MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1225 AM EDT FRI SEP 02 2016 VALID SEP 02/0000 UTC THRU SEP 05/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z FINAL 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 HURRICANE HERMINE IS CURRENTLY MAKING LANDFALL IN THE EASTERN FL PANHANDLE AND IS FORECAST TO TRACK NORTHEAST THROUGH THE SOUTHEAST AND EMERGE FROM THE OUTER BANKS SAT MORNING. THE 18Z GFS ALONG WITH THE 18Z GEFS/12Z ECENS MEAN MATCH THE OFFICIAL NHC FORECAST TRACK MOST CONSISTENTLY THROUGH THE SHORT TERM FORECAST. MODEL SPREAD INCREASES WITH TIME MAINLY STARTING SATURDAY DUE TO VARYING DEGREES OF BINARY INTERACTION WITH THE DIGGING SHORTWAVE ENERGY ACROSS THE WESTERN GREAT LAKES THAT DESCENDS INTO THE OH/TN RIVER VALLEY. THERE IS A BIT OF A TREND TOWARD ALLOWING THE MAIN NORTHERN STREAM TROF TO PASS WELL TO THE NORTH AND INCREASE THE SPACING BETWEEN THE WEAKER ENERGY IN THE OH/TN VALLEY AND THE ROBUST INNER CORE OF HERMINE. THIS HAS REDUCED THE INTERACTION...FAVORING THE HERMINE CIRCULATION...AS SUCH TRENDS ARE A SHADE EAST AND FURTHER OFFSHORE OF THE MID-ATLANTIC COAST BY SUN INTO MON. THERE WILL BE A WOBBLE AND EXTRATROPICAL TRANSITION IN THIS TIME PERIOD BUT ITS MAGNITUDE/SIZE OF WOBBLE HAS YET TO MANIFEST CONSISTENTLY FOR HIGH CONFIDENCE. THE 00Z NAM DRAMATICALLY SHIFTED FASTER AND FURTHER EAST THOUGH NOT AS GREAT AS THE 12Z UKMET... IT IS IN THIS VEIN THOUGH IS SOUTH OF THE MAIN CLUSTER. THE 12Z ECMWF SHOWS THE GREATEST INTERACTION AND IS MUCH FURTHER WEST EVEN COMPARED TO ITS 12Z ECENS SUITE...REDUCING CONFIDENCE IN ITS SOLUTION. THE 00Z GFS ALSO DEPICTED EAST AND SOUTH TREND SEEN IN THE NAM. PLEASE REFER TO WPC QPFPFD FOR ADDITIONAL QPF DETAILS ON SOME OF THE RAINFALL TRENDS. FIRST UPPER LOW/TROUGH DIGGING SOUTH OFFSHORE BRITISH COLUMBIA WITH HEIGHT FALLS ADVANCING ACROSS THE NORTHWEST THROUGH FRIDAY AND CENTRAL CANADA BY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: ABOVE AVERAGE MODELS REMAIN IN GOOD ALIGNMENT WITH THE EVOLUTION OF THE UPPER LOW MOVING ACROSS THE NORTHWEST FRIDAY AND AS IT SHIFTS INTO CANADA BY SAT. SPREAD EXISTS INTO SUNDAY AS THE CYCLONE DEVOLVES/SHEARS BUT THAT IS WELL ENOUGH NORTH TO NOT LEAD TO ISSUES ACROSS THE LOWER 48. THE MODELS DO DIFFER ON TIMING OF WEAK SHORTWAVE DRAWN OUT OF THE CENTRAL AND SOUTHERN GREAT BASIN/CENTRAL ROCKIES IN ADVANCE OF THE BASE OF THE TROF AXIS FRIDAY INTO THE DAKOTAS BY SAT MORNING. THE 00Z NAM IS A BIT TOO ROBUST/CONSOLIDATED WITH THIS WAVE AND IS A BIT SLOWER TO FEEL CONFIDENT IN ITS INCLUSION ACROSS THE NORTHERN GREAT PLAINS. AS SUCH A NON-NAM BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE FOR THE ENTIRE SYSTEM THROUGH SAT. TRAILING SHORTWAVE REINFORCING THE TROUGH OVER THE WEST THIS WEEKEND. HEIGHT FALLS MOVING TOWARDS THE PLAINS SUNDAY WITH CONSOLIDATING SURFACE WAVE IN SD BY MON MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS AND 12Z ECMWF/UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE TRAILING SHORTWAVE SKIMS THE BC COAST THROUGH SAT BEFORE REINFORCING THE TROF OVER THE WESTERN US SUNDAY WITH GENERALLY STRONG AGREEMENT UP UNTIL LATE SAT. BY LATE SUNDAY THE CMC IS LAGGING A BIT MORE WOUND UP-BROAD WITH THE BASE OF THE TROF AND EVENTUALLY EXTENDS DEEP SOUTH INTO THE CENTRAL CA/S NV...MOST OUT OF PHASE IN TIMING WITH REST OF THE GUIDANCE. THE 00Z NAM WHILE IN PHASE IN TIMING...SHOWS SOME OF THE TYPICAL DAY 3 BIAS WITH A VERY CONSOLIDATED/STRONG VORT MAX EJECTING OUT OF THE BASE OF THE TROF ON MON...LEADING TO THE TROF LEANING FORWARD COMPARED TO THE BETTER ALIGNED 00Z GFS AND 12Z ECMWF/UKMET. THIS REMAINING THREE ARE A GOOD REPRESENTATION OF THE ENSEMBLE MEANS...AND THEREFORE ARE THE WPC MODEL PREFERENCE AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. GALLINA www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...