117  
FXUS07 KWBC 201410  
PMD30D  
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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