MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1208 PM EDT TUE AUG 16 2016 VALID AUG 16/1200 UTC THRU AUG 20/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHORTWAVE CROSSING WESTERN GREAT LAKES INTO SE CANADA/N MAINE THROUGH WED EVENING WITH WEAKENING TRAILING KICKER WAVE AND LINGERING TROF ACROSS OH/MS RIVER VALLEYS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS ARE FAIRLY WELL AGREED UPON WITH RESPECT TO THE 7H/SFC REFLECTION CROSSING LK HURON AND MOVING ACROSS N ME/NB THROUGH WED WITH THE LINGERING CONFLUENCE/FRONTAL ZONE ACROSS THE OH/MID TO LOWER MS RIVER VALLEYS. A WEAK KICKER WAVE CROSSES THE GREAT LAKES AS WELL THROUGH THURS EVENTUALLY SHEARING INTO THE DIGGING TROF OUT OF QUEBEC (SEE SECTION BELOW)... THE 12Z NAM IS THE ONLY MODEL TO BREAK FROM MODERATE CONSENSUS FOLLOWING TRADITIONAL BIAS OF BEING A BIT DEEPER/AMPLIFIED ACROSS UPPER OH RIVER VALLEY INTO THE MID-ATLANTIC THURS/FRI. ADDITIONALLY...THE NAM HAS SOME FEEDBACK ISSUED RESOLVING A MORE WOUND UP SOLUTION ALONG THE SOUTHWESTERN PORTION OF THE TROF ACROSS TX/LOWER MS VALLEY THURS/FRIDAY. AS SUCH WILL PREFER A NON-NAM BLEND (MAINLY FOR THE SECOND/KICKER WAVE) AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. AMPLIFYING TROF CROSSING SE QUEBEC CLIPPING MAINE/SE CANADA THUR/FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: AVERAGE A WEAKLY CLOSED WAVE CROSSING FROM MANITOBA INTO S HUDSON BAY WILL CONTINUE TO TRACK E THEN SE CROSSING QUEBEC WITH SURFACE REFLECTION ACROSS THE ST. LAWRENCE SEAWAY CLIPPING N MAINE THURSDAY EVENING INTO FRIDAY. THE 12Z NAM HAS TRENDED A BIT FASTER MOVING INTO LINE WITH THE ECMWF/GFS AND UKMET AND A BULK OF ENSEMBLE SOLUTIONS; THOUGH THERE REMAINS SOME MODERATE SPREAD TO THOSE FASTER SOLUTIONS. THIS LEAVES THE 00Z CMC LAGGING THE OVERALL COMPOSITE ENOUGH SO TO SUPPORT A NON-CMC BLEND FOR THIS SYSTEM THOUGH WITH THE SPREAD...CONFIDENCE IS AVERAGE IN THE REMAINING BLENDED SOLUTIONS. CLOSED LOW IN CANADA AND DEVELOPING TROF ACROSS ACROSS ROCKIES/N PLAINS BY FRIDAY INCLUDING ENERGY FROM CENTRAL ROCKIES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/NAM AND 00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE NUMEROUS MOVING PARTS ACROSS ROCKIES AND WESTERN CANADA THAT WILL EVENTUALLY EVOLVE INTO A BROADER/AMPLIFYING WESTERN TROF THROUGH THE END OF THE WEEK. THE LEAD AND MOST WELL AGREED UPON FEATURE IS THE SHORTWAVE AMPLIFYING ACROSS N BC/ALBERTA THAT WILL CLOSE OFF ACROSS N CENTRAL CANADA AND SUPPORT HEIGHT FALLS ACROSS THE SOUTHERN PRAIRIES AFFECTING FLOW IN THE NORTHERN PLAINS. AN INCREASINGLY LARGE MODEL SPREAD EXISTS BY FRIDAY (MAINLY OVER THE U.S.) DRIVEN BY THE OTHER FEATURES WITHIN THE DEVELOPING TROF. THE OVERALL GLOBAL WAVE PATTERN WITH ENERGETIC PACIFIC TROF, STATIC RIDGE OVER COASTAL BC/NORTHEAST PACIFIC OCEAN AND THIS DIGGING TROF ACROSS THE ROCKIES WILL CONTAIN HIGH VARIATION GIVEN THE TIMING/PLACEMENT OF THE PACIFIC ENERGY SHEARING/OVER-TOPPING THE RIDGE INTO THE WESTERN PORTION OF THE TROF AS EVIDENCE BY THE VARIATION IN THE RUN TO RUN ENSEMBLE SPREAD. AN ADDITIONAL IMPORTANT PLAYER IS A SHORTWAVE OVER THE FOUR CORNERS REGION THAT WILL LIFT NORTHEAST AND EJECT INTO THE NORTHERN PLAINS SUPPORTING A WEAK SURFACE TROF WED BEFORE STRONGER HEIGHT FALLS ENCOURAGE A STRONGER SURFACE REFLECTION ACROSS THE BLACK HILLS THURSDAY BEFORE THE FRONTAL ZONE EXTENDS FROM THE CANADIAN LOW ACROSS THE WESTERN GREAT LAKES INTO THE CENTRAL PLAINS BY FRIDAY. AS IT IS ALOFT, THE PLACEMENT/TIMING IS AGREED UPON BUT THE MAGNITUDE AND EXACT PLACEMENT OF THE SURFACE WAVES REMAIN HIGHLY SPREAD. THE 00Z ECMWF SHOWS A STRONGER/SLOWER WOUND UP SOLUTION THAT ALSO DELAYS THE NORTHWARD LIFT OF THE 4-CORNERS S/W PERHAPS TOO MUCH...TYPICAL OF ITS BIAS WHILE THE 00Z ECENS MEAN SEEMS TO TEMPER THIS BIAS TOWARD SOMETHING MORE IN LINE WITH CURRENT THINKING. THIS IS FURTHER SUPPORTED BY A SLOWING OF BOTH THE 12Z NAM/GFS. THE 12Z NAM HOWEVER HAS A STRONG FEEDBACK ON THURS NIGHT IN SE WY/W SD WITH THE 4-CORNERS S/W INTO THE BLACK HILLS AWAY FROM THE SHEARED/ELONGATED FEATURE PRESENTED BY THE REST OF THE GUIDANCE (PARTICULARLY THE GFS) AND MAY NEED TO BE AVOIDED (PARTICULARLY IN QPF) IN THIS AREA...OTHERWISE SEEMS TO MATCH WELL. THE 00Z UKMET IS VERY FAST/STRONG WITH THE 4-CORNERS S/W AWAY FROM THE SLOWER TREND SEEN IN THE RUN TO RUN ENSEMBLE SUITE. LIKEWISE THE 00Z CMC IS FASTER/FURTHER EAST WITH THE TROF AXIS BUT NOT AS VIGOROUS AS THE UKMET. ALL CONSIDERED CONFIDENCE IS SLIGHTLY BELOW AVERAGE GIVEN THE VARIABILITY AND LOWER PREDICTABILITY PATTERN WITH ALL THE MOVING PARTS...STILL A BLEND OF THE 12Z NAM/GFS AND 00Z ECMWF SEEMS WELL SUITED AS A GOOD COMPROMISE WITHIN THE ENSEMBLE SUITE. WEAK SHORTWAVE CENTERS WITHIN BASE OF BROAD TROF OVER CA/GREAT BASIN THAT EVENTUALLY SETTLES SOUTH AND WEST IN S CA/OFFSHORE WATERS BY FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/00Z ECMWF BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE SHORTWAVE LOW NEAR N CA REMAINS RELATIVELY STATIONARY THROUGH WED EVENING UNTIL SOME ENERGY IS SHED OVER THE TOP OF THE RIDGE DESCENDING ALONG THE WA/OR COAST TO REINFORCE THE TROUGH INCREASING THE POSITIVE TILT TO THE LARGER SCALE TROF IN THE WEST. THE 12Z NAM REMAINS THE STRONGER/DEEPER SOLUTION WITH CLOSER PROXIMITY TO THE ECMWF/12Z GFS AND 00Z ECENS MEAN/06Z GEFS MEAN. THIS IS OPPOSED TO A WEAKER SOLUTION PRESENTED BY THE 00Z CMC/UKMET THOUGH APPEAR TO HAVE SIMILAR SHAPE AND PLACEMENT. THIS PROVIDES SOME CONFIDENCE (SLIGHTLY ABOVE AVERAGE) IN THE OVERALL PATTERN FAVORING A BLEND OF THE 12Z GFS AND 00Z ECMWF TO BEST REPRESENT THE MODEL SUITE. 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