MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 234 AM EDT SAT JUN 25 2016 VALID JUN 25/0000 UTC THRU JUN 28/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ AMPLIFYING TROF OFF MID-ATLANTIC COAST CUTS-OFF SUN AND RETROGRADES TOWARD NEW ENGLAND TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/NAM/CMC BLEND CONFIDENCE: AVERAGE SHORTWAVE ENERGY HAS LEFT THE EAST COAST AND WILL BEGIN TO CARVE OUT A WEAK TROF OFF THE EAST COAST EVENTUALLY DEVELOPING INTO A CUT-OFF LOW WITH AN ASSOCIATED SURFACE WAVE ALONG THE FRONT EAST OF GEORGES BANK BY SAT NIGHT/SUN MORNING. MODELS SHOW GENERAL AGREEMENT WITH THIS SOLUTION UP THIS TIME...THOUGH AS THE CUT-OFF "FEELS" THE APPROACH OF THE DEEPER CYCLONE/TROF TO THE WEST...IT RETROGRADES TOWARD THE COAST. THE 12Z ECWMF IS A BIT DEEPER AND DESCENDS SOUTHWARD A BIT MORE THAN THE REST OF THE GUIDANCE SUITE REMAINING LEAST AFFECTED/ABSORBED INTO THE APPROACHING TROF. THE 12Z UKMET IS ON THE OPPOSITE SIDE OF THE SPECTRUM LIFTING DUE NORTH THAN WESTWARD TOWARD NOVA SCOTIA. THE ENSEMBLES GENERALLY SUPPORT THEIR OPERATIONAL SOLUTIONS (MINUS THE SREF...WHICH IS WELL SOUTH EVEN OF THE ECMWF). HOWEVER WILL FAVOR THE MIDDLE GROUND OF THE 00Z GFS/18Z GEFS/12Z CMC AND 00Z NAM. RUN TO RUN VARIATIONS WITH WEAK SYSTEM DOES NOT PROVIDE MUCH CONFIDENCE OVERALL BUT CLUSTERING IS WELL ENOUGH FOR GFS/NAM/CMC BLEND AT AVERAGE CONFIDENCE. 07Z UPDATE: LITTLE CHANGE WITH RESPECT TO THE UKMET OR ECMWF...BOTH ARE ON NE AND SW PORTIONS OF THE SPREAD. THE 00Z CMC DID TREND A BIT DEEPER AND FURTHER SOUTH BETWEEN THE GFS AND ECMWF BUT UNLIKE THE ECMWF...IT EVENTUALLY IS REABSORBED INTO THE FLOW BY TUESDAY MUCH LIKE THE GFS AND AS SUCH WILL KEEP A 00Z NAM/GFS/CMC BLEND AS PREFERENCE. COMPACT UPPER LOW PUSHING ACROSS THE NORTHERN ROCKIES SATURDAY MORNING AND ASSOCIATED DEEP SFC CYCLONE IN S CANADA...BEFORE OPENING UP INTO TROF OVER GREAT LAKES TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: AVERAGE DETERMINISTIC MODELS SHOW SOME SLIGHT WOBBLES AND VARIATIONS INTERMITTENTLY THROUGHOUT THE EVOLUTION OF THE SYSTEM. THE 12Z ECMWF/CMC LAGGING A BIT SUN MORNING OR THE 00Z NAM BECOMING A BIT FASTER TOWARD DAY 3. THE 00Z GFS MAY BE MOST DRAMATIC IN DISPLAYING THIS WOBBLE SUNDAY ACROSS S CANADA DUE TO INTERNAL INTERACTIONS WITH VORT CENTERS BUT RESETS ITSELF TOWARD THE GEFS MEAN AND THE REST OF THE SUITE BY MONDAY AFTERNOON. AN OVERALL OPERATIONAL MODEL BLEND WILL WASH MANY OF THESE INTERNAL INTERACTION/WOBBLES OUT TOWARD VERY STRONG/TIGHT AGREEMENT WITH THE ENSEMBLE MEANS. CONFIDENCE IS SLIGHTLY ABOVE AVERAGE IN THE OVERALL PATTERN/TIMING BUT THE INTERNAL FINER DETAILS THAT MAY RESULT IN HIGHER IMPACT ARE A BIT TOO ELUSIVE TO BE FULLY CONFIDENT IN PREFERRING ONE SOLUTION OR ONE RUN OVER AN OTHER AT THIS TIME. 07Z UPDATE: THE 00Z ECMWF TRENDED A DEEPER S/W CROSSING THE SOUTHERN CANADIAN PRAIRIES RESULTING IN THE BASE OF THE TROF ACROSS THE WESTERN GREAT LAKES (AS THE UPPER LOW UNFOLDS INTO A TROF) TO LAG THE MAIN SUITE MAINLY THRU THE 5-7H LEVELS. THIS SLOWING WAS GENERALLY SUPPORTED BY THE 00Z CMC AND GFS COMPARED TO A FASTER NAM/UKMET AND SPREAD BUT NOT RESULTING IN SIGNIFICANT IMPACT TO SENSIBLE/SURFACE WX ENOUGH TO BREAK FROM INITIAL PREFERENCE OF AN OPERATIONAL MODEL BLEND. CONFIDENCE IS REDUCED A BIT GIVEN THIS INCREASED SPREAD TO AVERAGE THOUGH. TUTT LIFTING ACROSS THE RIO GRANDE RIVER VALLEY BEFORE WEAKENING INTO THE RIDGE TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE LARGE TUTT SEEN IN COAHUILA WILL CONTINUE TO LIFT NORTH AND BREAK DOWN THE RIDGE THROUGH SUNDAY...SLOWLY STALLING AND ALSO WEAKENING. THE 00Z NAM/GFS AND 12Z ECMWF CONTINUE TO RESOLVE A STRONGER SOLUTION THAN THE 12Z UKMET/CMC BUT PLACEMENT/TIMING SEEM WELL ENOUGH TO SUPPORT AN OPERATIONAL MODEL BLEND THROUGH SUNDAY. AT THIS POINT THE TUTT SEEMS TO WEAKEN AND SHEAR OUT SOUTH OF THE REDEVELOPING WESTERN RIDGE OVER THE DESERT SW. LOW AMPLITUDE SHORTWAVE ENTERING NW PACIFIC LATE MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NCEP MODEL BLEND CONFIDENCE: AVERAGE A LOW AMPLITUDE SHORTWAVE APPROACHES THE PACIFIC NORTHWEST SUNDAY UNDER WEAK SWLY FLOW. THE NCEP MODELS ARE A BIT MORE ROBUST WITH THE WAVE INITIALLY LEADING TO FASTER APPROACH. THE 00Z NAM REMAINS FASTEST BUT ALSO MOST AMPLIFIED WHILE THE 00Z GFS IS A BIT MORE ELONGATED WITH A SECONDARY CENTER FURTHER WEST PUTTING IT OUT OF PHASE WITH THE SUITE AS WELL. THE NON-NCEP MODELS ARE IN FAIRLY STRONG AGREEMENT BRINGING THE WAVE INTO THE WEST BY MONDAY AND TRANSLATING IT TO THE APEX OF THE DEVELOPING RIDGE IN THE NORTHERN ROCKIES BY TUESDAY. ALL IN ALL THE ENSEMBLE GRAVITATE TO THE MIDDLE GROUND OF THE NON-NCEP MODELS VERSUS THE FASTER/STRONGER NAM. THE OVERALL AFFECTS OF THIS WAVE ARE QUITE MINIMAL GIVEN IT IS GENERALLY DRY WITH SENSIBLE WX DIFFERENCES MAINLY ALOFT OR HAVE LIMITED LOW LEVEL EFFECTS. AT LEAST UNTIL LATER IN THE FORECAST PERIOD TOWARD WED/THURS. ALL CONSIDERED WILL DEFAULT TO A NON-NCEP BLEND AT THIS TIME SHOULD SUFFICE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA