MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 306 AM EDT TUE AUG 05 2014 VALID AUG 05/0000 UTC THRU AUG 08/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION AND FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. SLOWLY PROGRESSING UPPER TROUGH ACROSS THE GREAT LAKES/NORTHEAST COASTAL BAROCLINIC ZONE/POTENTIAL SURFACE WAVE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THERE IS NOW GOOD AGREEMENT AMONG THE LATEST MODELS CONCERNING THE EVOLUTION OF THE UPPER TROUGH SLOWLY MOVING EWD ACROSS THE GREAT LAKES AND NORTHEAST...AS WELL AS WEAK LOW PRESSURE TRACKING NWD FROM OFF THE GEORGIA COAST. IN ADDITION...THERE IS GOOD MODEL AGREEMENT COMPARED WITH THE NHC 03Z ADVISORY TRACK FOR BERTHA. MEAN MID LEVEL TROUGH FROM THE GREAT BASIN TO SOUTHERN CALIFORNIA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE MOST OF THE OPERATIONAL MODELS ARE CONSISTENT WITH THE GFS AND ECMWF ENSEMBLES IN MAINTAINING A MODERATELY WELL DEFINED TROUGH AXIS THAT DRIFTS INTO UTAH BY THURSDAY...WHILE A SEPARATE SHORTWAVE ROTATES WESTWARD INTO CALIFORNIA BEGINNING TONIGHT AND THEN DROPS TOWARD SOUTHERN CA. THESE TWO FEATURES YIELD A POSITIVELY TILTED LARGER SCALE TROUGH BY THURSDAY. THE LATEST AVAILABLE MODELS SHOW DECENT AGREEMENT HERE. LOW-MID LEVEL SHORTWAVE IMPACTING THE N-CNTRL U.S. THROUGH THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF/UKMET CONFIDENCE: BELOW AVERAGE THE 00Z NAM CONTINUES TO BE STRONGER AND FASTER WITH A SURFACE LOW FORECAST TO TRACK EWD FROM THE PLAINS MON NIGHT COMPARED TO THE REMAINING MODEL CONSENSUS. THE 00Z GFS APPEARS TO HAVE SOME FEEDBACK ACROSS NORTH DAKOTA TODAY WHICH CONTAMINATES ITS SOLUTION. THE 00Z CMC APPEARS TOO FAR NORTH WITH THE LOW LEVEL FRONTAL WAVE ACROSS THE MISSISSIPPI VALLEY ON THU. ON THE GOOD SIDE...THE 00Z ECMWF APPEARS LIKE A REASONABLE SOLUTION GIVEN IT HAS INCREASED THE STRENGTH OF THE SHORTWAVE TRACKING THROUGH THE DAKOTAS EARLY IN THE SHORT RANGE...MATCHED NEXT CLOSELY BY THE 00Z UKMET. THE 00Z UKMET HAS SLOWED DOWN THE SPEED OF A SURFACE LOW MOVING THROUGH THE MIDWEST THU NIGHT COMPARED TO ITS 12Z RUN...AND BLENDING THE ECMWF/UKMET ALIGNS REASONABLY WITH THE 12Z ECMWF MEAN AND FALLS IN BETWEEN THE PREFERRED 18/00Z GEFS AND 12Z EC MEANS. GIVEN THE ABOVE AVERAGE SPREAD IN THE MODELS AND POOR RUN TO RUN CONTINUITY...CONFIDENCE IS REDUCED FROM NORMAL. LOW AMPLITUDE SHORTWAVE DIGGING TOWARD THE PAC NW BY THU EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z NAM/UKMET/CMC CONFIDENCE: SLIGHTLY BELOW AVERAGE MODEL DIFFERENCES REMAIN LARGELY IN THE FORM OF TIMING BY FRI MORNING ACROSS THE PAC NW...WITH THE 00Z ECMWF FASTEST...AND THE 00Z GFS SLOWEST. THE SOMEWHAT AMPLIFIED NATURE TO THE FLOW UPSTREAM IS LESS SUPPORTIVE OF A QUICKER TRACK WITH THIS SYSTEM AND THE ENSEMBLE MEANS SUPPORT SOMETHING IN THE MIDDLE OF THE FASTER AND SLOWER CAMPS...BEST REPRESENTED BY THE 00Z NAM/UKMET/CMC. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO