  
PRECIPITATION TRENDS. THE PROBABILITIES OF BELOW-NORMAL PRECIPITATION ARE  
INCREASED FOR THE SOUTHERN COAST OF ALASKA FROM MAM THROUGH AMJ 2018, WHILE  
ABOVE-NORMAL PRECIPITATION IS MOST LIKELY FOR NORTHWESTERN ALASKA FROM MAM 2018  
THROUGH JJA 2018, AS INDICATED BY CALIBRATED PROBABILITY FORECASTS FROM THE  
NMME, CONSISTENT WITH DECADAL TRENDS.  
 
WITH NO CLEAR CLIMATE SIGNALS OR PRECIPITATION TRENDS, OUTLOOKS FOR SON 2018  
THROUGH MAM 2019 INDICATE EQUAL CHANCES (EC), WHERE PROBABILITIES OF  
PRECIPITATION ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES.  
 
FORECASTER: DAN COLLINS  
 
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 MAR 15 2018  
 
1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011  
FORECAST RELEASE.  

 
 
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