Prognostic Meteorological Discussion
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000 FXUS10 KWNH 311838 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 238 PM EDT FRI JUL 31 2015 VALID JUL 31/1200 UTC THRU AUG 04/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... FINAL 12Z MODEL EVALUATION AND PREFERENCES UPPER HIGH EXTENDING FROM OREGON INTO TEXAS... SHORTWAVE TROUGH INFLUENCING THE GREAT BASIN/N. ROCKIES THIS WEEKEND... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND GFS/ECMWF CONFIDENCE: AVERAGE MODELS SHOW STRONG AGREEMENT IN MAINTAINING THE HIGH OVER TEXAS THROUGH THE WEEKEND WITH ITS ASSOCIATED SHORTWAVE RIDGE EXTENDING INTO OREGON...BUT BEGINNING TO ERODE ALONG ITS WESTERN EDGES BY LATE SATURDAY. BY LATE SATURDAY INTO EARLY SUNDAY...MODELS REMAIN CONSISTENT MOVING SHORTWAVE ENERGY ACROSS THE GREAT BASIN AND EVENTUALLY INTO THE NORTHERN ROCKIES. WHILE THESE SOLUTIONS INVOLVE THE INTERACTIONS OF NUMEROUS SHORT WAVELENGTH ELEMENTS INCLUDING THE INFLUENCE OF CONVECTION THAT MAY RESULT IN DIFFERENT OUTCOMES IN FUTURE CYCLES...THE GENERAL MODEL EVOLUTION APPEARS REASONABLE. REGARDING MODEL CHOICES...THE 12Z GFS AND 0Z ECMWF REMAIN THE MOST CONSISTENT AND CLOSEST TO THE ENSEMBLE MEANS. THE 0Z UKMET AND 0Z CMC ARE TRENDING CLOSER TO THE ECMWF/GFS AS WELL. THE 12Z NAM BREAKS DOWN THE UPPER RIDGE QUICKER AND APPEARS TO BE AN OUTLIER WITH THIS SOLUTION. THUS AT THIS TIME A BLEND OF THE 12Z GFS AND 0Z ECMWF REMAINS THE PREFERRED SOLUTION. FINAL PREFERENCE UPDATE: THE 12Z ECMWF/CMC/UKMET ALL CAME IN WITH SIMILAR SOLUTIONS TO THE PREVIOUS PREFERENCE. THUS WILL CONTINUE TO SUGGEST AN ECMWF/GFS BLEND WITH GROWING CONFIDENCE. UPPER TROUGH EXTENDING FROM THE GREAT LAKES SOUTHWARD... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF BLEND CONFIDENCE: AVERAGE MODELS IN GOOD AGREEMENT WITH THE GENERAL IDEA OF A TROUGH BUILDING INTO THE EAST. HOWEVER THEY DIFFER WITH THE EXACT TIMING OF INDIVIDUAL SHORTWAVES MOVING ACROSS THE GREAT LAKES. IN GENERAL THE TREND AMONG THE GUIDANCE HAS BEEN TO INJECT SLIGHTLY MORE ENERGY INTO THE TROUGH...RESULTING IN A SLIGHTLY QUICKER AND DEEPER SOLUTION. THE LATEST 12Z NAM/GFS CONTINUE TO TREND IN THIS DIRECTION...WITH THE 0Z ECMWF ON THE SLOWER SIDE AND MORE IN LINE WITH THE 0Z CMC. THE 0Z UKMET APPEARS TO OFFER A LESS PROBABLE SOLUTION...BEING MUCH WEAKER THAN THE REMAINDER OF THE GUIDANCE. GIVEN RECENT TRENDS WOULD HEDGE A BIT TOWARDS THE QUICKER 12Z NAM/GFS SOLUTIONS...ALTHOUGH LIKELY NOT AS DEEP AS THE NAM. ENSEMBLE MEANS ARE SLOWER THAN THE DETERMINISTIC RUNS...BUT THE MEANS CAN BE LATE TO CATCH ON TO TRENDS AT TIMES. GIVEN THIS...WOULD NOT COMPLETELY RULE OUT A SLOWER SOLUTION CLOSER TO THE ECMWF...AND THUS THE WPC PREFERENCE WILL REMAIN A BLEND OF THE ECMWF/GFS THOUGH HEDGED TOWARDS THE GFS. FINAL PREFERENCE UPDATE: THE 12Z ECMWF/UKMET/CMC DID IN GENERAL TREND TOWARDS THE NAM/GFS WITH REGARDS TO TIMING. HOWEVER THEY REMAIN ON THE WEAKER SIDE. THUS AT THIS TIME THE 12Z NAM SEEMS TO OFFER A LESS PROBABLE SOLUTION GIVEN ITS SHORTWAVE STRENGTH AND DEEPER TROUGH. THUS AN EVEN BLEND OF THE 12Z GFS/ECMWF STILL SEEMS LIKE A GOOD PREFERENCE REPRESENTING A MIDDLE GROUND SOLUTION. CLOSED LOW NEARING THE PACIFIC NORTHWEST SUNDAY NIGHT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF BLEND CONFIDENCE: AVERAGE THE 0Z UKMET AND 12Z GFS ARE NOW ON THE QUICKER SIDE OF THE GUIDANCE WITH THIS FEATURE...THE 12Z NAM AND 0Z ECMWF IN BETWEEN...AND THE 0Z CMC ON THE SLOWER SIDE. THE TREND AMONG THE DETERMINISTIC GUIDANCE HAS DEFINITELY BEEN FOR A QUICKER SOLUTION. THIS WOULD SEEM TO SUGGEST THE CMC IS AN UNLIKELY SOLUTION. THE 12Z GFS AND 0Z UKMET ARE QUICKER THAN THEIR ENSEMBLE MEANS...BUT STILL REPRESENT A POSSIBLE SOLUTION. THUS FOR NOW THE WPC PREFERENCE IS BETWEEN THE 12Z GFS AND 0Z ECMWF...AGAIN HEDGED TOWARDS THE 12Z GFS GIVEN TRENDS. FINAL PREFERENCE UPDATE: THE 12Z ECMWF/CMC DID BOTH TREND QUICKER WITH THIS UPPER LOW AND THE 12Z UKMET A BIT SLOWER. THIS IN GENERAL DECREASED THE SPREAD AMONG THE GUIDANCE...WITH THE 12Z GFS NOW BEING A FAST OUTLIER. HOWEVER GIVEN RECENT TRENDS FOR A QUICKER SOLUTION...IT CAN NOT BE COMPLETELY RULED OUT. THUS A BLEND OF THE 12Z GFS/ECMWF STILL SEEMS TO OFFER THE BEST CONSENSUS POSITION AT THIS TIME. ...MODEL TREND GRAPHICS AT www.wpc.ncep.noaa.gov/html/model2.shtml... ...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD $$

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