MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 238 PM EDT FRI JUL 15 2016 VALID JUL 15/1200 UTC THRU JUL 19/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ MID-UPPER ACROSS THE GREAT LAKES...OH VALLEY AND NORTHEAST FRI TO SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM HAS COME INTO BETTER AGREEMENT WITH THE TIMING/PLACEMENT OF THE LAST REMAINING SHORTWAVE TO THE BROADER LARGE SCALE TROF THAT DEVOLVES ACROSS SE CANADA/NORTHEAST US THROUGH SUN MORNING. THIS LEAVES THE 00Z CMC AS THE ONLY MAIN OUTLIER AS IT FAVORS A SLIGHTLY SLOWER...MORE AMPLIFIED AND THEREFORE SOUTHERN TRACK FOR THE SHORTWAVE. THIS GENERATES THE WEAK COASTAL SURFACE WAVE FURTHER OFFSHORE FROM THE FRONTAL ZONE ON SUNDAY AS WELL. THE 00Z CMCE EVEN FAVORS THE REST OF THE GUIDANCE SUITE THAN ITS OPERATIONAL MEMBER. AS SUCH WILL FAVOR A NON-CMC BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z CMC DRAMATICALLY CHANGED FROM BEING SLOW AND MOST AMPLIFIED FLIPPING TO THE OTHER SIDE OF THE SPREAD...WEAKER THOUGH MUCH BETTER TIMED; THOUGH THE DIFFERENCE IS SMALL ENOUGH NOW WITHIN THE ENSEMBLE SPREAD TO SUPPORT AN OPERATIONAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE. DIGGING CANADIAN TROF ALONG WITH S/W ENERGY OUT OF WESTERN TROF SUN ACROSS N TIER WITH FRONTAL PASSAGE ACROSS THE NORTHERN PLAINS/UPPER MIDWEST/GREAT LAKES SUN-MON EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: AVERAGE THERE IS LARGE SPREAD IN THE MODEL GUIDANCE WITH RESPECT TO THE STRONG UPPER LEVEL LOW/TROF DIGGING OUT OF N CANADA SUN INTO EARLY NEXT WEEK THOUGH THE BULK OF THE SPREAD REMAINS NORTH OF THE BORDER WITH CLIPPING EFFECTS (MAINLY IN PLACEMENT OF THE FRONTAL ZONE) ACROSS THE LOWER GREAT LAKES MONDAY. BETTER AGREEMENT EXISTS WITH THE SUBTLE SHORTWAVE EJECTING OUT OF THE CLOSED LOW IN THE NORTHERN ROCKIES IN ADVANCE OF THE DEEPER TROF SUN IN THE DAKOTAS... AND MONDAY INTO THE GREAT LAKES. THE 12Z GFS/NAM CONTINUE TO BE STRONGER WITH THIS SUBTLE WAVE AND DUE TO A MORE AMPLIFIED BUT WEAKER/NARROW TROF OUT OF CANADA ARE A BIT FASTER THAN THE VERY SLOW 00Z ECMWF. AS THE MAIN TROF DIGS...THE 00Z UKMET/CMC FAVOR THE GFS/NAM MORE THAN THE ECMWF BUT THEY HAVE PLACEMENT/SPEED ISSUES. THE UKMET IS A BIT DEEPER/SOUTH AND UNCHARACTERISTICALLY THE CMC IS QUITE FAST EVEN SIGNIFICANTLY OUTPACING THE CMCE. THE 00Z ECMWF IS SUPPORTED BY THE 00Z ECENS BUT THERE IS QUITE A LARGE AMOUNT OF SPREAD EVEN WITHIN THE MEMBERS AT THIS TIME PERIOD TO REDUCE SOME CONFIDENCE IN THE SOLUTION. THE LAST 2 CYCLES OF THE OPERATIONAL EC ARE MUCH FURTHER SOUTH WITH THE INNER CORE OF THE UPPER LOW AND THAT LEADS TO A STALLING OF THE FRONTAL ZONE ACROSS THE NORTHERN TIER OF US. WHEN THE ECMWF SHOWS BIAS/ERROR...THIS APPEARS TO BE THE TYPICAL SETUP; SLOW AND TOO WOUND UP. THE 12Z GFS EVEN APPEARS A BIT FAST COMPARED TO THE GEFS THOUGH LESSER SO THAN THE ECMWF/ECENS SPREAD; THOUGH THIS APPEARS TO HINT AT THE TYPICAL FAST GFS BIAS BY DAY 3 AS WELL. THE 12Z NAM APPEARS A NICE MIDDLE GROUND IN PLACEMENT BUT ALSO SHOWS ITS BIAS A BIT WITH DEEPER/STRONGER FEATURES PARTICULARLY BY DAY 3. WILL FAVOR A 12Z GFS/NAM AND 00Z ECMWF BLEND THOUGH WEIGHTED ONLY 1/4 TOWARD THE SLOWER EC AND BETTER REPRESENT THE ECENS MEAN (USE THE 00Z ECENS IN A BLEND IF AVAILABLE IN LIEU OF 00Z ECMWF RUN IF POSSIBLE). THOUGH SPREAD IS HIGH...THE LOCATION DIFFERENCES ARE FAIRLY SMALL DUE TO THE FRONTAL ZONE/TROF FLATTENING E-W ACROSS THE GREAT LAKES; CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE. 19Z UPDATE: ALL 12Z NON-NCEP SUITE TRENDED TOWARD THE 12Z GFS SOLUTION PRESENTING A MUCH REDUCED SPREAD WITH RESPECT TO THE STRONG CANADIAN TROF...MOST SO ON THE SOUTHERN PERIPHERY OF THE SYSTEM WHICH TRACKS ACROSS THE NORTHERN TIER INTO THE GREAT LAKES. MOST DRAMATIC WAS THE 12Z ECMWF REDUCING ITS DEEP/SLOW UPPER LOW...ALLOWING FOR A FASTER NARROWER TROF AND THOUGH STILL SLOWER THAN THE REST OF THE GUIDANCE IS MORE IN LINE WITH THE OVERALL PREFERENCE. THE 12Z UKMET REDUCED ITS STRONGER SOUTHERN SOLUTION...AND THE CMC SLOWED SIGNIFICANTLY...THOUGH BOTH STILL ARE A BIT STRONGER SOUTH DEVELOPING A SURFACE WAVE ACROSS ONTARIO. THE TIMING/STRENGTH OF THE FRONT ACROSS THE US IS MUCH BETTER AS WELL ENOUGH SO TO SUPPORT AN OPERATIONAL MODEL BLEND. THOUGH SPREAD REMAINS MODERATE...THE CONFIDENCE IS INCREASED TO AVERAGE TO SLIGHTLY ABOVE AVERAGE IN THIS COMPROMISE. CLOSED LOW ALONG WA/BC BORDER WILL DRIFT TOWARD THE NORTHERN ROCKIES AND STALL THROUGH SAT NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND UP TO 17/00Z NON-UKMET BLEND THEREAFTER CONFIDENCE: ABOVE AVERAGE UP TO 17/00Z...AVERAGE THEREAFTER MODELS CONTINUE TO BE FAIRLY TIGHT AGREEMENT IN PLACEMENT/STRENGTH AND TIMING AS THE CLOSED LOW OVER BC/WA BORDER SHIFTS EAST TO CB/ALB/MT/ID VICINITY AND STALLS THROUGH 17/00Z...ENOUGH TO SUPPORT AN OPERATIONAL BLEND AT ABOVE AVERAGE CONFIDENCE UP TO THAT POINT. SUN/MON: MODELS RAPIDLY DIVERGE AS THE WAVE IS AT THE APEX OF THE STEERING FLOW/AMPLIFYING RIDGE. THE 00Z UKMET/CMC BOTH SHIFT THE ENERGY BACK NORTHWEST INTO THE DEVELOPING CLOSED LOW ACROSS THE PACIFIC NORTHWEST. COUNTER TO THIS THE 12Z NAM/GFS CONTINUE THE TREND SEEN IN THE 00Z RUNS AND ECMWF OF DRAWING IT EAST OF THE RIDGE WITH LARGE SPREAD IN SPEED/TIMING GIVEN INFLUENCE OF THE DIGGING TROF OUT OF CENTRAL CANADA. THE 12Z NAM IS FASTEST WITH THE ACCELERATION EAST AND ACTUALLY PHASES IT WITH THE DIGGING TROF...INTO THE WESTERN GREAT LAKES BY MONDAY EVENING. THE 00Z ECMWF FOLLOWS BUT AT A MUCH SLOWER PACE INTO THE UPPER MS VALLEY/W WI BY THE SAME TIME PERIOD. THE 12Z GFS (HAVING A WEAKER AND FASTER EASTWARD MOVING CANADIAN TROF) IS MUCH SLOWER LEAVING THE WAVE SHEARED OUT OVER N ND. GIVEN THE INFLUENCES OF THE TROF ARE MORE IMPORTANT AFTER THIS POINT AND SENSIBLE WX DIFFERENCES SEEM MINOR IN THE GRANDER SCHEME... THINKING A BLEND OF THE NAM/GFS AND ECMWF MAY SUFFICE FOR THIS WAVE AFTER 17/00Z AT AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z CMC HAS BEGUN TO CONFORM WITH THE IDEA OF SHIFTING THE WEAKENING WAVE EAST OF THE RIDGE...EVENTUALLY BECOMING SHEARED ENOUGH TO BE NON-TRACKABLE BY THE END OF THE PERIOD. ONLY THE 12Z UKMET CONTINUES TO SHIFT A MAJORITY OF THE S/W ENERGY WESTWARD. OVERALL IMPACTS REMAIN MINOR AFTER 17/00Z FOR THIS FEATURE TO SUPPORT A NON-UKMET BLEND AFTER 17/00Z. DEVELOPING CLOSED LOW OFF WA/OR COAST SUN NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE BY SAT NIGHT/SUN MORNING CARVES OUT THE CLOSED LOW OFF THE PACIFIC NORTHWEST COAST. THE 12Z NAM CONTINUES TO INJECT THE SHORTWAVE ENERGY OVER THE TOP OF THE RIDGE SLOWER THAN THE REST OF THE GUIDANCE SUITE...BUT CONTINUES TO TREND FASTER. WHILE THE MASS FIELDS SEEM TO EVENTUALLY MATCH UP JUST OFF THE COAST BY EARLY MONDAY...THE PLACEMENT OF IMPORTANT WX PRODUCING INTERNAL SHORTWAVES BELIE THE MODEL SPREAD/DIFFERENCES IN SOME OF THE SENSIBLE FIELDS SUCH AS QPF. THE 12Z GFS MAY BE A BIT AGGRESSIVE WITH THE HEIGHT PACKING ACROSS THE NORTHWEST STATES LEADING TO STRONGER FIELDS WHILE THE ECMWF MAY BE A TOO AMPLIFIED WITH THE RIDGING OVER THE ROCKIES AN THEREFORE SUPPORT SOME SMALL RETROGRADING LATER MONDAY COMPARED IT THE 00Z ECENS MEAN. THE 00Z UKMET LIKE THE NAM IS A BIT SLOWER IN INJECTING THE STRONGER SHORTWAVE ENERGY THAT EVENTUALLY ELONGATES THE CLOSED LOW SW-NE MAKING IT A BIT LESS FAVORABLE. OVERALL THE ENSEMBLE MEANS ARE THE MOST ALIGNED (SREF/CMCE/ECENS AND GEFS) SHOWING STRONG CONFIDENCE IN THE OVERALL PATTERN. AS SUCH WILL FAVOR A BLEND OF 12Z GFS AND 00Z ECMWF/CMC (AND ANY ENSEMBLE MEAN AVAILABLE TO BLEND) AS PREFERENCE AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: SOME OF THE ISSUES NOTED WITH THE 00Z UKMET/CMC AND ECMWF HAVE RESOLVED THEMSELVES BETTER TO ALIGN MORE WITH THE ENSEMBLE MEANS WHICH CONTINUE TO BE WELL MATCHED WITH THE INCLUSION OF THE 12Z GEFS MEAN. AS SUCH WILL FAVOR A NON-NAM BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA