MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 149 PM EST SAT MAR 01 2014 VALID MAR 01/1200 UTC THRU MAR 05/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ STRONG SYSTEM IN THE SOUTHWEST TONIGHT...SHEARING TOWARD THE EAST COAST SUN/MON SURFACE LOW DEVELOPING ALONG THE ARCTIC FRONT IN THE SOUTHEAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z NAM/12Z GFS/00Z ECMWF BLEND CONFIDENCE: AVERAGE THE 12Z NAM HAS CONTINUED TO TREND SLOWER...STRONGER AND LESS SHEARED WITH THE SRN STREAM SHORTWAVE AS IT REACHES THE MISSISSIPPI VALLEY MON MORNING...WHICH IS AROUND THE TIME MODEL BEGIN TO SHOW DIFFERENCES. THE 12Z UKMET/CMC/ECMWF HAVE NOT CHANGED MUCH FROM THEIR PREVIOUS 00Z CYCLES...BUT THE UKMET/CMC REMAIN SLOWER AND SOUTH WITH THE SHORTWAVE...VERSUS THE MORE AGREEABLE NAM/GFS/ECMWF AND GEFS/EC MEANS. THE GFS/ECMWF HAVE HELD THE BEST RUN-TO-RUN CONTINUITY SINCE YESTERDAY (CONSIDERING 12/00Z ONLY)...WHICH HELPS TO INCREASE CONFIDENCE IN THEIR SOLUTIONS. THE NAM/GFS/ECMWF ALSO CONTINUE TO HAVE BETTER AGREEMENT TO THE ENSEMBLE SCATTER LOW PLOTS VERSUS THE CMC/UKMET. SHORTWAVE CLIPPING THE NRN GREAT LAKES/NRN NEW ENGLAND THIS WEEKEND ARCTIC FRONT CROSSING NEW ENGLAND AND THE NRN MID-ATLANTIC ON SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/ECMWF CONFIDENCE: AVERAGE THERE IS MUCH BETTER AGREEMENT IN THE GUIDANCE TODAY COMPARED TO YESTERDAY...BUT THE 12Z GFS REMAINS QUICKEST WITH THE COLD FRONT ON SUN...WITH THE 00Z UKMET SLOWEST. THE FASTER (SLOWER) GUIDANCE HAS BEEN SLOWER (FASTER) RESPECTIVELY...ADJUSTING TOWARD A MIDDLE CONSENSUS NEAR THE 12Z NAM / 00Z ECMWF. THE 12Z ECMWF HAS TRENDED SLIGHTLY IN THE DIRECTION OF THE GFS...AND THE NAM APPEARS TO BE A LITTLE SLOW BRINGING COLDER AIR NEAR 850 MB SOUTHWARD THROUGH THE MID-ATLANTIC REGION. GIVEN THE GFS/ECMWF APPEAR TO HAVE BEEN HANDLING THIS SYSTEM BEST...GOING BACK 24-48 HOURS AGO...THE ECMWF TREND TOWARD THE GFS APPEARS REASONABLE...GIVEN THE EARLIER GFS-ECMWF DIFFERENCES WERE SMALL. FOR WHAT IT IS WORTH...THE 09Z SREF MEAN APPEARS TOO COARSE WITH ITS MEAN SOLUTION...APPEARING TOO FAR NORTH/SLOW WITH THE FRONT AND TOO HIGH WITH MID-LEVEL HEIGHTS TUE MORNING. BETTER MODEL CONVERGENCE ALLOWS CONFIDENCE TO REMAIN AVERAGE. UPPER LOW OVER WESTERN CANADA SUN THROUGH TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF/UKMET/CMC BLEND CONFIDENCE: A LITTLE BELOW AVERAGE BY MON...THE 12Z NAM HAS TRENDED INLAND WITH A CLOSED LOW OVER BRITISH COLUMBIA AND IS MUCH CLOSER TO THE REMAINING MODEL CONSENSUS. THE 12Z GFS HOWEVER...HAS WEAKENED ITS UPPER LOW AND DOES NOT CURRENTLY HAVE SUPPORT NOR FIT THE SHAPE IN THE 528 DM ENSEMBLE SPAGHETTI HEIGHT CONTOURS. BY TUE EVENING...THE NAM ELONGATES AND ENLARGES THE UPPER LOW AND ALSO APPEARS A BIT MORE AGGRESSIVE WITH A SHORTWAVE IN THE EASTERN PACIFIC NEAR 140 W...WEST OF THE WA/OR COAST...COMPARED TO THE REMAINING MODEL CONSENSUS. ENSEMBLE MEANS AND TRENDS SUPPORT A SOLUTION CLOSE TO THE ECMWF/UKMET/CMC. POSSIBLE WEAK SHORTWAVE APPROACHING THE RIO GRANDE VALLEY ON TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/12Z ECMWF BLEND CONFIDENCE: BELOW AVERAGE THE MODELS SHOW A WIDE RANGE OF SOLUTIONS WITH A WEAK MID-LEVEL SHORTWAVE THAT AMPLIFIES INTO THE SOUTHWEST DOWNSTREAM OF A BUILDING UPPER RIDGE OFF OF THE SOUTHWEST COAST. THE NAM IS THE MOST DEVELOPED WITH THE SHORTWAVE AND ON THE SOUTHERN EDGE OF THE MODEL SPREAD...WITH STRONG MOISTURE RETURN INTO TEXAS. THE 12Z GFS IS A WEAKER VERSION OF THE 12Z NAM...AND THE 12Z ECMWF ADJUSTED SLOWER/SOUTH TOWARD THE GFS ALONG WITH A TREND TOWARD THE GFS BY THE 12Z CMC. THE 12Z UKMET REMAINS UNCHANGED FROM ITS 00Z RUN. THE GEFS/EC MEANS SUPPORT SOMETHING CLOSE TO THE GFS AND ECMWF...BUT CONFIDENCE IS LOW DUE TO LITTLE AGREEMENT SEEN IN THE MODELS. www.wpc.ncep.noaa.gov/html/model2.shtml... OTTO