MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1250 AM EDT MON AUG 01 2016 VALID AUG 01/0000 UTC THRU AUG 04/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ LONGWAVE TROF OVER GREAT LAKES NARROWS AND AMPLIFIES ALONG NEW ENGLAND/MID-ATLANTIC BY TUES WITH SURFACE FRONTAL ZONE ALONG 40N SLIPPING SLOWLY SOUTH THROUGH MID-ATLANTIC/CAROLINAS BY WED WITH WEAK SURFACE WAVES SHIFTING OFFSHORE SUN NIGHT AND TUES MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE BROAD LONGWAVE TROF OVER GREAT LAKES BEGINS TO NARROW IN LENGTH UNDER INFLUENCE OF STRONGER STRONGER SUBTROPICAL RIDGE IN NORTHWEST ATLANTIC. THIS IN TURN ALLOWS FOR SOME DEEPENING/CONSOLIDATION OF THE UPPER LOW NEAR NOVA SCOTIA WITH THE 00Z NAM CONTINUING TO FOLLOW ITS BIAS BEING A BIT DEEPER/STRONGER THAN MUCH OF THE GUIDANCE. THE 12Z ECMWF SUPPORTS A STRONGER SOLUTION AS WELL BUT ALL IN ALL THERE IS FAIRLY GOOD AGREEMENT THROUGH 03/00Z AS THE TROF AND SURFACE LOWS MOVE OFF SHORE. AFTER THIS TIME THE 12Z CMC STRENGTHENS A LOW ABOUT MID-TROF EAST OF HUDSON CANYON WHICH SUPPORTS A DEEPER/SLOWER SURFACE SOLUTION THAT STANDS OUT COMPARED TO THE REST OF THE SUITE (AS WELL AS BUILDING THESE DIFFERENCES INTO THE SOUTHEAST US COASTLINE). AS SUCH WILL SUPPORT A NON-CMC BLEND AFTER 03/00Z OTHERWISE CONFIDENCE IS SLIGHTLY ABOVE AVERAGE. CLOSED LOW CROSS SW/CENTRAL CANADA SHEARING NW-SE NEAR HUDSON BAY WITH STRONG SURFACE REFLECTION IN CANADA WITH A DRAPED COLD FRONT CROSSING THE NORTHERN PLAINS MON EVENING INTO GREAT LAKES BY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM AND 12Z ECMWF/CMC BLEND CONFIDENCE: BELOW AVERAGE THE CLOSED LOW CROSSING SW CANADA CONTINUES TO SHIFT EASTWARD AND GIVEN HEIGHT FALLS...DRAWS SHORTWAVE ENERGY/SHEAR AXIS OUT OF THE CENTRAL ROCKIES SUPPORTING A SECONDARY SURFACE DEVELOPMENT BY MID-DAY MON OVER W SD. DIFFERENCES IN THE OVERALL EVOLUTION OF THE DEEP LOW AND SHEAR AXIS ARE RELATED TO LOCALITY OF SHORTWAVE ENERGY IN THE AXIS AS WELL AS THE TIMING OF THE EVENTUAL FILLING OF THE UPPER LOW. THE 12Z ENSEMBLE SUITE CONTINUES TO SHOW THE GFS/GEFS MEMBERS BEING QUICK TO WEAKEN/SHEAR THE UPPER LOW TOWARD THE EAST. THE 00Z GFS CONTINUES THIS TREND BUT AT A SLIGHTLY SLOW PACE AS WELL AS BEING WEAKEST WITH THE ENERGY OUT OF THE CENTRAL ROCKIES...MAKING IT SUSPECT. THE 12Z ECMWF HAS STABILIZED ACROSS CANADA WITH CONTINUED SUPPORT OF THE 12Z UKMET/CMC AND SOMEWHAT THE 00Z NAM; THE AGREEMENT TO THE ECMWF/ECENS MEAN IS STRONGEST WITH RESPECT TO TIMING/PLACEMENT OF THE FRONT ACROSS THE GREAT LAKES TO CENTRAL PLAINS AS THE FRONT BECOMES LESS DEFINED. THE 12Z UKMET IS SUSPECT ACROSS THE UPPER MIDWEST INTO GREAT LAKES GIVEN HOW STRONG/CONSOLIDATED THE ENERGY FROM THE CENTRAL ROCKIES CONTINUES TO BE....MAKING IT SUSPECT AS WELL. THE 12Z CMC DOES SUPPORT THE ECMWF SOLUTION FOR THE MOST PART. THE 00Z NAM SEEMS TO BE A MIDDLE GROUND BETWEEN THE GFS/ECMWF AND AS A HEDGE WILL INCLUDE THE NAM TO THE BLEND TO SUPPORT THE IDEA THE ECMWF MAY BE A BIT SLOW/WOUND UP TOWARD ITS KNOWN BIAS. AS SUCH A BLEND OF THE 00Z NAM ALONG WITH THE 12Z ECMWF/CMC IS PREFERRED BUT GIVEN LARGE SPREAD AND SMALL BUT IMPORTANT MOVING PARTS CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE. SECOND CLOSED LOW ENTERING WA BY MON AND ACCELERATING ACROSS N ROCKIES INTO NORTHERN TIER BY THURS...WITH LEE CYCLOGENESIS IN MT WED MORNING TRACKING ACROSS N PLAINS BY THURS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE ON THE HEELS OF THE INITIAL CLOSED LOW BARRELING THROUGH WESTERN/CENTRAL CANADA...ANOTHER DEEP CLOSED SYSTEM SWINGS INTO THE PACIFIC NORTHWEST BY TUESDAY MORNING. OVERALL MODEL AGREEMENT IS DECENT THROUGHOUT THE PERIOD WITH SOLUTIONS GENERALLY STAYING WITHIN THE ENSEMBLE SPREAD. HOWEVER...BY THURS THE 12Z CMC/UKMET ALREADY A BECOMING A BIT MORE PROGRESSIVE AND OPENING UP TO DIGGING HEIGHT FALLS OUT OF NORTHERN CANADA. THE 00Z GFS/NAM ARE A BIT SLOWER TO OPEN AS WELL AS REMAIN SLOWER IN EJECTING THE SURFACE LOW OFF THE TERRAIN IN MT. THE 00Z GFS APPEARS A BIT DEEPER AT THE SURFACE POSSIBLY IN RESPONSE TO HEIGHT/RIDGING DIFFERENCE DOWNSTREAM (SEE SECTION ABOVE). THE ECMWF SPLITS THE DIFFERENCE BETWEEN THE NAM/GFS AND CMC/UKMET...THOUGH MORE TOWARD THE SLOWER NAM/GFS CAMP. AT THIS TIME DIFFERENCES ARE SMALL ENOUGH THAT THE SPREAD ON THURSDAY IS NOT FAVORED IN EITHER DIRECTION BASED ON TRENDS OR DYNAMIC PROCESSES; AS SUCH WILL FAVOR AN OPERATIONAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. INTERACTION/COMBINATION OF SMALL SHORTWAVE TROF OUT OF NORTHERN STREAM AND LINGERING SMALL TUTT CELL OFF CA COAST EVENTUALLY DEEPENING INTO A BROAD TROF ALONG WEST CA COAST BY THURS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS ARE IN FAIRLY STRONG AGREEMENT WITH THE EVOLUTION SETUP OF TWO SHORTWAVE VORT CENTERS THAT DANCE TOGETHER OFF THE CALIFORNIA COAST WED INTO THURS PRESENTING A BROADENING UPPER LEVEL TROF. LOW LEVEL AFFECTS SEEM TO BE MORE LIMITED IN SCOPE WITH RESPECT TO MASS/PRESSURE/WIND FIELDS BUT GIVEN PLACEMENT/TIMING WOULD AFFECT FIRE WX ACROSS THE VICINITY. ONLY THE 12Z CMC IS INITIALLY WEAK WITH BOTH FEATURES WITHIN THE ENSEMBLE SUITE WHICH ALLOWS IT TO DEVELOP FURTHER NORTH AND EVENTUALLY SHIFTS EASTWARD INTO N CA BY THUR...FOLLOWED BY THE GFS THEN UKMET/NAM/ECMWF. ALL CONSIDERING WILL FAVOR A NON-CMC BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. MONSOONAL TUTT CELL AFFECTING SOUTHWEST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS AND 12Z ECMWF/UKMET BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE BROADLY CYCLONIC VORT ENERGY ACROSS NW MEXICO AND AZ CONTINUES TO DEVELOP AND GROW UPSCALE WITH EACH BOUT OF DAILY CONVECTIVE CYCLE GIVEN STAGNANT FLOW. THE 00Z NAM IS QUICK TO GROW UPSCALE BY WED FOLLOWED BY THE UKMET/CMC AND AS SUCH START TO LIFT N AND E TOWARD THE FOUR CORNERS REGION STRINGING OUT UNDER INCREASED SWLY FLOW FROM DIGGING TROF OFF WEST COAST. BY THURSDAY THE FEED BACK APPEARS MUCH TO GREAT FOR THE 00Z NAM WHICH BREAKS FROM THE GENERAL CONSENSUS CLOSING OFF A 588 DM OVER NE NM. THE CMC IS ALSO A BIT FURTHER EAST BUT NOT AS STRONG. OVERALL THE 00Z GFS AND 12Z ECMWF REMAIN WELL AGREED UPON AND REASONABLE GIVEN SETUP...INCLUSION OF THE 12Z UKMET MAY SUPPORT SOME EASTWARD HEDGE. AS SUCH PREFERENCE IS A 00Z GFS AND 12Z ECMWF/UKMET BLEND AT AVERAGE CONFIDENCE. 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