MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 259 AM EDT SUN MAR 26 2017 VALID MAR 26/0000 UTC THRU MAR 29/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...CLOSED LOW CROSSING THE MID MS/OH VALLEYS SUN... ...SYSTEM WEAKENING INTO THE GREAT LAKES/NORTHEAST THROUGH MON... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM THROUGH MON AS IT LIFTS TOWARD THE GREAT LAKES AND NORTHEAST AND GRADUALLY DAMPENS OUT. A GENERAL MODEL COMPROMISE WILL BE PREFERRED. ...NORTHERN STREAM TROUGH EXITING THE NORTHERN ROCKIES... ...EJECTING ACROSS THE NORTHERN PLAINS/UPPER MIDWEST SUN/MON... ...REACHING THE ONTARIO/QUEBEC BORDER TUES EVENING... ...POSSIBLE SHORTWAVE PHASING OVER NEW ENGLAND BY WED... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z UKMET AND 00Z GEFS MEAN CONFIDENCE: BELOW AVERAGE THE MODELS ADVERTISE THE NORTHERN STREAM COMPONENT OF A LARGER SCALE WESTERN U.S. TROUGH EJECTING OUT OF THE NORTHERN ROCKIES AND ADVANCING PROGRESSIVELY EASTWARD ACROSS SOUTHERN CANADA AND THE FAR NORTHERN PLAINS/UPPER MIDWEST REGION THROUGH SUN AND MON. BY LATE TUES...THE ENERGY WILL BE MOVING ACROSS ONTARIO AND QUEBEC AND POTENTIALLY AMPLIFYING ACROSS NEW ENGLAND BY WED. THE KEY TO A MORE AMPLIFIED SOLUTION IS THE POTENTIAL FOR SOME SHORTWAVE PHASING AS REMNANT SOUTHERN STREAM ENERGY LIFTS NORTHEAST ACROSS THE OH VALLEY/NORTHEAST MON AND TUES. THE 00Z CYCLE OF THE GFS CONTINUES TO STAND OUT SIGNIFICANTLY AS A DEEPER SOLUTION...WITH A STRONGER SURFACE LOW EJECTING OUT OF THE OH VALLEY AND MUCH MORE DEEPENING OVER NEW ENGLAND. THE 00Z NAM TENDS TO SUPPORT A WEAKER VERSION OF THE GFS...BUT THE 00Z ECMWF AND ESPECIALLY THE 00Z CMC ARE FLATTER WITH THE ENERGY WITH LITTLE IF ANY PHASING. THE 00Z UKMET AND TO SOME EXTENT THE 00Z ECMWF HOWEVER DID TREND MORE AMPLIFIED AND ACTUALLY THE UKMET IS ONLY A LITTLE WEAKER THAN THE GFS. THE GFS AND UKMET DO HAVE SUPPORT FROM A LARGE NUMBER OF GEFS MEMBERS...BUT THE EARLIER EURO AND CANADIAN MEMBERS WERE GENERALLY MUCH FLATTER THAN THE GEFS MEMBERS. SINCE THE GFS IS OVERALL STILL A BIT OF A STRONG OUTLIER AND THE CMC A WEAK OUTLIER...A COMPROMISE IN BETWEEN WILL BE PREFERRED...HOWEVER AT THIS POINT THE MODEL CONSENSUS IS STRONGER THAN THE PREVIOUS MODEL CONSENSUS. THE SLIGHTLY WEAKER 00Z UKMET AND 00Z GEFS MEAN WILL BE PREFERRED AS A BLEND...WHICH WILL SUPPORT THE BELIEF THAT LATER RUNS OF THE ECMWF WILL GRADUALLY TREND A BIT STRONGER WHILE THE GFS TRENDS PERHAPS JUST A TAD WEAKER. CONFIDENCE IS VERY LIMITED. ...SOUTHERN STREAM UPPER TROUGH CURRENTLY OVER THE FOUR CORNERS... ...ENERGY EJECTING INTO THE CNTRL/SRN PLAINS SUN NIGHT/MON... ...SYSTEM WEAKENING INTO THE OH VALLEY/NORTHEAST MON NIGHT/TUES... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z UKMET AND 00Z GEFS MEAN CONFIDENCE: AVERAGE...BECOMING BELOW AVERAGE BY END OF PERIOD THE MODELS ARE IN VERY GOOD AGREEMENT WITH THIS SYSTEM THROUGH ABOUT 36 HOURS...HOWEVER SOME IMPORTANT TIMING DIFFERENCES ARE NOTED THEREAFTER AS THE SYSTEM EXITS THE MID MS VALLEY AND MOVES INTO THE OH VALLEY AND EVENTUALLY THE NORTHEAST. THE 00Z GFS WHICH HAD TENDED TO BE THE FASTEST SOLUTION WITH THIS SYSTEM ONCE IT REACHES THE OH VALLEY IS GAINING SOME SUPPORT TO BE MORE PROGRESSIVE FROM THE 00Z UKMET AND ALREADY HAS SUPPORT FROM A MORE PROGRESSIVE 00Z NAM SOLUTION. THE 00Z CMC REMAINS THE SLOWEST SOLUTION BUT HAS TRENDED FASTER...AND THE 00Z ECMWF IS A LITTLE MORE PROGRESSIVE TOO BUT STILL LAGS THE NAM/GFS/UKMET CLUSTER. THE 00Z GFS IN ITSELF MAY ALSO STILL BE A TAD TOO STRONG WITH ITS SURFACE WAVE AND ACTUALLY THE 00Z GEFS MEAN IS A TAD WEAKER AND VERY CLOSE TO THE 00Z UKMET SOLUTION. WILL FAVOR A SOMEWHAT MORE PROGRESSIVE SOLUTION BASED ON THE LATEST TRENDS AND SUGGEST A COMPROMISE BETWEEN THE UKMET AND GEFS MEAN AT THIS POINT WHICH REFLECTS JUST A SLIGHTLY WEAKER VERSION OF THE GFS. ...UPPER TROUGH/COLD FRONT REACHING THE WEST COAST SUN... ...WEAKER NORTHERN STREAM TROUGH OVER THE NORTHWEST MON/TUES... ...CLOSED LOW EVOLUTION INTO THE SOUTHWEST MON/TUES... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT WITH THE INITIAL ARRIVAL OF AN UPPER TROUGH AND COLD FRONT ACROSS THE WEST COAST ON SUN. HOWEVER...ON MON AND TUES...THE ARE IN VERY GOOD AGREEMENT WITH THE DEVELOPMENT OF A RATHER STRONG UPPER TROUGH AND ASSOCIATED CLOSED LOW THAT WILL DROP DOWN THROUGH THE SOUTHWEST AND INTO THE FOUR CORNERS REGION. THE HEIGHT FALLS WILL BE ENCROACHING ON THE SOUTHERN HIGH PLAINS BY WED. MEANWHILE...THE MODELS SHOW A WEAKER NORTHERN STREAM COMPONENT OF THE ORIGINAL TROUGH CROSSING THE NORTHWEST U.S. AND EJECTING OUT INTO THE NORTHERN HIGH PLAINS BY TUES AND WED. THE 00Z NAM APPEARS TO BE A TAD STRONGER WITH THE SOUTHERN STREAM HEIGHT FALLS COMPARED TO THE 00Z GLOBAL MODELS AT THIS POINT WHICH ARE WELL CLUSTERED. FARTHER NORTH...THE 00Z NAM IS NOW JUST SLIGHTLY WEAKER THAN THE SAME MODEL CONSENSUS. THEREFORE...COLLECTIVELY BASED ON BETTER MODEL CLUSTERING AND ENSEMBLE SUPPORT...A NON-NAM CONSENSUS WILL BE PREFERRED WITH THE NORTHERN AND SOUTHERN STREAM COMPONENTS OF THIS SYSTEM. ...COLD FRONT WEAKENING INTO BRITISH COLUMBIA ON TUES... ...ONSHORE FLOW INTO THE PACIFIC NORTHWEST THROUGH TUES... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: AVERAGE THE 00Z CMC AND 00Z UKMET BOTH ARE STILL A BIT STRONGER THAN THE 00Z GFS AND 00Z ECMWF WITH THIS SYSTEM. THE 00Z NAM THOUGH IS A BIT OF A WEAK OUTLIER. GIVEN THE WEAKER ENSEMBLE SUPPORT...WILL FAVOR A CONSENSUS OF THE GFS AND ECMWF AT THIS POINT. ...SHORTWAVE/SURFACE LOW NEAR THE PACIFIC NORTHWEST BY WED... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-GFS CONSENSUS...WEIGHTED TOWARD 00Z UKMET/00Z ECMWF CONFIDENCE: AVERAGE THE MODELS HAVE A SHORTWAVE AND ASSOCIATED WEAK SURFACE LOW/FRONT ARRIVING ACROSS THE PACIFIC NORTHWEST ON WED WITH A PARTICULAR FOCUS ON THE OLYMPIC PENINSULA. THE 00Z GFS IS A STRONGER OUTLIER WITH THIS SYSTEM...AND SHOWS STRONGER ONSHORE FLOW IMPACTING THE OLYMPIC PENINSULA COMPARED TO ANY OTHER MODEL. GENERALLY THE BETTER MASS FIELD CLUSTERING RESIDES WITH THE 00Z UKMET AND 00Z ECMWF...SO A NON-GFS CONSENSUS WILL BE PREFERRED BUT WITH MORE WEIGHTING TOWARD THE UKMET/ECMWF SOLUTIONS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON