MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1241 AM EDT TUE MAR 22 2016 VALID MAR 22/0000 UTC THRU MAR 25/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE WEAK SURFACE WAVE MOVING THROUGH THE NRN/CNTRL PLAINS TODAY AND NEW ENGLAND WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THERE REMAINS SOME MINOR PLACEMENT DIFFERENCES WITH A WEAK SURFACE LOW EXPECTED TO TRACK THROUGH THE GREAT LAKES LATE TUE ALONG THE FRONTAL ZONE INTO NEW ENGLAND EARLY WED. THE PLACEMENT/ORIENTATION OF THE FRONTAL ZONE APPEARS SOLID ENOUGH TO SUPPORT AN OPERATIONAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. UPPER TROF ENTERING THE INTERMOUNTAIN WEST TODAY AND EJECTING INTO THE PLAINS WED LIFTING INTO THE GREAT LAKES THURSDAY WITH ASSOCIATED DEEP SURFACE LOW ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z CMC/UKMET BLEND CONFIDENCE: BELOW AVERAGE LITTLE CHANGE IN THOUGHT OVERALL FAVORING A MIDDLE GROUND SOLUTION BETWEEN THE DISTINCT DIFFERENCES BETWEEN THE FASTER/NORTHERN GFS/GEFS CAMP AND SLOWER/SOUTHWEST ECMWF SOLUTIONS...AND SEEMS TO BE TIED HEAVILY TO INTERACTION WITH NORTHERN STREAM AMPLIFICATION AND/OR SOME ENERGY LINGERING IN THE APEX OF THE SHORTWAVE RIDGING ACROSS AB/SK/MT ATTM WHICH THOUGH BEING SAMPLED...TIMING OF THIS INTERACTION IS YET TO RESOLVE AND THEREFORE PREDICTABILITY OF THE PATTERN IS VERY DIFFICULT TO DISREGARD EITHER CAMP YET CONTINUING TO FAVOR AN OVERALL MIDDLE GROUND. INTERESTINGLY THE OPERATIONAL VERSIONS OF THE GFS AND ECMWF REMAIN ON THE FURTHEST EDGES OF THEIR ENSEMBLE SUITES...THIS WAS EVEN FURTHER EXACERBATED BY THE 00Z GFS WHICH THOUGH WEAKENING THE UPPER LOW/TROF A BIT THROUGH THE PLAINS/MIDWEST...REMAINS FAST AND ALSO ON THE NORTHERN SIDE OF GEFS MEMBERS (INTO QUEBEC VS NORTHERN NEW ENGLAND INTO FRIDAY...KEEPING IT INCONSISTENT WITH LITTLE CONFIDENCE. 00Z NAM ALSO BROKE FROM SOME RUN TO RUN CONSISTENCY...SLOWING THE UPPER LOW AND STRENGTHENING THE SURFACE LOW...WITH BETTER DUAL JET SUPPORT AND FAIRLY STRONG ASCENT KEEPING THE FRONTOGENESIS AXIS IN A SIMILAR PLACE BUT JUST MUCH SLOWER (NEARLY 6HRS). THIS MATCHES A SIMILAR LONGITUDINAL SIMILARITY IN TIMING WITH THE SLOWER 12Z ECMWF WHILE BEING ABOUT HALF A STATE NORTH MORE IN LINE WITH THE SURFACE TRACK OF THE GFS...WHICH MAY SEEM LIKE A COMPROMISE BUT IT ALSO APPEARS TO HAVE LIMITED ENSEMBLE SUPPORT AS THAT IS FURTHER EAST AND SOUTH OVERALL...BEST PRESENTED BY THE 12Z CMC AND POSSIBLY THE 12Z UKMET WHICH WOULD BE ON THE FASTER SIDE...CLOSER TO THE 18Z GEFS MEAN. THE GOOD NEWS IS THE COLD FRONTAL TIMING ACROSS THE SOUTH IS IN MUCH BETTER AGREEMENT OVERALL WITH SMALL DIFFERENCES BY THE END OF DAY THREE ACROSS THE SOUTHEAST (ECMWF LAGGING A BIT TOO MUCH EVEN BY ECENS MEAN STANDARD). AS SUCH NO ONE DETERMINISTIC MODEL FITS THE OVERALL PREFERENCE CLOSE ENOUGH TO HAVE ANYTHING BUT BELOW AVERAGE CONFIDENCE. STILL THE PREFERENCE FAVORS THE MIDDLE GROUND SOLUTIONS IN THE SPREAD: THE 12Z UKMET/CMC BLEND FOR MASS FIELDS. PLEASE REFER TO QPFPFD AND QPFHSD FOR FURTHER QPF/SNOWFALL DETAILS. UPPER LOW SHEDDING ENERGY INTO THE PACIFIC NORTHWEST WITH COLD FRONT REACHING THE PACIFIC NORTHWEST WEDNESDAY NIGHT AND SURFACE CYCLOGENESIS IN HIGH PLAINS BY FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM AND 12Z ECMWF/CMC BLEND CONFIDENCE: ABOVE AVERAGE MODELS ARE IN FAIRLY STRONG AGREEMENT WITH THE OVERALL SHAPE/STRENGTH OF THE UPPER LOW APPROACHING THE ALASKAN PANHANDLE BY EARLY THURS. SHEARING FORCES ALLOW FOR AN ELONGATION ALONG THE SEABOARD OF BC WITH THE SE MOST PORTION OF THE WAVE SHEDDING OFF INTO VANCOUVER ISLAND BY THURS MORNING AND CROSSING THE NW US/CANADA BOARDER AHEAD OF THE REST OF THE UPPER LOW ENERGY THAT BEGINS TO SHEAR/ELONGATE INTO THE INCREASING NORTHWESTERLY FLOW WITH THE BULK REACHING THE JUAN DE FUCA STRAIT BY THE END OF THE FORECAST PERIOD IN FAIRLY STRONG AGREEMENT. THERE REMAIN SMALL TIMING AND STRENGTH DIFFERENCES TO THE LEAD PIECE OF ENERGY THAT REACHES THE HIGH PLAINS LATE THURS INTO FRIDAY LEADING TO SURFACE CYCLOGENESIS. THE LARGEST DIFFERENCES ARE MAINLY SEEN WITH THE PLACEMENT/STRENGTH OF THE SURFACE LOW. THE ECMWF ENSEMBLE ARE MAINLY NORTHERN AND SLIGHTLY STRONGER SURFACE REFLECTIONS WITH THE GEFS/GFS ON THE WEAKER SOUTHERN SIDE. THE 00Z NAM IS A VERY GOOD COMPROMISE/CENTER SOLUTION FOR THE SURFACE LOW BUT IS THE ONLY DETERMINISTIC MODEL OUT EAST WITH THE UPPER WAVE...THE 12Z UKMET IS IN LINE ALOFT BUT UNREALISTICALLY FAST/DEEP IN THE NORTHWEST ANGLE OF MN WITH THE SURFACE LOW. THE 12Z CMC IS ALSO MIDDLE GROUND BUT IS GENERALLY WEAK AT THE SURFACE. THE 00Z GFS DID TREND SLOWER THAN THE 18Z GFS AND GEFS...TO PUT IT OUT OF TIGHTER AGREEMENT. AS SUCH WILL FAVOR THE MOST CENTRAL/CLUSTERED SOLUTIONS FOR ABOVE AVERAGE CONFIDENCE... IN THE 00Z NAM AND 12Z ECMWF/CMC BLEND. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA