MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1257 AM EDT SAT OCT 08 2016 VALID OCT 08/0000 UTC THRU OCT 11/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HURRICANE MATTHEW ~~~~~~~~~~~~~~~~~~~~ PREFERENCE: PLEASE SEE 03Z NHC FORECAST MODELS QUICKLY DIVERGE AFTER 36HR ONCE THE SYSTEM STARTS MOVING EAST (SOUTH OF THE NC COASTLINE. THE 00Z NAM AND 12Z ECMWF REMAIN A BIT SLOWER AND KEEP WITH CONTINUITY MAKING THE ANTICYCLONIC LOOP. THE 12Z CMC IS NEXT CLOSEST ALONG WITH THE 18Z GEFS. THE 12Z UKMET IS MUCH FURTHER NORTH AND ACTUALLY STARTS TO STALL ABOUT HALFWAY BETWEEN BERMUDA AND THE NJ COAST (NEAR 75W)...NOT MAKING THE ANTICYCLONIC LOOP. THE NEW GFS CONTINUES TO BE A NORTHWEST MEMBER COMPARED TO THE 18Z GEFS SOLUTIONS BEGINNING A BINARY INTERACTION WITH NICOLE OUT NEAR 30N75W. THE OFFICIAL NHC GUIDANCE APPEARS TO BE BETWEEN THE 12Z ECMWF AND 12Z CMC/18Z GEFS SOLUTIONS. AS NOTED IN THE 03Z NHC DISCUSSION...THE CONFIDENCE IS QUICK LOW AFTER 36HRS. UPPER-LEVEL TROUGH CROSSING THE UPPER MIDWEST/UPPER GREAT LAKES TODAY SHIFTING ACROSS NEW ENGLAND THRU MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND PRIOR TO 09/12Z 00Z NAM/18Z GEFS/12Z ECMWF BLEND THEREAFTER CONFIDENCE: ABOVE AVERAGE PRIOR TO 09/12Z AVERAGE AFTERWARD THE MODELS ARE ALL IN GOOD AGREEMENT WITH THE CURRENT CONFIGURATION OF SHORTWAVE/LONGWAVE ENERGY WITH RESPECT TO THE UPPER LEVEL LOW/TROF ACROSS CANADA SHIFTING EASTWARD THROUGH SE CANADA AND GREAT LAKES BY SAT NIGHT. THE SPREAD THAT OCCURS AFTER SATURDAY IS INTRODUCED BY THE PHASING OF A FAST MOVING SHORTWAVE CURRENTLY IN THE PACIFIC NORTHWEST. THIS SHORTWAVE REACHES THE SW PERIPHERY OF THE MEAN TROF SUNDAY MORNING ACROSS THE CENTRAL/LOWER GREAT LAKES...WHEN IT BEGINS TO AMPLIFY THE TROF THROUGH THE UPPER MID-ATLANTIC/NEW ENGLAND. THE 12Z UKMET AND 00Z GFS REMAIN THE MOST AMPLIFIED AND LEAD TO THE LARGEST INTERACTION WITH THE REMAINING MID-LEVEL ENERGY OF MATTHEW (SEE SECTION ABOVE). IRRESPECTIVE OF THIS INTERACTION...ALL MODELS DO SUPPORT COASTAL SURFACE CYCLOGENESIS ALONG THE FRONT BETWEEN MATTHEW AND NOVA SCOTIA. THE 00Z GFS BEING A BIT MORE AMPLIFIED IS A BIT SLOWER TRENDING AWAY FROM THE BETTER CLUSTERING NORTHEAST. THE 12Z ECMWF - MOST FLAT - IS LEADING THE CLUSTER FURTHER EAST. WHILE THE 18Z GEFS DOES HINT AT THE TROF THE 00Z GFS MAY BE A BIT TOO ENHANCED TO BE FULLY CONSIDERED...BUT MAY BE ONTO A TREND. THE 12Z CMC IS ALSO A BIT FAST LIKE THE ECMWF BUT SEEMS TO FAVOR A FURTHER NORTH SOLUTION/PLACEMENT OF VORT ENERGY. AS SUCH WILL FAVOR A 00Z NAM/18Z GEFS/12Z ECMWF BLEND AFTER 9/12Z...AT AVERAGE CONFIDENCE. PRIOR TO 09/12Z...A GENERAL MODEL BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE. UPPER LOW/POSITIVELY TILTED TROUGH IN BRITISH COLUMBIA. SFC LOW EMERGING EAST OF THE ROCKIES LATE SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS AND 12Z ECMWF/CMC BLEND CONFIDENCE: AVERAGE THE UPPER-LEVEL LOW INITIALLY OFF THE COAST OF BRITISH COLUMBIA IS FORECAST TO MOVE SOUTHEAST AND GRADUALLY OPEN INTO A POSITIVELY TILTED TROUGH BY SUNDAY. DIFFERENCES IN THE MODELS SEEM TO BE RELATED TO SPEED...BOTH WITH THE NORTHEAST WAVE WITHIN THE TROF CROSSING SOUTHERN CANADA (SUPPORTING THE SURFACE LEE CYCLOGENESIS SOUTEHRN CANADA TO NW ONTARIO LATE SUNDAY INTO MONDAY) AS WELL AS THE BASE OF THE TROF CROSSING THE NORTHERN US ROCKIES BY TUESDAY. THE OVERALL SHAPE/ORIENTATION...IE PATTERN SEEM TO BE FAIRLY WELL AGREED UPON THOUGH. THE 12Z UKMET FAVORS A FASTER/DEEPER LEAD WAVE AND DUE TO LESS INFLUENCE STALLS/LAGS THE WESTERN BASE OF THE TROF. THE 00Z NAM APPEARS VERY SLOW IN THE LOWEST LEVELS AND REMAINS DEEPER THAN MUCH OF THE REST OF THE GUIDANCE. THE REMAINING GUIDANCE (12Z ECMWF/CMC AND 00Z GFS) HAVE SLIGHT DIFFERENCES BUT THE TIMING/ORIENTATION OF THE TROF ALOFT AND FRONTAL ZONE ACROSS THE NORTHERN PLAINS SEEMS TO MELD WELL. WILL FAVOR A HIGHER WEIGHTING TO THE 00Z GFS WHICH HAS TRENDED TOWARD THE MIDDLE SOLUTION AND REPRESENTS THE ENSEMBLE MEANS WELL. CONFIDENCE IN A 12Z ECMWF/CMC AND 00Z GFS BLEND IS AVERAGE GIVEN THE OVERALL PATTERN IS WELL HANDLED...BUT THE FINE (BUT IMPORTANT DETAILS) STILL ARE JUST OUT OF PHASE. EASTERN PACIFIC/BAJA TROUGH LIFTING INTO THE SOUTHWEST SUN AND INTO THE PLAINS BY MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: AVERAGE THE BROAD TROUGH OVER THE EASTERN PACIFIC/N BAJA CALIFORNIA WILL CONTINUE TO REMAIN DISORGANIZED/SHEARED IN APPEARANCE AS IT LIFTS INTO THE FOUR CORNERS REGION BY SUNDAY...MODELS SHOW FAIRLY GOOD AGREEMENT UNTIL CROSSING THE ROCKIES INTO THE PLAINS INTO INCREASINGLY CONFLUENT FLOW LEADING TO TIMING DIFFERENCE. THE 12Z UKMET LEADS THE PACK AND SHEARS FASTER INTO THE FLOW...WHICH SEEMS A BIT OUT OF PLACE GIVEN THE DOWNSTREAM AMPLIFIED FLOW. LIKEWISE THE CMC FOLLOWED BY THE ECMWF ARE SLIGHTLY FASTER THAN THE 00Z GFS/NAM BUT SEEM MORE PLAUSIBLE GIVEN THEIR DOWNSTREAM PATTERN. GIVEN THE DIFFERENCES ARE FAIRLY SMALL WILL FAVOR A NON-UKMET BLEND FOR THIS FEATURE AS IT WASHES OUT INTO THE GREAT LAKES. CONFIDENCE REMAINS AVERAGE. WEAKENING PACIFIC TROF SLIDES THROUGH SOUTH CA BY TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: AVERAGE STRONG DEEP CYCLONE OUT NEAR 40N150W WILL DESCEND IN LATITUDE AND WEAKEN A BIT AS IT UNDERCUTS THE MEAN RIDGE OVER THE NORTHEAST PACIFIC...EVENTUALLY SHIFTING EAST TOWARD THE CENTRAL/SOUTHERN CA COAST BY EARLY TUESDAY. GIVEN THE DIGGING TROF ACROSS THE NORTHWEST FLOW SHOULD BE INCREASINGLY CONFLUENT SHEARING THE REMAINING ENERGY ACROSS CA INTO THE LOWER COLORADO BASIN BY THE END OF THE FORECAST PERIOD. THE 00Z NAM REMAINS MOST AMPLIFIED AND QUITE CONSOLIDATED SLIGHTLY FASTER THAN THE ENSEMBLE MEAN. THE 12Z UKMET IS ALSO A BIT MORE AMPLIFIED AND MUCH FASTER TRENDING AWAY FROM THE ENSEMBLE MEAN TOO. BOTH SEEM TO HAVE SOME TIMING ISSUES WITH THE NORTHERN STREAM WAVE AND ARE LESS FAVORABLE THERE...WHICH SEEMS TO LEAD TO ISSUES WITH THIS WAVE HERE TOO. AS SUCH WILL FAVOR THE ENSEMBLE MEANS WHICH ARE WELL REPRESENTED BY THE 00Z GFS AND 12Z ECMWF. CONFIDENCE IN AVERAGE GIVEN SPREAD THOUGH SOME CONSISTENCY WITH THE MEANS OVER THE PAST FEW CYCLES. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA