MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 312 AM EDT WED SEP 23 2015 VALID SEP 23/0000 UTC THRU SEP 26/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. ...RESENT FOR CORRECTION MID-LEVEL SYSTEM IN KS...PREFERRING 00Z RUN OF EC/UK/CMC TROUGH DIGGING OFFSHORE OF THE PACIFIC NORTHWEST RIDGING BUILDING ACROSS THE SOUTHWEST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z ECMWF/GFS AND 21Z SREF CONFIDENCE: AVERAGE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH SIMILARLY SHAPED POSITIVE TILT TROF AND SW-NE ORIENTED SW US RIDGE THROUGH DAY 3 WITH DECREASING ENSEMBLE SPREAD. THE 18Z GEFS IS STILL FORWARD/FASTER WITH THE PROGRESS OF THE TROF COMPARED TO THE ECMWF ENSEMBLES...BUT THOSE HAVE SHIFTED EAST AS WELL WITH TIGHTER PACKING. THE 21Z SREF LOOKS QUITE SIMILAR TO THE 12Z ECENS MEAN WITH GOOD AGREEMENT WITH THE 12Z ECMWF. THE 00Z DETERMINISTIC NAM IS STRONGER/MORE CONSOLIDATED WITH ITS SHORTWAVE FEATURES...WITH A DEEPER S/W ROUNDING THE BASE ON THURS NIGHT...WHICH LAG MUCH OF THE OTHER DETERMINISTIC MODELS...ALSO LEADS TO A COMPOUNDING EFFECT ON THE STRENGTH OF THE LAST WAVE DEEPER OVER VANCOUVER ISLAND AND SLIGHTLY FASTER WITH THE OVERALL TROF ORIENTATION ON DAY 3. THE 18Z GFS BACKED UP BEING A WESTERN MEMBER OF THE GEFS SUITE BECOMING FOLLOWED IN STEP WITH THE 00Z RUN AS WELL MAKING BETTER AGREEMENT WITH 12Z ECMWF AND THE 12Z ECENS MEAN (WHICH SHIFTED EAST TO A STRONGER COMPROMISE). THE 00Z ECMWF AND 00Z UKMET SPED UP A BIT BY THE END OF DAY 3 PARTICULARLY NORTH IN THE TROF BRINGING THE SHORTWAVE INTO VANCOUVER ISLAND ABOUT 3-6HRS EARLIER THAN THE EARLIER PREFERENCE...THOUGH MORE AMPLIFIED THAN THE 00Z NAM. THIS OPENS THE SPREAD A BIT MORE REDUCING CONFIDENCE A BIT. THE 00Z CMC CONTINUED WITH ITS 12Z TREND IN EVOLVING SIMILAR TO THE PREFERRED ORIENTATIONS...BUT REMAINS WEAKER NORTH IN THE TROF AND BROADER/MUCH STRONGER IN THE BASE WHICH IS OUT OF PHASE WITH THE BETTER PACKING/SHAPE OF THE OTHER GUIDANCE. THIS SUPPORTS A BLEND OF THE 00Z ECMWF/UKMET/GFS AND 21Z SREF AT AVERAGE CONFIDENCE. MID-LEVEL SYSTEM DROPPING INTO KS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z ECMWF/UKMET/CMC CONFIDENCE: AVERAGE THE 00Z GFS STILL REMAINS THE OUTLIER IN HANDLING THE REMNANTS OF TROPICAL DEPRESSION 16E...THE LEADING SHORTWAVE REMAINS NORTH OF STRONGER SOUTHERLY CLUSTERING WHICH THEN STALLS AND WEAKLY SHEARS OUT ACROSS THE MIDWEST INTO THE SW GREAT LAKES ON SAT...THOUGH THERE IS BETTER AGREEMENT WITH THE SECONDARY SHORTWAVE CURRENTLY OVER CO...DROPPING IT SE INTO NEW MEXICO/WESTERN PANHANDLE OF TEXAS BY FRIDAY MORNING. THE 00Z NAM IS ALSO A BIT NORTH BUT UNLIKE THE GFS WEAKENS THE FEATURE AND DROPS SOUTH ACROSS KS BY FRIDAY...HOWEVER UNCHARACTERISTICALLY WEAKER THAN THE HIGHLY CLUSTER 12Z ECMWF/CMC/UKMET. THE 12Z ECMWF HAS BEEN PERSISTENT/CONSISTENT OVER THE LAST FEW RUNS WITH GOOD PACKING WITHIN THE 12Z ECMWF ENSEMBLES TO BOOST CONTINUED CONFIDENCE. THE 00Z UKMET SIMILAR TO ITS PRIOR RUN MAY HAVE A BIT OF FEED BACK ISSUES RESOLVING STRONG/CONCENTRIC SHORTWAVE FEATURES AT 5H AND MAY BE OVER DOING THE STRENGTH/QPF SIGNAL PARTICULARLY WITH THE SOUTHERN VORT ACROSS THE WESTERN CAP ROCK. STILL AVERAGE CONFIDENCE IN A PREFERENCE OF A 00Z ECMWF/CMC/UKMET BLEND. WEAK UPPER LOW MIGRATING ACROSS THE SOUTHEAST CONVECTIVE LOW MOVING INTO/OFFSHORE THE SOUTHEAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z OPERATIONAL MODELS CONFIDENCE: AVERAGE THE 00Z CMC HAS WEAKENED ITS DEEPER SURFACE LOW...EVEN THOUGH IT REMAINS THE DEEPEST...INTERACTION WITH THE UPPER LOW AS IT RETROGRADES AND THE WEAK E-W RIDGING OVER THE MID-ATLANTIC BRING IT CLOSER TO THE FOLD OF THE OTHER DETERMINISTIC MODELS. THE 00Z ECMWF ALONG WITH THE 00Z CMC/UKMET START PULLING ENERGY OUT OF THE NORTHWEST CARIBBEAN ACROSS CUBA AND BACK AROUND THROUGH THE CAROLINAS...PUMPING MOISTURE AND FOCUSING MECHANISMS TO INCREASE CONVECTIVE DEVELOPMENT/QPF. THE 00Z GFS/NAM ARE NOT FAR OFF THIS SOLUTION EITHER WITH THE GFS A BIT WEAKER AND FURTHER NORTH WITH THE UPPER LOW. THIS MAKES THE 00Z GFS ALSO HAVE INCREASED INTERACTION WITH A DRAPED FRONTAL ZONE UNDER THE RIDGING AXIS WHICH IS SUPPORTED BY THE UKMET AND CMC... AND LESS SO THE NAM....WHILE THE 00Z ECMWF IS NEARLY NEGLIGIBLE UNTIL SATURDAY. THE EARLIER PREFERENCE OF THE GFS/ECMWF WOULD ENCOMPASS ALL THE SOLUTIONS. AS SUCH A BLEND OF THE OPERATIONAL MODELS IS PREFERRED GIVEN MUCH OF THE DETAILS ARE IN MESOSCALE CONVECTIVE INTERACTIONS...THOUGH WITH WEAK SYSTEMS THIS BLEND IS ONLY AVERAGE IN CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA