MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 243 PM EDT SUN SEP 28 2014 VALID SEP 28/1200 UTC THRU OCT 02/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ WEAK CLOSED LOW/TROUGH MOVING FROM THE MIDWEST TO THE MID-ATLANTIC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE ONLY MINOR MODEL DIFFERENCES REMAIN WITH THIS FEATURE SO A GENERAL MODEL COMPROMISE IS RECOMMENDED TO SMOOTH OUT ANY OF THE SHORT TERM DIFFERENCES. SHORTWAVE TROUGH REACHING THE UPPER GREAT LAKES ON MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS AND THE 12Z ECMWF CONFIDENCE: AVERAGE A SIGNIFICANT TREND HAS BEEN SEEN IN THE GUIDANCE TO BE MORE AMPLIFIED WITH THIS WAVE...MORE LIKE THE ECMWF AS THE UPPER WAVE CROSSES THE GREAT LAKES. THE 12Z UKMET/CMC HAVE MADE MINOR ADJUSTMENTS FROM THEIR 00Z RUNS...SLIGHTLY AWAY FROM THE ECMWF. CURRENTLY...THE 12Z NAM/GFS/CMC REPRESENT A NRN AND SLIGHTLY WEAKER CAMP REGARDING THE MID-LEVEL VORTICITY CENTER OVER THE NRN MID-ATLANTIC REGION WED MORNING...WHILE THE 12Z UKMET/ECMWF ARE SLIGHTLY MORE AMPLIFIED/SOUTH. THE ENSEMBLE MEANS ARE ALSO NOW IN PRETTY GOOD AGREEMENT AND SUPPORT A MIDDLE OF THE ROAD APPROACH...SO GIVEN THE GOOD MODEL AGREEMENT ON TIMING AND REASONABLE AGREEMENT ON STRENGTH...A BLEND OF THE TWO CAMPS APPEARS WARRANTED. THIS IS BEST REPRESENTED BY AVERAGING THE 12Z GFS AND 12Z ECMWF. BROAD UPPER TROUGH/EMBEDDED VORTS OVER THE SOUTHERN PLAINS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF CONFIDENCE: BELOW AVERAGE ALL OF THE MODELS HAVE TRENDED MORE SUPPRESSED SINCE RUNS FROM 12Z/27 AND 00Z/27 WITH A WEAK LOW FORECAST TO TRACK ACROSS THE SOUTHEAST TONIGHT INTO MONDAY AND CONTINUE TO SHOW INCONSISTENCIES ON TIMING...BUT ALSO A TREND TO BE FASTER WITH THE WAVE. THE 00Z ECMWF AND 00Z EC MEAN ARE WEAKEST WITH THE 850-700 MB WAVE...BUT THE NAM/GFS/UKMET/CMC ALL SEEM TO SHOW SOME SIGNS OF CONVECTIVE FEEDBACK. THE ENSEMBLE MEANS SUPPORT THEIR DETERMINISTIC COUNTERPARTS. THE 12Z ECMWF IS LITTLE STRONGER AND SOUTH OF THE 00Z ECMWF CONCERNING THE LOW LEVEL WAVE FORECAST TO TRACK ACROSS THE SOUTHEAST ON MON...WHILE THE 12Z UKMET/CMC REMAIN TOO FAST/STRONG...RESPECTIVELY. THE NAM/SREF CONTINUE TO APPEAR TOO SLOW/STRONG GIVEN THE REMAINING 12Z MODELS AND TRENDS. JUST CONSIDERING MASS FIELDS...THE GFS/ECMWF SEEM MOST USEFUL...THE GFS LIKELY TOO STRONG AND THE ECMWF POSSIBLY TOO WEAK WITH BOTH SHOWING A FAVORABLE TIMING. CONFIDENCE REMAINS LIMITED...AND HI-RES MODEL QPF MAY OFFER A MORE REASONABLE DEPICTION. PLEASE SEE WPC QPF TEXT DISCUSSION PRODUCTS FOR DETAILS ON RAINFALL AMOUNTS. DEEP TROUGH/CLOSED LOW MOVING FROM THE WEST INTO THE N-CNTRL U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z ECMWF/CMC AND 12Z NAM CONFIDENCE: AVERAGE THE MODELS ARE IN DECENT AGREEMENT HERE BUT THERE ARE DIFFERENCES WORTH NOTING...FIRST WITH THE 12Z GFS BEING A BIT STRONGER THAN THE REMAINING MODEL CONSENSUS...AND PROBABLY TOO STRONG. REGARDING TIMING...THE ENSEMBLE MEANS SUPPORT SOMETHING CLOSE TO THE NAM/ECMWF/CMC WITH THE ECMWF LIKELY HOLDING THE BEST MIDDLE GROUND AND CONTINUITY OF THE THREE MODELS. CHANGES FROM THE 00Z ECMWF TO THE 12Z ECMWF WERE TO BE SLIGHTLY EAST WITH THE TRACK OF THE RESULTING SURFACE LOW ACROSS THE PLAINS...BUT WHEN BLENDED WITH THE SIMILAR 12Z CMC AND SRN NAM POSITION...A REASONABLE COMPROMISE IS GENERATED. MID-UPPER TROUGH REACHING THE PACIFIC NORTHWEST MON NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z CMC BLEND CONFIDENCE: AVERAGE THE 12Z CMC APPEARS JUST A BIT MORE AMPLIFIED WITH THE UPPER TROUGH AS IT CROSSES THE CNTRL ROCKIES ON TUE...WITH THE REMAINING AGREEABLE 12Z MODEL CONSENSUS A BIT WEAKER...AND IN LINE WITH THE ENSEMBLE MEANS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO