MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1228 AM EDT TUE SEP 06 2016 VALID SEP 06/0000 UTC THRU SEP 09/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ POST-TROPICAL CYCLONE HERMINE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: PLEASE REFER TO NHC DISCUSSION 00Z GFS AND 12Z ECMWF/CMC AFTER 08/12Z CONFIDENCE AFTER 08/12Z: AVERAGE WELL DEFINED LOW LEVEL CIRCULATION REMAINS UNDER A BROADER UPPER LEVEL PATTERN WITH SYNOPTIC TROF/SHORTWAVE LEADING TO ELONGATED 5H PATTERN ALONG THE EAST COAST. MODELS CONTINUE TO BE IN FAIRLY TIGHT AGREEMENT AS THE OVERALL PATTERN DEVOLVES AND WEAKENS. THE 00Z NAM IS ONE OF THE FIRST TO BREAK DOWN AS IT FAVORS THE BROADER UPPER LEVEL PATTERN PARTICULARLY THE SYNOPTIC SHORTWAVE AT THE BASE OF THE CUT-OFF LOW...AS SUCH THIS IT BREAKS FROM BEST ALIGNMENT THURSDAY SUPPORTING THE REMAINING TROF TO REMAIN SOUTH BETWEEN THE SUBTROPICAL RIDGES THAT FLANK IT ON EITHER SIDE. THE REST OF THE SUITE BEGINS TO FILL THE TROF IN PLACE OR SLOWLY ABSORB IT INTO THE NORTHERN STREAM. THE 12Z UKMET IS ON THE OPPOSITE SIDE OF THE SPECTRUM THAN THE 00Z NAM...FAVORING RETAINING THE STRONGER SURFACE REFLECTION AND DEEPER VORTEX ALOFT WITH HERMINE...AND AS SUCH IS INFLUENCED BY THE NORTHERN STREAM EARLIER AND ALSO STARTS TO BREAK FROM OTHERWISE TIGHT CONSENSUS. AS SUCH THE REMAINING 00Z GFS AND 12Z ECMWF/CMC AND THEIR ENSEMBLE MEANS ARE MOST IN LINE WITH THE CURRENT NHC OFFICIAL FORECAST...AND AFTER FORECAST DISSIPATION AT 48/60HRS. SHORTWAVE LIFTING INTO THE NORTHERN HIGH PLAINS INTO CENTRAL CANADA TONIGHT ACCOMPANIED BY SLOW-MOVING FRONTAL ZONE WITH SFC WAVES OF LOW PRESSURE ACROSS MN AND SOUTHEAST ONTARIO ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: MULTI-MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS CONTINUE TO FORECAST A SW-NE ORIENTED FRONTAL ZONE FROM THE CENTRAL HIGH PLAINS NORTHEAST TO THE UPPER MS VALLEY/LAKE SUPERIOR/ONTARIO WITH WAVES OF LOW PRESSURE DEVELOPING DEVELOPING ALONG THE FRONT ACROSS NE MN/LAKE SUPERIOR INTO ONTARIO TODAY. GIVEN THE CONFLUENCE OF THE MAIN WAVE INTO THE SW FLOW ALOFT...THE FRONTAL ZONE IS LOCKED IN PLACE AND THE MODELS HAVE BECOME TIGHTER IN AGREEMENT WITH THE SFC WAVE EVOLUTION TO SUPPORT A GENERAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE. SHORTWAVE CROSSING THE PACIFIC NW AND NORTHERN ROCKIES TUESDAY AND INTO THE NORTHERN PLAINS WED PHASING WITH SOUTHERN STREAM ENERGY OUT OF SOUTHWEST INTO THE GREAT LAKES THURS/NEW ENGLAND FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE SHORTWAVE ENERGY PROGRESSES ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES TUE AND THEN INTO THE NORTHERN PLAINS WED. AS THE WAVE CONTINUES EAST...LOW PRESSURE IN THE CENTRAL PLAINS EJECTS NORTHEAST AND MOVES INTO THE UPPER MS VALLEY LATE WED/WED NIGHT. MODELS DEVELOP DIFFERENCES IN THE STRENGTH OF THIS SURFACE LOW DEPENDENT ON THE STRENGTH OF SHORTWAVE ENERGY LIFTING OUT OF RETURN TROPICAL FLOW OUT OF THE SOUTHWEST AND THE MAGNITUDE OF PHASING. THE 00Z NAM AND GFS SUPPORT A TRACK OF THE NORTHERN STREAM SHORTWAVE A BIT SOUTH OF THE NON-NCEP SUITE RESULTING IN A DEEPER WOUND UP SOLUTION; WHILE THE 00Z NAM IS SLOWER AND THE 00Z GFS IS FASTER...THE TREND OF THE GFS WAS TO SLOW A BIT TOWARD BETTER PHASING TIMING WITH THE ENERGY IN THE RETURN FLOW CLOSER TO THE FLATTER SOLUTION OF THE 12Z ECMWF WHICH BOTH SEEM IN LINE WITH THE OVERALL MEAN. THE 12Z UKMET IS MUCH STRONGER WITH THE WAVE IN THE SOUTHERN STREAM AND AMPLIFIES IT MUCH GREATER THAN THE REST OF THE SUITE IN THE CENTRAL GREAT LAKES INTO SE CANADA; WHILE THE 12Z CMC WAS SIMILAR TO THE ECMWF WAS SLOWER PARTICULARLY OUT OF THE SOUTHERN STREAM. WHILE THERE ARE SOME SIMILARITIES THERE REMAIN ENOUGH DIFFERENCE TO NOT HAVE FULL CONFIDENCE...BUT A BLEND OF THE 00Z GFS ALONG WITH THE 12Z ECMWF SEEMS A MORE CENTRAL COMPROMISE WHILE KEEPING ALIGNED AS REPRESENTATION OF THE ENSEMBLE SUITE. A 00Z GFS/12Z ECMWF BLEND IS PREFERRED BUT AT SLIGHTLY BELOW AVERAGE CONFIDENCE. PACIFIC SHORTWAVE RAPIDLY MOVING INTO BC THURSDAY AND INTO THE NORTHERN HIGH PLAINS FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF/UKMET BLEND CONFIDENCE: BELOW AVERAGE AS THE NEXT PACIFIC WAVE APPROACHES TOWARD BC BY THURSDAY THE OVERALL MEAN TROF THAT HAS DOMINATED THE WEST CONTINUES TO FLATTEN WITH THIS WAVE BRINGING THE END TO IT HAS THE WAVE AMPLIFIES THROUGH THE NORTHERN ROCKIES IN A VERY PROGRESSIVE MANNER. TIMING DIFFERENCES RESULT IN THE ENSEMBLE/GLOBAL GUIDANCE SPREAD...MAINLY DRIVEN BY DOWNSTREAM COMPOUNDING DIFFERENCES. AS A RESULT THE 00Z NAM IS SLOWEST AND DEEPEST THOUGH THE MEAN TROF WHICH SEEMS LESS LIKELY GIVEN THE PATTERN CHANGE/PROGRESSIVE NATURE TO THE FLOW. THE 00Z GFS TRENDED A BIT FASTER AND FLATTER BUT STILL SITS ON THE WESTERN EDGE OF THE GUIDANCE SUITE. THE 12Z ECMWF AND ECENS MEAN WHICH HAVE BEEN MOST CONSISTENT WITH THE PROGRESSIVE NATURE OF THE TROF ARE THE FASTEST WITH THE AXIS NEARING THE NORTHERN RED RIVER BY 12Z FRIDAY; WITH THE 12Z UKMET LAGGING JUST A BIT. THE 00Z CMC IS A MIDDLE GROUND SHOWING SOME AMPLIFICATION (MAINLY AT 7H) NEARING THE TRENDING FASTER 00Z GFS. AS SUCH WILL FAVOR THE MORE PROGRESSIVE 12Z ECMWF/UKMET BLEND BUT CONFIDENCE IS BELOW AVERAGE GIVEN THE PATTERN TRANSITION...THE WAVE IS STILL WELL UPSTREAM OFFSHORE AND DEPENDENCE ON DOWNSTREAM WAVE WHICH HAS LOW CONFIDENCE/VARIATION AT THIS TIME AS WELL. TROPICAL CYCLONE NEWTON MOVING TOWARD BAJA CALIFORNIA AND SW U.S BY THURS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: PLEASE REFER TO NHC DISCUSSION 00Z NAM/GFS AND 12Z ECWMF BLEND AFTER 08/12Z CONFIDENCE AFTER 08/12Z: AVERAGE THERE IS FAIRLY TIGHT CONSENSUS OF THE GLOBAL MODEL SUITE AND ENSEMBLE SUITE WITH EXCEPTION OF THE 12Z UKMET WITH THE OFFICIAL NHC TRACK UP TO LANDFALL NEAR THE SW TIP OF BAJA AT 06/12Z. THE UKMET IS DISPLACED SOUTH AND WEST AND REMAINS SO THROUGH THE REMAINDER OF THE LIFE CYCLE OF NEWTON...THOUGH THIS ALSO MEANS A FURTHER WEST SOLUTION TO AFFECT CENTRAL AZ MORE. THIS IS OPPOSED TO THE BETTER CONSENSUS AFFECTING THE MOUNTAINS OF SONORA INTO SE AZ/SW NM BY THURS. BY THIS TIME THE 12Z CMC IS LAGGING THE TIGHTER CONSENSUS (AS IT IS ALSO BROADER AND WEAKER). AS SUCH USE OF A 00Z NAM/GFS AND 12Z ECMWF WITH ECENS MEAN/GEFS MEAN SHOULD SUFFICE TO MATCH THE NHC FORECAST BEST. GIVEN THE POTENTIAL IMPACT OF RAINFALL PLEASE REFER TO WPC QPFPFD/EXCESSIVE RAINFALL OUTLOOK FOR ADDITIONAL DETAILS/PREFERENCES PERTAINING TO QPF. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA