MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 254 AM EDT FRI APR 11 2014 VALID APR 11/0000 UTC THRU APR 14/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 00Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...SYSTEM IN THE NORTHEAST QUARTER OF THE U.S. THROUGH SATURDAY... PREFERENCE: ANY 00Z OPERATIONAL MODEL EXCLUDING THE NAM CONFIDENCE: AVERAGE A MID LEVEL WAVE MOVING THROUGH THE NORTHEAST THIS MORNING AND A SECOND WAVE TO ARRIVE EARLY SATURDAY WILL PUSH A WEAK COLD FRONT THROUGH THE REGION. THE MODELS ARE NOW SIMILAR IN THEIR STRENGTH AND TIMING ALOFT. THE NAM PREDICTS LESSER AMPLITUDE WITH THE SECOND WAVE AND IS THEREFORE NOTICEABLY FASTER IN PUSHING THE FRONTAL ZONE OFFSHORE. ...SOUTHWEST U.S. SYSTEM EJECTING EAST... PREFERENCE: BLEND OF 00Z GFS/ECMWF CONFIDENCE: AVERAGE THERE HAS BEEN LITTLE RUN TO RUN VARIATION REGARDING THIS SYSTEM IN THE GFS/GEFS AND ECMWF/EC ENSEMBLE. THE UKMET IS SIMILAR TO THE GFS/ECMWF THROUGH DAY 2...BUT THEN BECOMES LESS SHARPLY DEFINED AND MOVES THE SOUTHERN STREAM TROUGH/RIDGE PATTERN DOWNSTREAM FASTER THAN CONSENSUS. ON THE CONTRARY...RECENT RUNS OF THE CANADIAN HAVE TENDED TO LAG BEHIND. THE 00Z NAM IS IN VERY CLOSE AGREEMENT WITH THE CONSENSUS...BUT IT DOES BECOME SOMEWHAT FLAT AS THIS WAVE EJECTS INTO THE PLAINS...AND IS QUICKER TO VEER BOUNDARY LAYER WINDS. ...LEAD NORTHERN STREAM SHORTWAVE SAT/SUN... ...SURFACE LOW CROSSING THE GREAT LAKES... PREFERENCE: BLEND OF 00Z ECMWF/UKMET CONFIDENCE: AVERAGE IN SPAGHETTI PLOTS ONLY THE NAM/GFS/GEFS PRODUCE RUNS THAT FORECAST A VERY FLAT AND FAST MOVING SHORTWAVE TROUGH WITH LITTLE HINT OF DOWNSTREAM SHORTWAVE RIDGING. THE GFS AND ESPECIALLY THE NAM FAR OUTPACE THE GLOBAL MODEL AND ENSEMBLE CONSENSUS AFTER DAY 1. THE MODELS HAVE STRUGGLED WITH THIS SYSTEM...AND NO SOLUTION IS YET CONSIDERED IDEAL...BUT THE ECMWF HAS BEEN MUCH STEADIER...AND THE ECMWF ENSEMBLE MEAN THE STEADIEST. WATCHING ENSEMBLE SURFACE LOW PLOTS OVER MULTIPLE MODEL CYCLES...THEY ARE CONVERGING TOWARD A SOLUTION MUCH LIKE THE 00Z ECMWF/UKMET. ...TROUGH DIGGING THROUGH THE ROCKIES SAT/SUN... PREFERENCE: BLEND OF 00Z GFS/ECMWF/CANADIAN CONFIDENCE: AVERAGE HERE THE MODELS ARE BEHAVING IN A MANNER CONSISTENT WITH THEIR BIASES. THE GFS/GEFS ARE GRADUALLY DEEPENING TOWARD THE STRENGTH THAT IS APPEARING WITHOUT VARIATION IN THE ECMWF ENSEMBLE MEAN. THE OPERATIONAL ECMWF IS ONE OF THE STRONGER/DEEPER SOLUTIONS...BUT HAS SUPPORT FROM THE CANADIAN AND A HEALTHY NUMBER OF EUROPEAN AND CANADIAN ENSEMBLE MEMBERS. ...SYSTEM APPROACHING THE PACIFIC NORTHWEST BEYOND DAY 3... PREFERENCE: BLEND OF 00Z NAM/18Z GEFS MEAN CONFIDENCE: BELOW AVERAGE ASIDE FROM THE QUICK AND LOW AMPLITUDE UKMET...THE OPERATIONAL MODELS ARE FORECASTING A CLOSED LOW TO FORM AT THE BASE OF A TROUGH PROGRESSING TOWARD THE NORTHWEST U.S. AND SOUTHWEST CANADA. THERE IS SIGNIFICANT SCATTER IN THE FORECAST POSITION OF THE DEVELOPING LOW. OUR CHOICE OF THE 00Z NAM/18Z GEFS MEAN IS CONSISTENT WITH THE WPC MEDIUM RANGE DESK FORECAST...WHILE HEDGING SLIGHTLY TOWARD THE MORE RECENT NCEP RUNS...WITH CLOSED LOW FORMATION MORE LIKELY AT LOWER LATITUDE THAN SEEN IN THE ECMWF. THIS SYSTEM WILL LIKELY HAVE NO IMPACT THROUGH DAY 3. www.wpc.ncep.noaa.gov/html/model2.shtml... BURKE