MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 245 AM EDT MON MAR 17 2014 VALID MAR 17/0000 UTC THRU MAR 20/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. UPPER TROUGH REACHING THE PLAINS TUE MORNING SURFACE LOW MOVING THROUGH THE UPPER MIDWEST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 00Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE THE BIGGEST DIFFERENCES WITH THIS SYSTEM REMAIN TO BE NORTH/SOUTH PLACEMENT OF THE LOW LEVEL LOW AND STRENGTH IN THE MID LEVELS. THE 00Z NAM IS THE STRONGEST OF THE DETERMINISTIC SUITE IN THE 700-500 MB LAYER BUT COMPARES FAVORABLY TO THE GFS AT THE SURFACE. THE NAM/GFS/GEFS/SREF AGREE AS ONE GROUP OF OUTCOMES...NORTH WITH THE 850 MB LOW ACROSS THE PLAINS...WHILE THE 12Z ECMWF/UKMET/CMC/EC MEAN AGREE AS ANOTHER OUTCOME...A BIT SOUTH OF THE NCEP CAMP. THE GFS HAS TRENDED IN THE DIRECTION OF THE RELATIVELY CONSISTENT ECMWF OVER ITS PAST 3 RUNS (CONSIDERING 00/12Z ONLY)...BUT THE 12 ECMWF APPEARS A BIT TOO WEAK AT 500 MB CONSIDERING THE LATEST EC/GEFS/CMC ENSEMBLES. THE 00Z ECMWF HAS TRENDED SLIGHTLY IN THE DIRECTION OF THE 00Z GFS...BUT DIFFERENCES REMAIN BETWEEN THE TWO MODELS...THEREFORE AN EVEN GFS/ECMWF BLEND APPEARS MOST WARRANTED...WITH NEITHER SOLUTION IDEAL. SHORTWAVE MOVING BY THE OHIO VALLEY/NORTHEAST MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE MODELS HAVE CONVERGED ENOUGH SUCH THAT REMAINING DIFFERENCES CAN BE RESOLVED WITH A GENERAL MODEL COMPROMISE. UPPER TROUGH/LOW MOVING ALONG THE GULF/SOUTHEAST COASTS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-00Z NAM COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE POOR RUN-TO-RUN CONTINUITY CONTINUED WITH THIS SYSTEM UNTIL TONIGHTS 00Z GUIDANCE WHICH SEEMS TO SHOW SOME STABILITY COMPARED TO PREVIOUS 12Z RUNS BUT THERE WAS A STRONG CONSENSUS TO TREND QUICKER IN ALL OF THE DETERMINISTIC GUIDANCE THROUGH THE 12Z/16 GUIDANCE. CURRENTLY BY TUE MORNING ACROSS THE SOUTHEAST...THE NAM IS THE SLOWEST...WITH THE 00Z ECMWF/UKMET/CMC SHOWING A SIMILAR AND 00Z GFS SLIGHTLY AHEAD OF THE PACK. DIFFERENCES OUTSIDE OF THE NAM ARE SMALL. ENSEMBLE SPAGHETTI HEIGHT PLOTS OF THE 564 DM LINE INDICATE A RANGE IN THE UPPER TROUGH AXIS AT 12Z/18 FROM APALACHICOLA FL TO THE 12Z UKMET POSITION ABOUT 100 MI EAST OF SAVANNA GA. GIVEN CONVERGENCE IN THE LATEST GUIDANCE OUTSIDE OF THE NAM...A NON-NAM COMPROMISE IS PREFERRED. SHORTWAVE/COLD FRONT APPROACHING THE PAC NW WED MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 00Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE THE GUIDANCE HAS BEEN WOBBLING WITH EACH RUN BETWEEN FASTER AND SLOWER WITH THE UPPER TROUGH AS IT NEARS THE PACIFIC NORTHWEST TUE EVENING...WITH THE 00Z NAM ON THE FASTER SIDE OF THE GUIDANCE. THERE ARE DIFFERENCES UPSTREAM WITH AN UPPER TROUGH MOVING INTO THE ALEUTIANS...AND THE UPPER RIDGE TO ITS EAST...BUT THESE DIFFERENCES DO NOT CORRELATE WELL TO THE PACIFIC NORTHWEST. THE 00Z UKMET HAS SLOWED DOWN COMPARED TO ITS 12Z RUN AND THE 00Z ECMWF HAS SPED UP SLIGHTLY TO THE GFS...VERY SIMILAR TO ITS CONSISTENT ECMWF ENSEMBLE MEAN. THE PREFERENCE IS TO BE TOWARD THE SLOWER SIDE GIVEN THE CONSISTENCY WITH THE EC MEAN AND GROWING RIDGE UPSTREAM...BLENDED WITH THE SIMILAR 00Z GFS. THE 00Z GEFS APPEARS SIMILAR TO THE 00Z GFS. CONFIDENCE REMAINS A BIT BELOW AVERAGE DUE TO THE CURERNT MODEL SPREAD. www.wpc.ncep.noaa.gov/html/model2.shtml... OTTO