PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU JUL 19 2018


30-DAY OUTLOOK DISCUSSION FOR AUGUST 2018

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.

AN UPDATED MONTHLY OUTLOOK... FOR AUG WILL BE ISSUED ON TUE JULY 31 2018

THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.
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