MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1144 AM EST TUE MAR 04 2014 VALID MAR 04/1200 UTC THRU MAR 08/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...SHORTWAVE ENERGY SLIDING FROM THE SOUTHERN PLAINS TOWARD THE SOUTHEASTERN U.S. THROUGH 05/1800Z... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE AN ELONGATED MID-LEVEL TROF SITUATED OVER THE SOUTHERN PLAINS HAS SPREAD LIGHT WINTRY PRECIPITATION ACROSS THE WESTERN GULF COAST GIVEN THE ARCTIC AIR IN PLACE. THE ENERGY IS FORECAST TO LIFT NORTHEASTWARD TOWARD THE CAROLINAS AS A SUBTROPICAL RIDGE ANCHORS SOUTH FL/BAHAMAS/CUBA. THE DISORGANIZED AXIS OF SHORTWAVE ENERGY HAVE SOME DIFFERENCES AMONG THE GUIDANCE BUT DO NOT FEEL IT IS LARGE ENOUGH TO DISMISS ANY ONE MODEL. WILL FAVOR A GENERAL MODEL COMPROMISE TO ACCOUNT FOR ANY SMALL-SCALE ISSUES. ...STRONG AXIS OF HEIGHT FALLS DROPPING THROUGH NEW ENGLAND BY LATE WEDNESDAY... PRELIMINARY PREFERENCE: BLEND OF THE 12Z NAM/GFS FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE A STRONG LOBE OF ENERGY PEELING OFF A BROAD CYCLONIC FLOW ACROSS THE HIGHER LATITUDES WILL AFFECT NEW ENGLAND BY LATE WEDNESDAY. AMONG THE SLOWER OF THE MODELS ARE THE 00Z CMC/ECMWF/ECMWF ENSEMBLE MEAN WHILE THE 00Z UKMET AND 06Z GEFS/09Z SREF MEANS ARE ON THE FASTER SIDE. SOMEWHERE IN THE MIDDLE ARE THE 12Z NAM/GFS. THE PAST SEVERAL CYCLES OF MOST MODELS SUGGEST A TREND IN THE FASTER DIRECTION. NOT SURE OF GOING AS FAST AS THE QUICKEST MODELS SO WILL COMPROMISE AND STAY CLOSER TO THE MIDDLE. THE PREFERENCE WILL BE A BLEND OF THE 12Z NAM/GFS. ...WELL-DEVELOPED UPPER LOW CROSSING THE OZARKS BY 06/1200Z... ...INITIAL SURFACE WAVE IN THE GULF OF MEXICO... ...COASTAL LOW DEVELOPING ALONG THE SOUTHEASTERN U.S. COAST... PRELIMINARY PREFERENCE: BLEND OF THE 00Z UKMET WITH THE 00Z ECMWF/ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE SHORTWAVE ENERGY EJECTING OUT OF THE CENTRAL GREAT BASIN/ROCKIES WILL EVENTUALLY CARVE OUT A FAIRLY SIGNIFICANT UPPER TROF...POSSIBLY AS A CLOSED LOW...AS IT CROSSES THE OZARKS BY EARLY THURSDAY MORNING. EARLY ON...THE 12Z GFS AND 00Z ECMWF/UKMET ARE IN NEAR AGREEMENT WITH THE EVOLUTION WHILE THE 12Z NAM IS SLOWER/MORE WESTWARD AND THE 00Z CMC HAS A MORE ELONGATED TROF AXIS. AT THIS TIME...06/1200Z...MODELS INDICATE AN AREA OF LOW PRESSURE WILL DEVELOP IN THE CENTRAL/EASTERN GULF OF MEXICO WITH MODEL SPREAD FAIRLY HIGH INCLUDING ENSEMBLE MEANS WHICH DISAGREE WITH ONE ANOTHER. THE SURFACE LOW PLACEMENTS GENERALLY FOLLOW THE DIFFERENCES SEEN ALOFT. AS THE UPPER TROF SLIDES FURTHER EAST...THE 12Z GFS BEGINS TO SLOW DOWN AND ENDS UP SLOWER THAN ITS 06Z GEFS MEAN ALONG WITH EXITING THE CONSENSUS BETWEEN THE 00Z ECMWF/UKMET. MEANWHILE...THE 12Z NAM REMAINS DECIDEDLY SLOWER AND CLOSES OFF THE