MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 250 AM EDT FRI JUL 29 2016 VALID JUL 29/0000 UTC THRU AUG 01/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TUTT ENERGY LIFTING INTO MID-ATLANTIC/NEW ENGLAND FRI INTO SAT WITH SURFACE LOW DEVELOPING IN VA PIEDMONT AND MOVING ALONG NORTHEAST COAST THROUGH SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE SYNOPTIC SPREAD REMAINS FAIRLY SMALL WITH RESPECT TO THE REMAINING SHORTWAVE ENERGY OF THE OLD TUTT TRANSLATING ACROSS THE MID-ATLANTIC INTO NEW ENGLAND BY FRI EVENING. SOME SPREAD REMAINS WITH RESPECT TO THE SURFACE LOW ALONG THE FRONTAL BOUNDARY BUT GIVEN IT IS GENERALLY WEAK...THIS WOULD BE EXPECTED GIVEN THE FIELD'S RESPONSE TO MESOSCALE CONVECTION...PLEASE REFER TO WPC QPFPFD FOR ADDITIONAL DETAILS ON THE QPF/QPF AXIS. THE 12Z CMC IS THE ONLY SIGNIFICANT OUTLIER BEING FAST (ATYPICAL OF THE CMC) AND DEEP (TYPICAL) MAINLY AT THE SURFACE; ESPECIALLY COMPARED TO GEFS/ECENS MEANS. A NON-CMC BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE. 07Z UPDATE: THE 00Z CMC HAS SHIFTED A BIT SLOWER AND THOUGH REMAINS A BIT FAST THAN THE CLUSTER AFTER 30/12Z...AN OVERALL MODEL BLEND IS SUPPORTED AT ABOVE AVERAGE CONFIDENCE. MULTIPLE WEAK SHORTWAVES OVERTOPPING SW RIDGE TO CARVE OUT A BROAD/WEAK TROF ACROSS LOWER MISSOURI RIVER VALLEY FRI AND INTO THE SOUTHERN GREAT LAKES/OH RIVER VALLEY BY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND UNTIL 01/00Z...NON-CMC AFTERWARD CONFIDENCE: SLIGHTLY AVERAGE AVERAGE BROAD TROUGHING EXISTS AND WILL CONTINUE TO DEVELOP ACROSS THE NORTHERN PLAINS INTO THE MS RIVER VALLEY IN THE WAKE OF THE EXITING CLOSED LOW IN CANADA/TUTT CELL LIFTING NORTHEAST THROUGH NEW ENGLAND. THIS PATTERN SUPPORTS NUMEROUS CONVECTIVELY INDUCED UPSCALE GROWTH SCENARIOS...SOME WITH ADDITIVE EFFECTS...AS WAVES DROP SOUTHEAST AROUND THE PERIPHERY OF THE SOUTHWESTERN U.S. RIDGE. THE 12Z CMC AND UKMET BOTH SUPPORT THIS ADDITIVE EFFECT ACROSS THE LOWER OHIO VALLEY INTO LOWER GREAT LAKES BY SAT; THE UKMET LESSER SO. CONTRARY TO THIS THE 12Z ECMWF AND 00Z NAM/GFS CONTINUE TO BE ALIGNED QUITE WELL WITH THE TIMING OF THE ENSEMBLE. THOUGH VARIATION IN QPF CAN BE QUITE SUBSTANTIAL...PLEASE REFER TO QPFPFD FOR ADDITIONAL DETAILS. OTHERWISE WILL CONTINUE TO SUPPORT A 00Z GFS/NAM AND 12Z ECMWF BLEND AS MOST PROBABLE OUTCOME AT THIS TIME. 07Z UPDATE: WHILE THE 00Z UKMET AND CMC CONTINUE TO BE ON THE STRONGER SIDE OF THE GUIDANCE IN CONSOLIDATING THE VORT CENTER IN THE LOWER GREAT LAKES BY SUN BOTH ARE IN BETTER SUPPORT OF EARLIER 00Z GFS/NAM AND ECMWF PREFERENCE. AT THIS POINT THE 00Z CMC SUPPORTS A DEEPER/FURTHER SOUTH 7H AND SFC CENTER ACROSS THE CENTRAL APPALACHIANS/MID-ATLANTIC ON MON. AN OPERATIONAL MODEL BLEND THROUGH 01/00Z AND NON-CMC AFTERWARD IS SUPPORTED AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. LEAD SHORTWAVE TROF CLOSING OFF WHILE CROSSING SW CANADA BY SAT INTO MON SECOND CLOSED LOW APPROACHING THE PAC NORTHWEST BY MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: AVERAGE A DEVOLVING CLOSED LOW IN THE GULF OF ALASKA IS ELONGATING WITH NUMEROUS INTERNAL SHORTWAVES NOTED. AS THE OVERALL PATTERN SUPPORTS SOUTHEASTWARD TRACKING OF THE ENERGY...THE MODELS ARE IN GENERAL AGREEMENT WITH THE EVENTUAL INTERACTION OF SHORTER WAVE FEATURES CONSOLIDATING INTO TWO MORE CONCENTRIC CLOSED LOW(S) ACROSS WESTERN CANADA AND THE GULF OF ALASKA OVER THE WEEKEND INTO MON. THE LEAD WAVE HAS STRONGER MODEL AGREEMENT BUT THERE REMAINS SOME SPREAD PARTICULARLY WITH THE OVERALL STRENGTH. THE 00Z NAM (ALONG WITH THE 12Z UKMET) HAS SHIFTED TO A MUCH DEEPER CONCENTRIC SOLUTION BUT ALSO A NORTHERN SOLUTION WITH THE CENTER/TRACK. THE GFS HAS BEEN VERY SOLID AND CONSISTENT OVER THE PAST DAY OR SO WITH THE EVOLUTION OF THIS LOW THOUGH ALSO ON THE WEAKER/SHALLOWER SIDE IS MORE CENTRAL TO THE OVERALL CLUSTER AND CONTINUES TO BE MOST FAVORED. THE ECMWF HAS BEEN LESS RELIABLE THOUGH APPEARS TO BE CONSOLIDATING ON A SOLUTION...THOUGH THE 12Z RUN (SUPPORTED BY THE 12Z ECENS MEAN) REMAINS THE SOUTHERN-MOST ON THE TRACK OF THE LOW. THE 12Z CMC IS MOST OF AN OUTLIER AS IT REMAINS QUITE ELONGATED/ECCENTRIC COMPARED TO THE OTHER CONCENTRIC DETERMINISTIC MODELS. OVERALL WILL CONTINUE TO FAVOR A NON-CMC BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. THE UPSTREAM SECOND CLOSED LOW APPROACHES VANCOUVER ISLAND/NW WASHINGTON BY THE END OF THE FORECAST PERIOD... MODELS ARE MUCH TIGHTER PACKED ON THE EVOLUTION EXCEPT THE CMC WHICH IS WEAKER/SLOWER. THE 12Z UKMET IS A BIT FAST...PER USUAL BUT NOT ENOUGH TO BREAK FROM THE NON-CMC BLEND FOR BOTH SYSTEMS. 07Z UPDATE: FOR THE LEAD LOW IN SW CANADA SUN/MON: THE 00Z CMC SHIFTED INTO BETTER SUPPORT OF THE 00Z GFS AS WELL AS THE ECMWF THOUGH IT DOES REMAIN THE SOUTHERN SOLUTION TO THE GUIDANCE. THE UKMET WHICH HAD SUPPORTED INCLUSION OF NAM BEING A BIT STRONGER AND NORTH...THE 00Z UKMET BACKED OFF AND THOUGH STILL NORTH IS WEAKER AND MORE IN LINE WITH THE 00Z GEFS; JUST A BIT NORTH OF THE 00Z GFS. THIS MAKES THE NAM AN OUTLIER IN BOTH LATITUDE/TRACK AS WELL AS INTENSITY WITH THIS LEAD WAVE...THOUGH THE NAM IS VERY SOLID WITH THE SECOND WAVE APPROACHING WA BY MON. HOWEVER...THE UKMET IS NOW SLOWER AND MORE ELONGATED WITH THE SECOND WAVE...OTHERWISE THE 00Z ECMWF/CMC ARE ALSO WELL CLUSTERED HERE TOO. ALL CONSIDERED A NON-NAM FOR THE LEAD WAVE AND A NON-UKMET BLEND FOR THE SECOND MAY BE BEST SOLUTION IF CAPABLE; OTHERWISE THE SPREAD AND MODEL DIFFERENCES ARE SMALL ENOUGH TO SUPPORT AN OPERATIONAL MODEL BLEND THOUGH AT SLIGHTLY LOWER CONFIDENCE (AVERAGE) GIVEN THE BROADER SOLUTION THAT EXISTS AFTER BLENDING GALLINA www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...