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.
$$