MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 239 AM EDT SAT SEP 03 2016 VALID SEP 03/0000 UTC THRU SEP 06/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TROPICAL CYCLONE HERMINE AND FRONTAL/TROUGH INTERACTION ACROSS THE EAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: PLEASE REFER TO LATEST NHC FORECAST ADVISORY DIFFERENCES REMAIN FAIRLY SMALL IN PLACEMENT OF THE MASS FIELD/CYCLONE LOCATIONS BUT DIFFERENCES IN TIMING AND "SIZE" OF THE WOBBLE/BINARY INTERACTION WITH THE LINGERING WESTERN POTION OF THE EXITING TROF THAT IS NOW SEPARATED OVER THE OHIO VALLEY. THE 12Z ECMWF SUPPORTED BY THE ECENS MEAN CONTINUES TO DEMONSTRATE THE LARGEST WOBBLE WITH THE CLOSEST APPROACH TO THE NJ COAST/HUDSON CANYON IN PART TO A STRONGER REFLECTION OF THE SHORTWAVE IN THE MID-ATLANTIC LATE SAT THROUGH SUN. THE GFS/UKMET ARE NEXT IN ORDER OF STRENGTH OF THE WAVE WHILE THE 12Z CMC/00Z NAM ARE FURTHEST EAST. THE NHC OFFICIAL FORECAST FOLLOWS VERY CLOSELY TO THE 18Z GFS/00Z GFS WHICH HAS BEEN FAIRLY CONSISTENT RUN TO RUN...ALONG WITH SOME INFLUENCE OF THE ECMWF/ECENS MEAN/UKMET...PLEASE SEE WTNT44 (NHC DISCUSSION) FOR ADDITIONAL DETAILS. 07Z UPDATE: THE 00Z UKMET MADE A SHIFT AWAY FROM MODERATE CONSENSUS...AS IT NOW SHIFTS THE CENTER OF HERMINE OUT EAST ALONG THE GULF STREAM GRADIENT BEFORE SWINGING THE LOW BACK TOWARD THE BETTER CLUSTERING IN THE HUDSON CANYON VICINITY. THE 00Z ECMWF SHOWED A SHIFT TOWARD A MORE MODERATE WOBBLE THAN ITS 12Z VERSION BUT STILL MORE DRAMATIC THAN THE 00Z GFS...WHILE THE 00Z CMC SHOWS SIMILAR NOTES BUT A BIT SLOWER AND THEREFORE NORTH AND EAST OF THE OVERALL AVERAGE. LEAD LOW LIFTING OUT OF BC/ALBERTA WITH HEIGHT FALLS ADVANCING ACROSS THE NORTHWEST THROUGH FRIDAY AND CENTRAL CANADA BY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS CONTINUE STRONG ALIGNMENT WITH THE LEAD UPPER LOW ACROSS S BC AS IT LIFTS NE INTO CENTRAL CANADA ALONG WITH SURFACE CYCLOGENESIS WHICH MAINLY AFFECTS AREAS NORTH OF THE US BORDER. THE TIMING/PLACEMENT OF THE ATTENDANT FRONTAL ZONE INTO THE DAKOTAS BY SAT IS AGREED UPON WELL ENOUGH TO SUPPORT GENERAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 07Z UPDATE: LITTLE CHANGES SEEN IN THE NON-NCEP 00Z SUITE TO KEEP A GENERAL MODEL BLEND PREFERENCE. NEXT SHORTWAVE REINFORCING THE TROUGH OVER THE WEST THIS WEEKEND AND LIFTING THROUGH NORTHERN ROCKIES/NORTHERN TIER MON-TUES WITH ASSOCIATED SURFACE WAVE/FRONTAL ZONE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF/UKMET BLEND CONFIDENCE: AVERAGE IN THE WAKE OF THE LEADING WAVE LIFTING OUT BUT PRIOR TO THE NEXT DIGGING SHORTWAVE OUT OF THE PACIFIC STREAM INTO THE MEAN TROF SAT/SUN... A SHORTWAVE EJECTS OUT OF THE CENTRAL ROCKIES WITH A WEAK SURFACE REFLECTION ALONG THE FRONTAL ZONE INTO THE NORTHERN RED