UPPER LOW OVER THE SOUTHERN APPALACHIANS. WITH REGARD TO THE COASTAL LOW DEVELOPMENT...IT APPEARS A LARGE AMOUNT OF THE 00Z ECMWF ENSEMBLE MEMBERS ARE NORTH AND EAST OF THE 00Z ECMWF RUN. THE 00Z ECMWF IS MORE AGGRESSIVE DURING THE STAGE OF CYCLOGENESIS WHICH HELPS THE LOW WRAP UP AND END ON THE WESTERN SIDE OF THE SPREAD. DO LIKE THE WAY THE 00Z ECMWF/UKMET HANDLE THE EVOLUTION OF THE SYSTEM BUT WILL ADD THE 00Z ECMWF ENSEMBLE MEAN IN ORDER TO ACCOUNT FOR THE 00Z ECMWF BEING WEST OF THE CONSENSUS HERE. WILL HOLD THE FORECAST CONFIDENCE AT BELOW AVERAGE GIVEN THE VAST SPREAD BETWEEN THE SLOWEST/FASTEST GUIDANCE. ...PROGRESSIVE PACIFIC SYSTEM ADVANCING THROUGH THE PACIFIC NORTHWEST EARLY THURSDAY... ...EVENTUALLY CARVING OUT A MEAN TROF ACROSS THE ROCKIES BY LATE IN THE WEEK... PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF FORECAST CONFIDENCE: BELOW AVERAGE QUASI-ZONAL FLOW SETTING UP ACROSS MUCH OF THE EASTERN PACIFIC WILL ALLOW A FAST-MOVING PACIFIC SYSTEM TO PUSH INTO THE PACIFIC NORTHWEST BY LATE WEDNESDAY/EARLY THURSDAY. AS THE SYSTEM MOVES INLAND...THE 12Z NAM IS THE WEAKEST ALOFT WHICH LEADS TO A MUCH LESS DEFINED SURFACE LOW MOVING TOWARD VANCOUVER ISLAND. ADDITIONALLY...THE 00Z UKMET IS A BIT SLOWER WITH THE PROGRESSION OF THIS SYSTEM AND IS ALSO WEST OF THE WELL CLUSTERED ENSEMBLE MEANS. AS THE HEIGHT FALLS EVENTUALLY PROGRESS INLAND AND FORM A MEAN TROF ACROSS THE INTERIOR MOUNTAIN WEST...THE GFS/ECMWF REMAIN AT ODDS WITH ANOTHER WHICH HAS BEEN EVIDENT IN THE PAST SEVERAL RUNS OF EACH MODEL. THE 564-DM SPAGHETTI PLOT DOES NOT OFFER TOO MUCH INSIGHT ALTHOUGH DOES SHOW THERE ARE QUITE A FEW MEMBERS MORE AMPLIFIED THAN THE 00Z ECMWF RUN. GIVEN THE LIMITED CONFIDENCE AT THIS POINT...WILL TAKE A BLEND OF THE MORE MIDDLE GROUND 12Z GFS AND THE FASTER 00Z ECMWF. MIGHT MAKE ADJUSTMENTS TO THIS PREFERENCE PENDING ADDITIONAL 12Z GUIDANCE. ...NEXT SURGE OF COLDER AIR INTO THE NORTH-CENTRAL U.S. BY 08/0000Z... PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF WITH THE 00Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE THE NEXT NORTHERN STREAM TROF LATE IN THE PERIOD SHOULD GENERALLY JUST SKIRT THE NORTHERN PLAINS/UPPER MIDWEST WITH ANOTHER COLD FRONT SWOOPING DOWN IN THE MIDDLE OF THE U.S. AT FIRST GLANCE...THE 12Z NAM IS VERY SLOW WITH THE PLACEMENT OF THIS SYSTEM AND LOOKS VERY MUCH AN OUTLIER. ADDITIONALLY...THE 12Z GFS HAS BACKED OFF ON THE FASTER SOLUTIONS PROVIDED BY THE 06Z GFS/GEFS MEAN. THIS HAS BROUGHT IT CLOSER TO WHAT IS ADVERTISED BY THE 00Z ECMWF/ECMWF ENSEMBLE MEAN. THE WPC PREFERENCE WILL FOLLOW THE 12Z GFS/00Z ECMWF AND THROW IN THE 00Z ECMWF ENSEMBLE MEAN TO ACCOUNT FOR SOME RUN-TO-RUN FLUCTUATIONS SEEN IN THE MODELS. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER