PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
830 AM EDT THU JUL 20 2017 
 
30-DAY OUTLOOK DISCUSSION FOR AUGUST 2017 
 
THE AUGUST 2017 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL 
MODEL GUIDANCE, STATISTICAL TOOLS, CURRENT SOIL MOISTURE CONDITIONS, AND 
POTENTIAL INFLUENCES FROM MODES OF TROPICAL VARIABILITY. ENSO IS NOT A FACTOR 
IN THESE OUTLOOKS SINCE IT IS IN A NEUTRAL STATE AND IS PREDICTED TO REMAIN 
NEUTRAL. PLEASE SEE THE ENSO DIAGNOSTIC DISCUSSION AT: 
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/ANALYSIS_MONITORING/ENSO_ADVISORY/ENSODISC 
.SHTML FOR A MORE DETAILED ANALYSIS OF SEA SURFACE TEMPERATURES ACROSS THE 
EQUATORIAL PACIFIC. THE MADDEN-JULIAN OSCILLATION (MJO) BECAME MORE COHERENT 
DURING MID-JULY WITH ITS ENHANCED PHASE OVER THE WESTERN MARITIME CONTINENT. A 
COHERENT MJO SIGNAL IS FAVORED TO PROPAGATE EASTWARD DURING THE NEXT TWO WEEKS, 
BUT ITS EFFECTS ON THE EXTRATROPICS ARE EXPECTED TO BE MINIMAL GIVEN THE TIME 
OF YEAR. THE CFS MODEL INDICATES AN ATMOSPHERIC KELVIN WAVE (KW) CROSSING THE 
WESTERN HEMISPHERE DURING LATE JULY INTO THE BEGINNING OF AUGUST. THIS KW COULD 
PROVIDE A FAVORABLE ENVIRONMENT FOR TROPICAL CYCLONE DEVELOPMENT OVER THE EAST 
PACIFIC AND CONTRIBUTE TO A CONTINUATION OF ENHANCED MOISTURE ACROSS THE 
SOUTHWESTERN U.S. 
 
THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) DEPICTS INCREASED PROBABILITIES 
FOR ABOVE-NORMAL TEMPERATURES ACROSS NEARLY ALL OF THE CONTINENTAL U.S. THE 
LARGEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES IN THE OFFICIAL OUTLOOK ARE 
FORECAST ACROSS THE NORTHERN GREAT PLAINS WHERE CURRENT SOIL MOISTURE VALUES 
RANK BELOW THE 10TH PERCENTILE.  ALSO, THE GFS, ECMWF, AND CANADIAN ENSEMBLE 
MEANS INDICATE THAT THE ANOMALOUS 500-HPA RIDGE IS LIKELY TO PERSIST AT LEAST 
THROUGH THE BEGINNING OF AUGUST. ALTHOUGH MANY OF THE DYNAMICAL MODELS FAVOR 
ABOVE-NORMAL TEMPERATURES ACROSS THE SOUTHWESTERN U.S., EQUAL CHANCES FOR 
BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ARE FORECAST FOR THIS REGION BASED 
ON A CONSISTENT SIGNAL AMONG DAILY RUNS OF THE NCEP CLIMATE FORECAST SYSTEM 
(CFS) MODEL, DEPICTING NEAR TO BELOW-NORMAL TEMPERATURES, AND THE ENHANCED ODDS 
FOR ABOVE-MEDIAN PRECIPITATION FORECAST IN THE PRECIPITATION OUTLOOK. 
 
THE PROBABILITY ANOMALY CORRELATION (PAC) CALIBRATED PROBABILITY FORECAST FROM 
THE NMME FEATURES LITTLE IF ANY SIGNAL THROUGHOUT MOST OF THE FORECAST DOMAIN 
WITH ONLY A SLIGHT TILT IN THE ODDS (36 TO 40 PERCENT) FOR THE ABOVE NORMAL 
TERCILE FROM THE RIO GRANDE VALLEY NORTH TO THE CENTRAL ROCKIES. THE MOST 
CONSISTENT SIGNAL AMONG DAILY CFS MODEL RUNS IS A FAVORED AREA OF ABOVE-MEDIAN 
PRECIPITATION OVER THE RIO GRANDE VALLEY AND PARTS OF THE WESTERN U.S. BASED ON 
THESE TWO PRECIPITATION TOOLS ALONG WITH POTENTIAL INFLUENCES FROM AN EXPECTED 
ACTIVE PERIOD OF EAST PACIFIC TROPICAL CYCLONE ACTIVITY, ABOVE-MEDIAN 
PRECIPITATION IS FAVORED FOR THE RIO GRANDE VALLEY, MOST OF THE MONSOON REGION 
OF THE SOUTHWESTERN U.S., AND THE CENTRAL ROCKIES. FORECAST CONFIDENCE IN THE 
PRECIPITATION OUTLOOK IS LIMITED DUE TO THE LACK OF PREDICTABILITY OF 
CONVECTIVE RAINFALL ON A MONTHLY TIME SCALE. 
 
THE DYNAMICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH INCREASED CHANCES OF 
ABOVE-NORMAL TEMPERATURES ACROSS ALASKA. THE HIGHEST PROBABILITIES FOR 
ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS THE ALASKA PENINSULA ALONG WITH 
PARTS OF WESTERN AND SOUTHERN ALASKA, BASED IN PART ON SEA SURFACE TEMPERATURES 
AVERAGING 1 TO 3 DEGREES C ABOVE NORMAL. THE DYNAMICAL MODEL CONSENSUS FAVORS A 
RELATIVELY WET AUGUST ACROSS WESTERN ALASKA. 
 
 
FORECASTER: BRAD PUGH 
 
 
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING 
THE WORLD METEOROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 
COMPLETE DECADES AS THE CLIMATE 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. 
 
 
 
AN UPDATED MONTHLY OUTLOOK... FOR AUG WILL BE ISSUED ON MON JULY 31 2017 
 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. 
 
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