RIVER VALLEY BY MONDAY FOLLOWED. WHILE THE FRONTAL ZONE PLACEMENT IS GOOD THE TIMING IS A BIT OFF BETWEEN THE MAIN GLOBAL MODELS AND THE 12Z CMC AND 00Z NAM BOTH ARE A BIT STRONGER WITH THE WAVE A 7H THROUGH THE SURFACE COMPARED TO THE ENSEMBLE SUITE INCLUDING THE CMCE/ECENS MEAN/GEFS. AS THE MAIN WAVE LIFTS THROUGH A SIMILAR TRACK OUT OF THE MEAN TROF ON TUESDAY ACROSS MT/DAKOTAS (WITH SFC WAVE ALONG THE FRONTAL ZONE THROUGH SD/MN); THERE REMAINS MODERATE SPREAD GIVEN THE TIMING/SHAPE/STRENGTH DETAILS. STILL FAIRLY STRONG AGREEMENT IN THE ENSEMBLE SUITE PROVIDE FAIRLY CONSISTENT MEAN SOLUTIONS THAT ARE WELL REPRESENTED BY THE OPERATIONAL 00Z GFS AND 12Z ECMWF ALONG WITH THE 12Z UKMET. GIVEN THIS WILL CONTINUE SUPPORT OF A GFS/UKMET/ECMWF BLEND AT AVERAGE CONFIDENCE. 07Z UPDATE: LITTLE CHANGE IN THE 00Z UKMET/ECMWF OR CMC... AS THE 00Z CMC REMAINS A BIT DEEP (NOTED BEST AT 7H) ACROSS THE RED RIVER VALLEY ON MON MORNING AND THOUGH IT IS BETTER ALIGNED WITH THE MAIN WAVE ON TUESDAY...IT IS A BIT SLOWER OVERALL. THE UKMET SHOWED CLOSER ALIGNMENT TO THE INITIAL PREFERENCE THAT WAS FURTHER BOLSTERED WITH THE 00Z GEFS/ECMWF SOLUTIONS... AS SUCH WILL KEEP THE INITIAL PREFERENCE OF 00Z GFS/UKMET/ECMWF. CONFIDENCE IS A BIT BETTER BUT STILL THERE ARE TOO MANY MOVING PARTS/TIMING ISSUES TO BE HIGHLY CONFIDENCE JUST YET. REMAINING TROF ACROSS THE WEST WITH WEAKER/BROAD WAVE ENERGY ENTERING PACIFIC NORTHWEST TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: AVERAGE THE MEAN GLOBAL TROF CONTINUES TO BE MAINTAIN EVEN AS EMBEDDED SHORTWAVE EJECT OUT OF IT THROUGH TUESDAY ACROSS THE WEST...UNDER FAIRLY STRONG MODEL AGREEMENT. WEAK SHORTWAVE ENERGY IS FORECAST TO BE INJECTED INTO THE NW PORTION OF THE TROF ACROSS BC/WA BY THE END OF THE FORECAST PERIOD. THE 12Z UKMET IS QUITE STRONG WITH THIS WAVE ENERGY INCLUDING A DEEP SURFACE REFLECTION...WHICH SEEMS A BIT TOO AGGRESSIVE GIVEN ENSEMBLE CLUSTER OVERALL; THOUGH THE 00Z NAM HAS TRENDED TOWARD A DEEPER SOLUTION AS WELL THE 00Z GFS REMAINS GENERALLY FLAT IN LINE WITH PRIOR RUNS AS WELL THE 12Z ECMWF/ECENS MEAN. GIVEN THE NAM IS NOT TOO DRAMATIC WITH ITS DEPTH...WILL RETAIN IT IN THE PREFERRED BLEND. AS SUCH A NON-UKMET BLEND IS PREFERRED AT THIS TIME AT AVERAGE CONFIDENCE FOR THE REMAINING WESTERN TROF AND THIS EMBEDDED NW SHORTWAVE ON TUES. 07Z UPDATE: ISSUES SEEN WITH THE 12Z UKMET HAVE TEMPERED TOWARD A FLATTER SOLUTION CLOSER TO INITIAL PREFERENCE MORE IN LINE WITH THE STRENGTH OF THE 00Z NAM. WITH LITTLE CHANGE FROM THE 00Z ECMWF/CMC WILL SUPPORT A GENERAL MODEL BLEND FOR THE TROF. GIVEN THE OVERALL WEAK FEATURES THAT ARE LIKELY TO SHOW RUN TO RUN VARIABILITY FOR THE GLOBAL TROF...CONFIDENCE REMAINS AVERAGE IN THE OVERALL BLEND. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA