90 Day Narrative

052 
FXUS05 KWBC 201230
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU JUL 20 2017
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS
THE AUGUST-SEPTEMBER-OCTOBER (ASO) 2017 TEMPERATURE OUTLOOK INDICATES INCREASED 
CHANCES OF ABOVE-NORMAL TEMPERATURES ACROSS ALASKA AND THE CONTIGUOUS U.S., 
ALTHOUGH PROBABILITIES ARE REDUCED FROM PARTS OF THE SOUTHERN PLAINS TO THE 
CENTRAL MISSISSIPPI VALLEY. THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL 
TEMPERATURES ARE FORECAST FOR PARTS OF THE NORTHERN ROCKIES AND INTERMOUNTAIN 
WEST, THE GULF COAST AND ATLANTIC COASTS, THE NORTHEAST, AND WESTERN AREAS OF 
ALASKA. THE ASO 2017 PRECIPITATION OUTLOOK INDICATES AN INCREASED CHANCE FOR 
ABOVE-MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHERN PLAINS, THE SOUTHWEST, 
SOUTHWESTERN ALASKA, AND THE ALEUTIAN ISLANDS.
DURING THE AUTUMN AND WINTER 2017-18, THE CHANCES OF EL NINO DEVELOPMENT ARE 
LOWER COMPARED TO LAST MONTH. SINCE ENSO-NEUTRAL CONDITIONS ARE MOST LIKELY TO 
PERSIST, THE TEMPERATURE AND PRECIPITATION OUTLOOKS DURING THE COLD SEASON ARE 
BASED PRIMARILY ON DYNAMICAL MODEL GUIDANCE AND DECADAL TRENDS.
EQUAL CHANCES (EC) ARE FORECAST OVER AREAS WHERE PROBABILITIES OF ABOVE-, 
BELOW-, OR NEAR-NORMAL SEASONAL MEAN TEMPERATURES AND 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. WHILE SEA SURFACE TEMPERATURES (SSTS) ARE SLIGHTLY 
ABOVE AVERAGE IN THE EAST-CENTRAL PACIFIC OCEAN, ATMOSPHERIC CONDITIONS ARE 
REPRESENTATIVE OF ENSO-NEUTRAL CONDITIONS. THE OBSERVED WEEKLY SSTS CENTERED ON 
JULY 12 INDICATE POSITIVE SST ANOMALIES OF 0.5 TO 1 DEGREE C JUST TO THE WEST 
OF THE DATE LINE AND FROM ABOUT 170W TO 120W LONGITUDE ALONG THE EQUATOR. THE 
UPPER-OCEAN TEMPERATURE ANOMALY IS ABOVE AVERAGE ACROSS MUCH OF THE EQUATORIAL 
PACIFIC OCEAN TO A DEPTH OF 100 TO 150 METERS, THOUGH WITH WEAK ANOMALIES OF 
LESS THAN 2 DEGREES C.
DESPITE WARMER-THAN-AVERAGE OCEAN TEMPERATURES ACROSS THE CENTRAL AND EASTERN 
PACIFIC SINCE MARCH, ATMOSPHERIC CONVECTIVE ANOMALIES FROM JUNE 17 TO JULY 12 
CONTINUE TO REMAIN NEAR AVERAGE FROM NEAR THE DATE LINE TO THE EASTERN TROPICAL 
PACIFIC. ENHANCED CONVECTION WAS OBSERVED ACROSS PARTS OF INDONESIA DURING THIS 
TIME PERIOD. WESTERLY ANOMALIES IN LOWER LEVEL WINDS AT 850-HPA WERE OBSERVED 
OVER THE EAST-CENTRAL TROPICAL PACIFIC, WHILE EASTERLY ANOMALIES WERE OBSERVED 
IN UPPER LEVEL 200-HPA WINDS OVER THE EASTERN PACIFIC. THESE ATMOSPHERIC 
INDICATORS ARE CONSISTENT WITH ENSO-NEUTRAL CONDITIONS.
PROGNOSTIC DISCUSSION OF SST FORECASTS
MOST MODELS OF THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) INDICATE A 
CONTINUATION OF ENSO-NEUTRAL CONDITIONS THROUGH THE AUTUMN, WITH SOME MODELS 
INDICATING WEAK TO MODERATE EL NINO CONDITIONS. THE NCEP CFSV2 PREDICTS 
NEAR-ZERO TEMPERATURE ANOMALIES IN THE EAST-CENTRAL TROPICAL PACIFIC OCEAN BY 
THE BEGINNING OF AUTUMN. THE CPC NINO 3.4 SST CONSOLIDATION OF THE CFS AND 
STATISTICAL FORECASTS INDICATES ELEVATED PROBABILITIES OF POSITIVE TEMPERATURE 
ANOMALIES THROUGH SON, AND A TEMPERATURE ANOMALY CLOSE TO ZERO DEGREES IS MOST 
LIKELY BY OND. THE CPC/IRI CONSENSUS FORECAST INDICATES PERSISTENCE OF 
ENSO-NEUTRAL CONDITIONS IS MOST LIKELY THROUGH FMA 2018 WITH A PROBABILITY 
GREATER THAN 50%, WHILE THE PROBABILITY OF DEVELOPMENT OF EL NINO CONDITIONS 
REMAINS ELEVATED FROM CLIMATOLOGICAL PROBABILITIES AND IS AT OR ABOVE 35% 
THROUGH OND. 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
DYNAMICAL MODELS PROVIDE THE PRIMARY GUIDANCE FOR THE SEASONAL OUTLOOKS THROUGH 
DJF 2017-2018, WITH DECADAL TEMPERATURE AND PRECIPITATION TRENDS PROVIDING THE 
PRIMARY GUIDANCE FOR LONGER LEADS. THE CALIBRATED PROBABILITY FORECASTS FROM 
THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) AND ANOMALY FORECASTS FROM ITS 
INDIVIDUAL MODELS, INCLUDING THE NCEP CFS, WERE USED THROUGH DJF 2017/2018. THE 
DECREASING LIKELIHOOD OF EL NINO DEVELOPMENT, COMPARED TO PREVIOUS OUTLOOKS LED 
TO ADJUSTMENTS IN THE OUTLOOKS, ESPECIALLY FOR THE WINTER SEASONS. 
PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2017 TO ASO 2018
TEMPERATURE
ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS ALL OF THE FORECAST DOMAIN FOR THE 
ASO OUTLOOK, AS WELL AS OUTLOOKS FOR SON 2017 THROUGH NDJ 2017-2018, AS 
INDICATED BY A CONSENSUS OF MODELS FROM THE NMME, DRIVEN SOMEWHAT BY DECADAL 
TEMPERATURE TRENDS. LOWER PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE 
INDICATED FOR ASO AND SON FROM PARTS OF TEXAS AND THE SOUTHERN PLAINS TO THE 
CENTRAL MISSISSIPPI VALLEY, DUE TO POTENTIAL MODERATION OF TEMPERATURES BY 
INCREASED SOIL MOISTURE IN RESPONSE TO PREDICTED PRECIPITATION IN THIS REGION. 
THE HIGHEST PROBABILITIES OF ABOVE NORMAL TEMPERATURES IN ASO ARE INDICATED FOR 
PARTS OF THE NORTHERN ROCKIES AND INTERMOUNTAIN WEST, AS WELL AS ALONG THE GULF 
AND ATLANTIC COASTS, AND THE NORTHEAST, WHERE DECADAL TRENDS ARE GREATER IN 
COMPARISON TO SEASONAL VARIABILITY. PROBABILITIES IN THE SOUTHWEST, WHERE 
DECADAL TRENDS ARE ALSO LARGE, ARE MODERATED BY A FORECAST FOR ABOVE MEDIAN 
PRECIPITATION AND RESULTING SURFACE-ATMOSPHERIC FEEDBACKS. PROBABILITIES FOR 
ABOVE-NORMAL TEMPERATURES ARE ALSO HIGHEST FOR PARTS OF SOUTHWESTERN, WESTERN 
AND NORTHWESTERN ALASKA, AS INDICATED BY THE PROBABILITY FORECASTS OF THE NMME, 
LARGELY RESULTING FROM DECADAL TRENDS. 
 
WITH ENSO-NEUTRAL CONDITIONS MOST LIKELY THROUGH WINTER, THE TEMPERATURE 
OUTLOOKS FROM ASO 2017 TO DJF 2017-18 ARE BASED PRIMARILY ON THE NMME 
CALIBRATED PROBABILITY FORECASTS. AN EXPECTED LACK OF SEA ICE ELEVATES CHANCES 
FOR ABOVE-NORMAL TEMPERATURES ACROSS NORTHERN ALASKA DURING THE AUTUMN. DECADAL 
TRENDS ARE USED AS GUIDANCE FOR THE TEMPERATURE OUTLOOKS AT LONGER LEADS FROM 
MAM TO ASO 2018 AND INDICATE INCREASED PROBABILITIES OF ABOVE-NORMAL 
TEMPERATURES WHERE TRENDS ARE THE LARGEST RELATIVE TO SEASONAL TEMPERATURE 
VARIABILITY. 
PRECIPITATION
ENHANCED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION FOR THE NORTHERN PLAINS 
DURING THE FIRST SEVERAL LEADS IN LAST MONTHS OUTLOOKS HAVE BEEN REMOVED FROM 
THE CURRENT OUTLOOKS, WHERE EQUAL CHANCES IS NOW INDICATED. THIS CHANGE IS 
BASED ON THE MOST RECENT DYNAMICAL MODEL GUIDANCE FROM THE NMME AND CFS. 
CALIBRATED PRECIPITATION PROBABILITY FORECASTS FROM THE NMME INDICATE ABOVE 
MEDIAN PRECIPITATION IS MOST LIKELY FOR PARTS OF TEXAS AND THE SOUTHERN PLAINS 
EXTENDING EASTWARD TO THE MISSISSIPPI RIVER. THIS SIGNAL CONTINUES IN THE 
OUTLOOKS FOR SON 2017 THROUGH DJF 2017-2018. A CONSENSUS OF THE DYNAMICAL 
MODELS INDICATE AN INCREASED CHANCE OF BELOW MEDIAN PRECIPITATION FOR PARTS OF 
PACIFIC NORTHWEST FOR ASO. THE AUGUST PRECIPITATION FORECASTS FROM THE MOST 
RECENT RUNS OF THE CFS AND ADDITIONAL DYNAMICAL MODEL FORECASTS FOR THE 
BEGINNING OF AUGUST CONSISTENTLY INDICATE ABOVE MEDIAN PRECIPITATION FOR AUGUST 
IN THE SOUTHWEST MONSOON REGION. AS THE MONTH OF AUGUST HAS GREATER 
PRECIPITATION IN THIS REGION THAN THE FOLLOWING MONTHS, ENHANCED PRECIPITATION 
IN AUGUST HAS AN INCREASED IMPACT ON THE TOTAL SEASONAL PRECIPITATION. ABOVE 
MEDIAN PRECIPITATION IS THEREFORE INDICATED FOR THE SOUTHWEST FOR ASO. ABOVE 
MEDIAN PRECIPITATION IS INDICATED FOR PARTS OF SOUTHERN ALASKA IN ASO 2017 
THROUGH DJF 2017-2018, AS INDICATED BY CALIBRATED PRECIPITATION PROBABILITY 
FORECASTS FROM THE NMME. DUE TO DECADAL TRENDS, ABOVE MEDIAN PRECIPITATION IS 
MOST LIKELY FOR PARTS OF THE NORTHERN PLAINS AND GREAT LAKES REGION FROM MAM TO 
MJJ 2018, AND FOR PARTS OF THE NORTHEAST FROM MJJ THROUGH ASO 2018. 
SINCE THE PREVIOUS OUTLOOK, THE CHANCES FOR EL NINO DEVELOPMENT DURING THE 
AUTUMN AND WINTER HAVE DECREASED. GIVEN THE LATEST ENSO FORECAST INDICATING A 
GREATER CHANCE OF ENSO-NEUTRAL CONDITIONS THROUGH THE WINTER, THE INCREASED 
CHANCES FOR BELOW MEDIAN PRECIPITATION FOR PARTS OF THE NORTHERN ROCKIES IN NDJ 
AND DJF 2017-2018 HAVE BEEN REMOVED. PRECIPITATION OUTLOOKS FROM JFM THROUGH 
FMA 2018 ARE BASED ON THE SEASONAL PRECIPITATION CONSOLIDATION FORECAST AND 
DECADAL TRENDS. 
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 AUG 17 2017
1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 
FORECAST RELEASE.
$$