MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 241 PM EDT SAT MAY 14 2016 VALID MAY 14/1200 UTC THRU MAY 18/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHORTWAVE TROUGH CROSSING THE OH VALLEY SAT...THEN BECOMING A CLOSED MID LEVEL LOW SAT/SUN OVER NEW ENGLAND SURFACE LOW TRACKING ACROSS OH VALLEY TODAY INTO NEW ENGLAND SUN/MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS CONTINUE TO BE FAIRLY WELL PACKED WITH ONLY SMALL DIFFERENCES MAINLY IN AMPLIFICATION/SPACING OF THE SHORTWAVE RIDGING BETWEEN THE LEAD SHORTWAVE CROSSING INTO NEW ENGLAND BY SAT EVENING AND THE DIGGING SHORTWAVE DESCENDING OUT OF THE WESTERN LAKES TODAY EVENTUALLY SUPPORTING A CLOSED MID LEVEL LOW SUN EVENING INTO THE GREAT LAKES. THE GFS AND THEREFORE GEFS ARE ON THE SLOWER/NORTHERN SIDE OF THE GUIDANCE AND RETAIN THE SURFACE LOW CENTER OVER QUEBEC VERSUS TRANSFERRING TO THE NEWER CENTER IN NEW BRUNSWICK BY MON...AS PRESENTED BY THE 00Z ECENS MEMBERS. TIMING SHIFTS ARE MINOR OVERALL TO SUPPORT AN OPERATIONAL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z UKMET SHIFTED A LITTLE SLOWER WITH BOTH THE LEAD WAVE AND SECONDARY WAVE THAT EVENTUALLY CLOSES OFF...MAKING THE UKMET APPEAR TO BE THE OUTLIER IF EVER SO SLIGHTLY. GIVEN THE OTHER STRONGER AGREEMENT WILL EXCLUDE IT IN THE PREFERENCE. SHORT WAVE CROSSING THE UPPER GREAT LAKES SUN/MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/ECMWF BLEND CONFIDENCE: BELOW AVERAGE MODELS ARE CONFIDENT IN EVOLUTION OF THE SPLIT OF THE UPPER LEVEL LOW OVER WESTERN HUDSON BAY THOUGH DUE TO INTERACTIONS IN THIS HIGHLY SHEARED ENVIRONMENT AND PARTLY DUE TO TIMING OF THE EXIT OF THE CLOSED MID-LEVEL LOW IN EASTERN CANADA THERE IS INCREASING SPREAD IN TIMING SHAPE AND STRENGTH OF THE TROF THAT IS FORECAST TO DESCEND INTO THE WESTERN LAKES SUN/MON. CONSISTENCY UTILIZING THE LAST FEW DAYS OF ENSEMBLE SPREAD HAS BEEN FAVORING A TREND TOWARD A FASTER/FLATTER/ELONGATED TROF ACROSS THE GREAT LAKES BY THE END OF THE FORECAST PERIOD. THERE IS/WAS A SLIGHT HINT WITH A FASTER EXITING OF THE WAVE TO HAVE SOME CONSOLIDATION TOWARD A SYMMETRIC/POTENTIALLY CLOSED LOW. THIS IS PRESENTED BY THE 00Z UKMET BUT MUCH SLOWER AND FURTHER NORTHWEST THAN ANY OTHER ENSEMBLE MEMBER WITHIN THE GEFS/ECENS/CMCE SUITE. THE 12Z NAM TRENDED THIS DIRECTION AS WELL AND WHILE THE 06Z GFS HINTED AT THIS SOLUTION AS WELL THE 12Z GFS IS MORE IN LINE WITH THE EARLIER PREFERENCE AND 06Z GEFS/00Z ECENS MEAN AND 00Z ECMWF AND 00Z CMC. AS SUCH WILL FAVOR A 12Z GFS/00Z ECMWF BLEND; HOWEVER THE CONFIDENCE REMAINS BELOW AVERAGE GIVEN THE LARGE VARIATION IN THE SOLUTIONS AND RUN TO RUN VARIATIONS. 19Z UPDATE: THE TREND SUGGESTED BY THE 12Z GFS/NAM TOWARD SLIGHTLY SLOWER CONTINUED WITH THE 12Z ECMWF/CMC...AND THOUGH THE ECMWF CLOSES A LOW IN THE CENTRAL GREAT LAKES BY TUES LIKE THE NAM...IT REMAINS MORE ELONGATED INTO THE MIDWEST THAN THE NAM WHICH IS MORE IN LINE WITH THE GFS/GEFS. THE 12Z UKMET REMAINS WELL DISPLACED FROM THE REST OF THE GUIDANCE SUITE. WILL CONTINUE TO FAVOR A 12Z GFS/ECMWF BLEND AT BELOW AVERAGE CONFIDENCE. SHORTWAVE CROSSING TX SUN/MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-GFS BLEND CONFIDENCE: AVERAGE MODEL AGREEMENT IS FAIRLY STRONG WITH THE WAVE MOVING ACROSS NW MEXICO...EVENTUALLY EJECTING INTO THE SOUTHERN PLAINS/TX SUN... THE ONLY SIGNIFICANT DIFFERENCE/STAND OUT IS THE 12Z GFS THAT IS A BIT SLOWER (SEEN BEST AT 7H) AND AS SUCH INTERACTS TO DEVELOP DEEPER CONVECTION WEST WHICH FEEDS BACK ON THE MASS FIELDS. THOUGH NOT OUT OF THE REALM OF POSSIBILITY...THE TIMING OF THE WAVE FAVORS THE BETTER FASTER CLUSTERED MODELS. AS SUCH WILL FAVOR A NON-GFS SOLUTION AT AVERAGE CONFIDENCE MAINLY OVER TX AS FURTHER NORTH THERE IS MUCH STRONGER AGREEMENT TO SUPPORT A OVERALL BLEND THERE SUN/MON. 19Z UPDATE: THE 12Z CMC IS A BIT MORE AMPLIFIED BUT REMAINS IN LINE IN TIMING WITH THE NAM AND 12Z ECMWF/UKMET TO KEEP INITIAL NON-GFS PREFERENCE AT AVERAGE CONFIDENCE. CLOSED MID LEVEL LOW TRACKING FROM THE PACIFIC NORTHWEST SAT TO THE FOUR CORNERS BY TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/ECMWF BLEND CONFIDENCE: ABOVE AVERAGE OVERALL AGREEMENT IS FAIRLY TIGHT GIVEN THE COMPLEXITIES ACROSS THE TERRAIN IN THE WEST. THE ONLY MAJOR DIFFERENCE SEEN IS IN THE OVERALL SHAPE OF THE INNER CORE OF THE UPPER LOW/UPPER HIGH (REX) AND ITS INTERACTION TO THE DOWNSTREAM TROF ACROSS THE EASTERN MIDWEST/WESTERN GREAT LAKES...THE 12Z NAM IS PARTICULARLY AGGRESSIVE WITH THE LEAD SHORTWAVE ENERGY EJECTING INTO THE PLAINS MONDAY NIGHT/TUES MORNING WITH A STRONG/CONSOLIDATED FEATURE. THIS IS SUPPORTED BY 00Z CMC/UKMET BUT GIVEN BOTH THOSE MODELS ARE GENERALLY OUT OF PHASE WITH THE DOWNSTREAM FEATURE AND NOT PREFERRED IT IS DIFFICULT TO SUPPORT THIS STRONGER/CONSOLIDATED FEATURE. THE 12Z GFS ALSO HAS THIS SHORTWAVE FEATURE BUT IS MUCH MORE WASHED OUT AND ALONG WITH THE 00Z ECMWF WHICH IS MUCH FLATTER... ELSEWHERE WITHIN THE TROF IN THE INTERMOUNTAIN WEST/SOUTHWEST...THE OVERALL MASS FIELDS APPEAR STRONGLY AGREED UPON WITH SMALL ENSEMBLE SPREAD. AS SUCH GIVEN THE DIFFERENCES ACROSS THE CENTRAL HIGH PLAINS WILL FAVOR A 12Z GFS/00Z ECMWF BLEND TO SUPPORT THE ENSEMBLE MEANS AND DOWNSTREAM MODEL PREFERENCES. CONFIDENCE REMAINS ABOVE AVERAGE FOR THE 12Z GFS/00Z ECMWF BLEND. 19Z UPDATE: THE 12Z ECMWF IS SLIGHTLY SLOWER AND MORE WOUND UP THAN ITS PRIOR RUN IN LINE WITH ITS BIAS...BUT STILL WELL IN LINE WITH THE EARLIER PREFERRED GFS. THE CMC/UKMET BOTH CONTINUE TO SUPPORT THE IDEA OF A STRONGER/CONSOLIDATED LEAD PIECE OF ENERGY INTO THE CENTRAL HIGH PLAINS...THIS ALSO APPEARS TO SUPPORT A SLIGHTLY FASTER/FURTHER EAST ORIENTATION OF THE TROF BY THE END OF DAY 3 COMPARED TO THE ENSEMBLE MEANS AND GFS/ECMWF. AS SUCH WILL CONTINUE TO SUPPORT A 12Z GFS/ECMWF BLEND AT ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA