MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 236 PM EDT SAT JUL 16 2016 VALID JUL 16/1200 UTC THRU JUL 20/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GREAT LAKES...OH VALLEY AND NORTHEAST SAT TO SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: ABOVE AVERAGE ENSEMBLES ARE FAIRLY STRONGLY ALIGNED WITH THE WEAKENING BASE OF THE LARGER SCALE TROF WITH THE LAST EXITING SHORTWAVE CROSSING NEW ENGLAND SUN. THE 12Z NAM CONTINUES A BIT STRONGER/MORE AMPLIFIED THAN THE REST OF THE SUITE EVEN CLOSING OFF A SFC WAVE NEAR ME/NB BY 18/00Z. THE NAM IS NOT TOO FAR OFF THE STRONG CONSENSUS THOUGH WILL REMOVE IT FROM THE PREFERENCE GIVEN THE SPREAD IN THE SREF SUGGESTS THE 12Z OPERATIONAL MAYBE TOO DEEP EVEN FOR ITS ENSEMBLE. AS SUCH A NON-NAM BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z ECMWF/ECMWF BOTH TRENDED A BIT DEEPER TO MATCH THE 12Z GFS... STILL THE NAM APPEARS A BIT DEEPER ALOFT (5-7H) IN THE MASS FIELDS TO FULLY INCORPORATE IT FULLY. CONFIDENCE IS VERY HIGH IN THE OVERALL TIMING/PLACEMENT AND ORIENTATION OF THE FRONTAL ZONE/SHORTWAVE TROF. NORTHERN TO CENTRAL PLAINS/UPPER MIDWEST/GREAT LAKES/NORTHEAST SUN-MON NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE WV LOOP SHOWS SHORTWAVE PACKET EJECTING AROUND THE SE SIDE OF CLOSED LOW CROSSING MT AT THIS TIME; THIS WAVE WILL CONTINUE TO AMPLIFY JUST IN ADVANCE OF STRONG DIGGING CANADIAN TROF. MODELS ARE IN FAIRLY STRONG AGREEMENT IN PLACEMENT/STRENGTH AND TIMING OF THE MT SHORTWAVE CROSSING THE NORTHERN TIER AND HAVE BECOME MUCH BETTER ALIGNED WITH HOW MUCH STRENGTH/AMPLIFICATION SOUTHWARD EXISTS WITH THE CANADIAN TROF. THE GFS WHICH HAD BEEN MOST RELUCTANT TO AMPLIFY SOUTHWARD HAS TRENDED IN THE DIRECTION OF THE MOST AMPLIFIED 00Z ECMWF...THOUGH AS THE COMBINATION OF THE BASE OF THE TROF AND SHORTWAVE FROM MT PROGRESS ACROSS THE GREAT LAKES...THE GFS DOES NOT ROUND/BROAD AND SUPPORT A STRONGER SURFACE REFLECTION ALONG THE FRONTAL ZONE IN S ONTARIO BY SUN NIGHT AND REMAINS SLIGHTLY FASTER THAN THE REST OF THE GUIDANCE. THE 12Z NAM...LIKE THE GFS...IS LESS ROUNDED/BROAD ACROSS THE BASE OF THE TROF AND HINTS AT SOME POTENTIAL SLOW/WOUND UP BIAS OF THE ECMWF/CMC. THE 00Z UKMET IS NEARLY A EQUAL BALANCE OF THE NCEP MODELS AND THE ECMWF/CMC...FURTHER SUGGESTING A COMPROMISE/BLEND. GIVEN THE SPREAD FOR THE FRONTAL ZONE ACROSS THE U.S. DOMAIN IS FAIRLY LOW GIVEN THE GFS SHIFT; PREFERENCE IS FOR AN OPERATIONAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z ECMWF TRENDED A BIT FASTER AND LESS WOUND UP WITH THE INTERACTION BETWEEN THE TWO STREAMS MATCHING CHANGES BY THE 12Z GFS/NAM TOWARD A BETTER AGREEMENT OVERALL. THIS MAY BE BEST REFLECTED AT THE SURFACE WHERE THE SURFACE LOW TRENDED NORTHWARD IN ONTARIO. THIS PROVIDES STRONGER CONFIDENCE AND WITH LITTLE CHANGES IN THE CMC/UKMET...WILL KEEP WITH OPERATIONAL MODEL BLEND AS PREFERENCE. CLOSED LOW ALONG MT/CANADA BORDER DRIFTING EAST AND WEAKENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE WELL DEFINED CLOSED LOW ALONG THE WA/ID/MT/BC BORDER WILL CONTINUE DRIFT/STALL AS IT SLOWLY SPINS DOWN THROUGH SUNDAY EVENING. AFTERWARD ITS IMPACT TO THE OVERALL PATTERN IS VERY MINIMAL BUT THERE IS A VAST DIFFERENCE IN ITS EVOLUTION/TRACK. THE BULK OF GUIDANCE CONTINUES TO DIRECT IT INTO THE WESTERLY FLOW ON THE EAST OF THE AMPLIFYING SURFACE RIDGE. THE STRONGER/MORE CONCENTRIC SOLUTIONS (ECMWF/CMC) ARE A THE FASTEST TO ACCELERATE IT EAST INTO THE WESTERN PORTION OF THE BASE OF TROF IN THE GREAT LAKES. THE 12Z NAM IS CLOSER TO THIS FASTER ECMWF/CMC SOLUTION BUT IS STRETCHED THROUGH SHEARING FORCES TO LAG A BIT MORE THAN THE ECMWF/CMC. THE 12Z UKMET CONTINUES TO SHIFT IT BACK NW INTO THE DEVELOPING CLOSED LOW. THIS WAS SUPPORTED BY THE 12Z GFS WHICH FILLED FASTER THAN THE NAM/ECMWF/CMC AND PRIOR GFS RUNS; AS SUCH IT DRIFTS DUE NORTH AND AMPLIFIES THE RIDGE A BIT FURTHER EAST THAN PRIOR GFS RUNS. THE SENSIBLE WX IMPACT BEING SMALL EVEN WITH LARGE SPREAD WITH THIS WEAK SYSTEM; CONTINUITY WOULD FAVOR THE FASTER/STRONGER MEMBERS AND AS SUCH A BLEND OF THE 12Z NAM AND 00Z ECMWF/CMC IS PREFERRED AFTER 18/12Z WITH AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z CMC/ECMWF BOTH JOINED THE UKMET/GFS AFTER 18/12Z WITH RESPECT TO THE REMAINING WEAK WAVE AND DRIFTS IT NORTHWARD. AT THIS POINT THE IMPORTANT PORTION OF THE REMAINING LIFE-CYCLE OF THE CYCLONE IS WELL HANDLED BY AN OPERATIONAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE. DEVELOPING CLOSED LOW OFF WA/OR COAST SUN NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND UNTIL 19/00Z 12Z GFS/ECMWF BLEND AFTERWARD CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS HAVE COME INTO BETTER CONSENSUS AS THE ENERGY HAS OVER-TOPPED THE PACIFIC RIDGE AND IS DESCENDING TO CARVE OUT A CLOSED LOW ALONG THE WA/OR COAST BY LATE SUN/EARLY MON. THIS CONGRUENCE WITH EACH OTHER AS WELL AS THE ENSEMBLE MEANS CONTINUES THROUGH MUCH OF THE EARLY FORECAST PERIOD UNTIL ABOUT 19/00Z (TUES) WHEN AN INTERNAL SHORTWAVES SUPPORT ELONGATING THE TROF SW-NE. THE 12Z NAM CONTINUES TO BE MUCH ROBUST WITH THE LEADING SHORTWAVE EJECTING OUT OF WA INTO THE ROCKIES...THIS IS FOLLOWED BY THE UKMET AND SREF...WHILE THE 12Z GFS/00Z ECMWF AND CMC AS WELL AS THE GEFS/CMCE/ECENS MEAN ARE SLOWER AND LESS AMPLIFIED. ALL CONSIDERED AN OPERATIONAL MODEL BLEND MAY WORK PRIOR TO 19/00Z BUT REMOVAL OF THE UKMET/NAM SEEMS PRUDENT GIVEN RUN TO RUN ENSEMBLE TRENDS AND STRONG AGREEMENT OF THE REMAINING DETERMINISTIC RUNS; THEREFORE AFTER 19/00Z A 12Z GFS AND 00Z ECMWF/CMC BLEND IS PREFERRED AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z UKMET CONTINUES TO MATCH THE 12Z NAM BEING A BIT MORE ELONGATED OVERALL THOUGH MORE SO ACROSS THE WESTERN PORTION OF THE TROF. THE 12Z CMC HOWEVER REMAINS MOST CONSOLIDATED AND SLOW IN EVOLUTION AMPLIFYING THE RIDGE ACROSS THE N ROCKIES INSTEAD OF SHEDDING THE LEAD SHORTWAVE OUT OF WA INTO S CANADA LIKE THE REST OF THE DETERMINISTIC GUIDANCE. THE 12Z ECMWF ALSO TRENDED A BIT FASTER LIKE THE 12Z GFS THOUGH A SHADE SLOWER TYPICAL OF THE PAIR. THE 12Z GEFS SUPPORTS THIS FLATTENING OF THE RIDGE IN THE N ROCKIES AS WELL. AS SUCH AFTER 19/00Z WILL SUPPORT AN 12Z GFS/ECMWF BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA