032  
FXUS07 KWBC 311900  
PMD30D  
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT TUE JUL 31 2018  
 
30-DAY OUTLOOK DISCUSSION FOR AUGUST 2018  
 
THE UPDATED MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS FOR AUGUST 2018 ARE  
BASED ON THE LATEST MODEL GUIDANCE AND RECENT SHORT AND EXTENDED RANGE OUTLOOKS  
FROM NCEP CENTERS.  
 
THE UPDATED TEMPERATURE OUTLOOK FOR AUGUST IS SIMILAR OVERALL TO THE AUGUST  
TEMPERATURE OUTLOOK RELEASED ON JULY 19, WITH SOME CHANGES. ABOVE NORMAL  
AVERAGE TEMPERATURES FOR AUGUST ARE INCREASINGLY LIKELY FOR THE WESTERN CONUS,  
WITH DYNAMICAL MODEL FORECASTS FOR MOST AREAS OF THE WEST AT THE BEGINNING OF  
THE MONTH INDICATING POSITIVE ANOMALIES, AS WELL AS GUIDANCE FROM THE NCEP CFS  
FOR THE FULL MONTH. BELOW NORMAL TEMPERATURES ARE MOST LIKELY FOR PARTS OF THE  
PACIFIC NORTHWEST EARLY IN THE MONTH. HOWEVER, BY THE END OF THE MONTH, ABOVE  
NORMAL TEMPERATURES ARE MORE LIKELY FOR THE ENTIRE WEST. DYNAMICAL MODEL  
FORECASTS, INCLUDING THE CFS, INDICATE AN INCREASED POTENTIAL FOR BELOW NORMAL  
TEMPERATURES OVER THE NORTHERN CENTRAL AND SOUTHEASTERN CONUS DURING THE FIRST  
HALF OF WEEK 1. GUIDANCE FOR THE AVERAGE TEMPERATURES FOR THE WEEK 3 AND 4  
PERIOD, INCLUDING THE CFS, ECMWF, AND SUBSEASONAL EXPERIMENT (SUBX) ENSEMBLES,  
INDICATE BELOW NORMAL TEMPERATURES MAY RETURN LATE IN THE MONTH. HOWEVER  
GUIDANCE FOR THE WEEK 2 PERIOD, DECADAL TRENDS, AND SEASONAL CLIMATE SIGNALS  
INDICATE LOW PROBABILITIES THAT AVERAGE AUGUST TEMPERATURES WILL BE BELOW  
NORMAL. EQUAL CHANCES OF ABOVE, NEAR AND BELOW NORMAL TEMPERATURES IS INDICATED  
FOR A LARGE AREA OF THE NORTHERN AND CENTRAL PLAINS, THE UPPER AND CENTRAL  
MISSISSIPPI VALLEY, THE OHIO VALLEY, AND PARTS OF THE SOUTHEAST TO THE ATLANTIC  
COAST. ABOVE NORMAL TEMPERATURES CONTINUE TO BE LIKELY FOR THE NORTHEAST, AS  
INDICATED BY FORECAST GUIDANCE FOR WEEKS 1 THROUGH 4. ABOVE NORMAL TEMPERATURES  
ARE LIKELY FOR MUCH OF THE SOUTHERN PLAINS, FOLLOWING FORECAST GUIDANCE FOR  
WEEK 2 FROM THE GEFS AND ECMWF ENSEMBLES, AND FOR WEEKS 2 THROUGH 4 FROM  
VARIOUS MEMBER MODELS OF SUBX. INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES  
ARE INDICATED FOR ALL REGIONS OF ALASKA, WHERE MODEL FORECASTS INDICATE BELOW  
NORMAL TEMPERATURES DURING WEEK 2 AND ABOVE NORMAL TEMPERATURES AT THE  
BEGINNING AND END OF THE MONTH.  
 
THE UPDATED PRECIPITATION OUTLOOK FOR AUGUST IS SIMILAR OVERALL TO THE AUGUST  
PRECIPITATION OUTLOOK RELEASED ON JULY 19, BUT INDICATES SIGNIFICANT CHANGES IN  
THE OUTLOOK FOR THE EASTERN CONUS, AS WELL AS SMALLER CHANGES IN OTHER REGIONS.  
FORECAST GUIDANCE FOR WEEKS 1 THROUGH 4 INDICATE AN INCREASED PROBABILITY OF  
ABOVE NORMAL PRECIPITATION OVER MUCH OF THE EASTERN CONUS, FROM THE EASTERN  
GREAT LAKES REGION, SOUTHWARD INTO THE OHIO VALLEY AND MID-ATLANTIC REGION, TO  
THE SOUTHEAST AND EASTERN GULF COAST STATES. WPC FORECASTS INDICATE A GREATER  
PROBABILITY OF PRECIPITATION THAN PREVIOUSLY ACROSS PARTS OF THE CENTRAL PLAINS  
DURING THE END OF WEEK 1. HOWEVER, MODEL GUIDANCE, INCLUDING THE CFS AND SUBX  
ENSEMBLE MODELS, FOR THE FIRST HALF OF THE MONTH INDICATES BELOW NORMAL  
PRECIPITATION IS LIKELY FOR MUCH OF THE CENTRAL AND SOUTHERN PLAINS. DYNAMICAL  
MODEL FORECASTS AND THE CPC EXPERIMENTAL PRECIPITATION OUTLOOK FOR WEEKS 3 AND  
4 INDICATE ABOVE NORMAL PRECIPITATION IS MORE LIKELY THAN BELOW NORMAL FOR  
PARTS OF THE CENTRAL PLAINS, INCLUDING SOUTHERN NEBRASKA, KANSAS, AND NORTHERN  
OKLAHOMA, LATE IN THE MONTH. THE UPDATED MONTHLY OUTLOOK INDICATES BELOW NORMAL  
PRECIPITATION FOR AUGUST REMAINS LIKELY FOR A SMALLER AREA OF THE SOUTHERN  
PLAINS, EXTENDING NORTHWARD INTO CENTRAL OKLAHOMA. ABOVE NORMAL PRECIPITATION  
CONTINUES TO BE LIKELY FOR MUCH OF THE SOUTHWEST, FROM SOUTHERN CALIFORNIA INTO  
PARTS OF THE THE FOUR CORNERS STATES, SUPPORTED BY THE LATEST MODEL GUIDANCE  
FROM THE CFS, AS WELL AS OTHER ENSEMBLE PREDICTION SYSTEMS. ABOVE NORMAL  
PRECIPITATION CONTINUES TO BE LIKELY FOR WESTERN ALASKA, SUPPORTED BY DYNAMICAL  
MODEL FORECASTS, INCLUDING THE CFS.  
 
THE PREVIOUS DISCUSSION FROM THE HALF-MONTH LEAD MONTHLY FORECAST FOLLOWS.  
 
_____________________________________________________________________________  
 
THE AUGUST 2018 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL  
MODEL GUIDANCE, STATISTICAL FORECASTS, CURRENT SOIL MOISTURE CONDITIONS, AND  
POTENTIAL INFLUENCES FROM MODES OF TROPICAL VARIABILITY. THE STATE OF ENSO DOES  
NOT IMPACT THE FORECAST, AS ENSO-NEUTRAL CONDITIONS ARE EXPECTED THROUGH MOST  
OF SUMMER, WHILE AN EL NINO WATCH HAS BEEN ISSUED INDICATING THAT EL NINO  
CONDITIONS ARE LIKELY THEREAFTER. THE MADDEN-JULIAN OSCILLATION (MJO) IS ACTIVE  
WITH CONVECTION LOCATED OVER THE MARITIME CONTINENT AND PREDICTED BY SOME  
MODELS TO POSSIBLY MOVE INTO THE WESTERN PACIFIC IN THE NEXT WEEK. BECAUSE  
THERE IS SIGNIFICANT UNCERTAINTY IN THE MJO DYNAMICAL MODEL FORECASTS, AND MJO  
IMPACTS ON NORTH AMERICAN TEMPERATURE AND PRECIPITATION PATTERNS IS LIMITED AT  
THIS TIME OF YEAR, MJO DID NOT PLAY A ROLE IN THE AUGUST OUTLOOKS.  
 
MODEL FORECASTS FROM THE NMME, MORE RECENT RUNS FROM THE CFS, AND TRENDS FAVOR  
ABOVE NORMAL TEMPERATURES ACROSS THE WESTERN CONUS, AS WELL AS THE NORTHEAST.  
ABOVE NORMAL TEMPERATURES ARE MOST LIKELY FOR WESTERN AND SOUTHERN PARTS OF  
ALASKA, WITH ABOVE AVERAGE SEA SURFACE TEMPERATURES (SSTS) PRESENT IN THE GULF  
OF ALASKA AND BERING SEA, AND PREDICTED TO PERSIST BY DYNAMICAL MODEL FORECASTS  
FROM THE NMME. UNCERTAINTY IS GREATER FOR NORTHEASTERN ALASKA AND THE ARCTIC  
COAST, WHERE SSTS HAVE BEEN BELOW NORMAL AND MODELS SHOW GREATER UNCERTAINTY.  
RECENT RUNS OF THE CFS CONSISTENTLY PREDICT ABOVE NORMAL TEMPERATURES ARE  
LIKELY FOR THE SOUTHERN PLAINS, AS WELL AS WESTERN AREAS OF THE CENTRAL AND  
LOWER MISSISSIPPI VALLEY, AS FAR NORTH AS MISSOURI. CONTINUING DRY SOIL  
MOISTURE CONDITIONS ALSO SUPPORT ENHANCED CHANCES OF ABOVE NORMAL TEMPERATURES  
FOR AUGUST IN THIS REGION. PROBABILITIES OF ABOVE NORMAL TEMPERATURES EXCEED 50  
PERCENT FOR SOUTHERN AREAS OF TEXAS, LOUISIANA AND FLORIDA, INFLUENCED BY ABOVE  
AVERAGE SSTS FOR THE GULF OF MEXICO. DYNAMICAL MODEL FORECASTS FOR THE  
BEGINNING OF AUGUST, INCLUDING THE CFS AND THE ECMWF ENSEMBLE PREDICTION  
SYSTEM, AS WELL AS RECENT FORECASTS FROM THE SUBSEASONAL EXPERIMENT (SUBX)  
MODELS, INDICATE LIKELY BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN  
PLAINS INTO WESTERN AREAS OF THE MIDWEST, WHILE CALIBRATED PROBABILITY  
FORECASTS FROM THE NMME INDICATE WEAK PROBABILITIES OF ABOVE NORMAL  
TEMPERATURES OR EQUAL CHANCES OF ABOVE AND BELOW NORMAL. AN AREA OF EQUAL  
CHANCES IS INDICATED IN THE NORTH-CENTRAL CONUS, WHERE THERE IS GREATER  
UNCERTAINTY IN THE MEAN AUGUST TEMPERATURES. WEAK PROBABILITIES FOR ABOVE  
NORMAL TEMPERATURES ARE INDICATED FOR MUCH OF THE EASTERN CONUS, WHERE SKILL IS  
LOWER, AND FORECASTS INDICATE BELOW NORMAL TEMPERATURES AT THE BEGINNING OF  
AUGUST. PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR THE SOUTHWEST MONSOON  
REGION ARE LOWER, WHERE ENHANCED PRECIPITATION MAY MODERATE TEMPERATURES.  
 
MODEL FORECASTS FROM THE NMME AND RECENT RUNS OF THE CFS INDICATE ABOVE NORMAL  
PRECIPITATION IS LIKELY FOR MUCH OF THE WESTERN CONUS, INCLUDING THE SOUTHWEST  
MONSOON REGION, EXTENDING NORTHWARD INTO SOUTHERN AREAS OF IDAHO AND WYOMING.  
ENHANCED PROBABILITIES OF ABOVE NORMAL PRECIPITATION EXTEND INTO SOUTHERN  
CALIFORNIA, AS CONVECTIVE ACTIVITY OVER THE EAST PACIFIC MAY LEAD TO MOISTURE  
SURGES INTO THIS REGION. IF THE MJO REMAINS ACTIVE AND ENHANCED CONVECTION DUE  
TO MJO PROGRESSES EASTWARD, MOISTURE TRANSPORT INTO THE WEST COAST MAY BE  
FURTHER INCREASED. ABOVE NORMAL PRECIPITATION IS LIKELY FOR WESTERN ALASKA, AS  
INDICATED BY THE NMME AND CFS FORECASTS. PROBABILITIES OF ABOVE NORMAL  
PRECIPITATION ARE ALSO SLIGHTLY ENHANCED FOR PARTS OF THE ATLANTIC COAST FROM  
NORTHERN FLORIDA TO VIRGINIA, SUPPORTED BY NMME MODEL FORECASTS FOR THE  
ATLANTIC COAST. PROBABILITIES OF BELOW NORMAL PRECIPITATION ARE ENHANCED FOR  
COASTAL AREAS OF THE PACIFIC NORTHWEST, AS INDICATED BY RECENT DYNAMICAL MODEL  
GUIDANCE. THE CHANCES OF BELOW NORMAL PRECIPITATION ARE SLIGHTLY ENHANCED FROM  
PARTS OF THE SOUTHERN PLAINS INTO THE WESTERN MISSISSIPPI VALLEY FROM LOUISIANA  
TO MISSOURI, SUPPORTED BY ONGOING DRY SOIL MOISTURE CONDITIONS, AS WELL AS SOME  
MODELS OF THE NMME, INCLUDING THE CFS. IT SHOULD BE NOTED THAT PRECIPITATION  
FORECASTS FOR THE CONUS IN SUMMER HAVE LOW SKILL, THEREFORE PROBABILITIES ARE  
WEAK OVER MOST OF THE FORECAST DOMAIN.  
 
FORECASTER: DAN COLLINS  
 
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.  
 
THE NEXT MONTHLY OUTLOOK...FOR SEP ... WILL BE ISSUED ON THU AUG 16 2018  
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.  

 
 
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