MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 157 AM EST MON DEC 07 2015 VALID DEC 07/0000 UTC THRU DEC 10/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING FINAL MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CLOSED LOW TRACKING ACROSS THE OHIO VALLEY TODAY AND EXITING INTO THE WRN ATLANTIC FOR TUE DEVELOPING SURFACE LOW IN THE WRN ATLANTIC BY TUE MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/GFS/ECMWF BLEND CONFIDENCE: AVERAGE ADJUSTMENTS MADE WITH THE 00Z SUITE OF MODELS SHOW THE NAM/GFS/ECMWF TO HAVE DECENT AGREEMENT AND THE 00Z UKMET/CMC HAVE ADJUSTED IN THE DIRECTION OF THE NAM/GFS/ECMWF. WHILE THE 00Z GFS WAS THOUGHT TO BE A BIT NORTH WITH THE PRELIMINARY PREFERENCE...IT NOW LOOKS WITHIN REASON GIVEN THE REMAINING MODELS AGREEMENT REGARDING THE UPPER LOW AND SURFACE LOW TO DEVELOP IN THE WRN ATLANTIC. THE 00Z UKMET/CMC CONTINUE TO HAVE ENOUGH DIFFERENCE FROM THE PREFERENCE REGARDING THE STRENGTH OF THE MID-LEVEL LOW OR WITH PLACEMENT TO LEAVE OUT OF THE PREFERENCE AT THIS TIME. SHORTWAVE REACHING THE CNTRL/NRN PLAINS LATER THIS MORNING AND SHEARING OUT ACROSS NEW ENGLAND BY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z CMC BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE WHILE THE POTENTIAL INTERACTION OF THIS SHORTWAVE WITH WEAKER NEARBY WAVES INFLUENCES THE STRENGTH OF THE ENTIRE FEATURE AS IT CROSSES THE GREAT LAKES REGION...THE 00Z CMC IS UNIQUE IN WEAKENING THE SHORTWAVE PAST 12Z/08 WHILE THE REMAINING MODELS HOLD ONTO A WEAK REFLECTION OF THE SHORTWAVE INTO NRN NEW ENGLAND. NUMEROUS POTENTIAL INTERACTIONS KEEPS CONFIDENCE A BIT BELOW AVERAGE HERE. SHORTWAVE AMPLIFYING ACROSS THE MIDWEST/UPPER MIDWEST TUE NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF BLEND CONFIDENCE: AVERAGE THE 00Z NAM REMAINS WELL NORTH WITH A SHORTWAVE AS IT CROSSES THE ROCKIES INTO THE PLAINS ON TUE...AND IS ON THE VERY NRN EDGE OF THE ENSEMBLE GUIDANCE. THE 00Z GFS/12Z ECMWF HAVE BOTH TRENDED FASTER COMPARED TO YESTERDAY...BUT REMAIN IN GOOD AGREEMENT WITH THE GEFS/ECMWF ENSEMBLE MEANS. THE 00Z ECMWF/UKMET TRENDED MUCH DEEPER WITH THE UPPER TROUGH AS IT MOVES EAST ACROSS THE OHIO/TENNESSEE VALLEYS...AND NOW LIE ON THE SOUTHERN EDGE OF THE ENSEMBLE SPREAD AND ARE NOT PREFERRED GIVEN A LACK OF BETTER SUPPORT FOR THESE DEEPER SOLUTIONS. WHILE ENSEMBLE SPREAD IS SMALLER COMPARED TO YESTERDAY...IT REMAINS MODEST IN THE LATEST ENSEMBLE SPAGHETTI PLOTS...KEEPING CONFIDENCE ONLY AVERAGE. LOW AMPLITUDE SHORTWAVE/SURFACE LOW NEARING THE PACIFIC NORTHWEST WED MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z NAM BLEND CONFIDENCE: AVERAGE WHILE THE DIFFERENCES HERE ARE NOT LARGE BY WED MORNING...THERE HAD BEEN TWO MAIN CAMPS OF MODELS. ONE CAMP SHOWS MORE OF A MERIDIONAL FLOW ON EITHER SIDE OF THE SHORTWAVE...MADE UP OF THE 00Z GFS...12Z UKMET...WHILE THE OTHER CAMP WAS A BIT FLATTER...SHOWN BY THE 00Z NAM...12Z ECMWF/CMC. THE 00Z ECMWF/CMC JOINED THE 00Z GFS/12Z UKMET WITH MORE AMPLIFICATION OF AN UPSTREAM SHORTWAVE. BY 24 HOURS LATER ACROSS THE PLAINS...12Z/10...ONLY THE 00Z NAM STANDS OUT FROM THE MIDDLE OF THE LATEST ENSEMBLE SPREAD. STRENGTHENING CLOSED LOW/UPPER TROUGH APPROACHING THE WEST COAST WED NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z NAM BLEND CONFIDENCE: A BIT BELOW AVERAGE DIFFERENCES ARE WITH THE DETAILS...AS ALL OF THE LATEST DETERMINISTIC MODELS SHOW A SIMILAR EVOLUTION WITH THIS FEATURE. HOWEVER...THE 00Z NAM APPEARS TO BE TOO FAR SOUTH WHILE THE 00Z ECMWF TRENDED NORTH FROM ITS PREVIOUS RUN. DESPITE THE ADJUSTMENT FROM THE 00Z ECMWF...THE 00Z UKMET AND 00Z CMC ARE JOINED WITH THE 00Z GFS IN SHOWING A SIMILAR EVOLUTION BY 12Z/10 ACROSS THE EASTERN PACIFIC. THIS IDEA IS SUPPORTED BY THE LATEST GEFS/EC MEAN POSITIONS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO