MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1244 AM EDT SUN OCT 25 2015 VALID OCT 25/0000 UTC THRU OCT 28/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FORECAST PREFERENCE AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TROUGH OVER THE CENTRAL/NORTHERN PLAINS MERGES WITH NORTHERN STREAM TROUGH LOW PRESSURE TRACKING TO THE GREAT LAKES SAT AND COLD FRONTAL PASSAGE THRU NEW ENGLAND/MID-ATLANTIC SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: MODEL CONSENSUS CONFIDENCE: ABOVE AVERAGE MODELS REMAIN IN OVERALL STRONG AGREEMENT WITH THIS SYSTEM. LONG WAVE TROUGH ENTERING THE PACIFIC NORTHWEST SUN CROSSING THE ROCKIES AND EJECTING INTO CENTRAL PLAINS BY TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 18Z GEFS/12Z ECENS MEAN/21Z SREF CONFIDENCE: BELOW AVERAGE AS NOTED IN PRIOR DISCUSSIONS...A COMPLEX PATTERN CONSISTS OF THREE SIGNIFICANT FEATURES THAT INTERACT TOWARD THE DEVELOPMENT OF AN AMPLIFIED LONG WAVE TROUGH ENTERING THE PACIFIC COAST TODAY INTO MONDAY. THE MAIN FEATURE BEING THE TIGHTLY WRAPPED UP CYCLONE CURRENTLY NEAR 44N 130W. FURTHER NORTH...ENERGY FROM A SHORTWAVE OVER THE GULF OF ALASKA IS FORECAST TO CROSS THE NORTHERN CANADIAN ROCKIES AND OVER THE TOP OF THE UPPER LEVEL RIDGE ON THE LEE OF THE MOUNTAINS. TO COMPLICATE THE EVOLUTION FURTHER...AN INCREASINGLY MORE DEFINED SHORTWAVE SHED FROM TC OLAF AS WELL AS A SUBTROPICAL WAVE LOCATED 33N 130W IS PHASING WITH THE WRAPPED UP CYCLONE ENERGY...TO FORM THE BASE THE TROF. OVERALL...THERE IS GOOD AGREEMENT WITH THE GLOBAL MODELS AND THEIR ENSEMBLE FORECASTS THROUGH LANDFALL OF THE SURFACE CYCLONE SUN NIGHT. AFTER THAT TIME...THERE APPEAR TO BE TWO CAMPS OF SOLUTIONS WITH FASTER SOUTHERN SOLUTION BUT SLIGHTLY STALLED AND WIDER SOLUTION CROSSING THE NORTHERN ROCKIES REPRESENTED BY THE 00Z NAM/00Z GFS AND A SLIGHTLY SLOWER SUBTROPICAL WAVE...ALLOWING IT TO DRAW A MORE CONSOLIDATED THOUGH SMALLER CENTROID OF SHORTWAVE ENERGY FROM THE NW COAST CYCLONE AND DROP IT SOUTH THROUGH UT/CO...KEEPING THE OVERALL TILT OF THE TROF MORE NARROW AND VERTICALLY ALIGNED NORTH TO SOUTH REPRESENTED BY THE 12Z ECMWF/UKMET. THE 00Z NAM IS A BIT STRONGER RESOLVING EACH FEATURE COMPARED TO THE 00Z GFS...TYPICAL OF ITS BIAS...BUT THIS ALSO LEADS TO DIFFERENCES IN TIMING MAKING THE EVOLUTION ABOUT 6-12 HOURS FASTER WITH THE 00Z NAM. OVERALL...EACH DETERMINISTIC MODEL CAMP APPEARS TO BE ON THE OUTER FRINGES OF THE ENSEMBLE SPAGHETTI CHARTS...REDUCING CONFIDENCE IN FAVORING ANY PARTICULAR SOLUTION. THE 12Z UKMET IS LIKELY THE BEST MOST CENTRAL OF THE OPERATIONAL MODELS WITH THE NORTHERN PLAINS...BUT IS MUCH DEEPER INTO THE SOUTHERN PLAINS THAN OTHER OPERATION MODELS OR THE ENSEMBLE MEANS COULD SUPPORT JUSTIFYING AS PREFERENCE. THE 12Z GEFS/12Z ECENS MEANS...WHICH ARE SUPPORTED WITH THE 18Z GEFS AND 21Z SREF IN GENERAL ARE MORE NEUTRAL THOUGH MAY BE LOSING A BULK OF THE DEPTH/CONSOLIDATED STRENGTH ACROSS THE DAKOTAS BY DAY 3...AS TO BE EXPECTED BY THE WEAKNESS INHERENT IN AVERAGING. STILL THE OVERALL PLACEMENT/TIMING AND EVOLUTION IN THESE MEANS IS PREFERRED BY WPC AT THIS TIME...AND WITH OUT MUCH OPERATIONAL REPRESENTATION OPERATIONALLY CONFIDENCE IS WELL BELOW AVERAGE. COMBINED SHORTWAVE ENERGY INCLUDING REMNANTS OF TC PATRICIA CROSSING THE NORTHWESTERN GULF COAST SHEARING INTO TENNESSEE RIVER VALLEY TUES/WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF OR 18Z GEFS/12Z ECENS MEAN CONFIDENCE: AVERAGE OVERALL MUCH OF THE MODEL SUITE IS QUITE AGREEABLE THROUGH LATE MONDAY/TUESDAY MORNING WHEN THE SYSTEM STARTS TO BE AFFECTED BY THE UPSTREAM LONG WAVE TROF. IN FACT MUCH OF THE DIFFERENCES IN THE MODEL SOLUTIONS COULD MORE OR LESS BE ATTRIBUTED TO SAID AFFECTS OF THE APPROACHING WAVE. OVERALL THE 18Z GEFS CONTINUES TO BE MIDDLE GROUND BUT WITH STRENGTHENED SUPPORT OF THE 12Z ECENS MEAN AND THE 00Z GFS CONTINUES TO SERVE AS THE BEST REPRESENTATION OF THESE ENSEMBLE MEANS. THE 00Z NAM IS ALSO IN LINE WITH THE GFS BEFORE DEEPENING A BIT STRONGER AND LIFTING FASTER NNE ACROSS THE LOWER GREAT LAKES BY WED UNDER THE INFLUENCE OF THE STRONGER UPSTREAM TROF...MAKING IT LESS ALIGNED WITH OTHER MODELS AFTER DAY 2. EVEN THOUGH THE 12Z OPERATIONAL ECWMF TENDS TO WEAKEN FASTER AT THE SURFACE THE INFLUENCES OF A SLIGHTLY FASTER BASE OF THE UPSTREAM TROF COMPARED TO THE NAM/GFS KEEPS THE WEAKENED TROF/ENERGY AND QPF SHIFTING NORTHWARD THROUGH THE MISSISSIPPI RIVER VALLEY IN CLOSE PROXIMITY TO THE NAM/GFS SOLUTIONS. THE 12Z CMC/UKMET ALSO HAVE SIMILAR EVOLUTIONS TO THE 12Z ECMWF WITH A SLOWER EJECTION/SHEARING OF THE ENERGY COMPARED TO THE 00Z NAM AND GFS...BUT DIFFERENCES SEEM SMALL COMPARED TO PRIOR RUNS. CONTINUITY PLACES SOME STRENGTH IN RETAINING GFS/ECMWF BLEND...WHICH WOULD BE SUFFICIENT TO BEST REPRESENT THE ENSEMBLE SPREAD...THOUGH A LITTLE GREATER WEIGHTING TOWARD THE GFS. WITH OVERALL STRENGTH OF THE ENTIRE SUITE...CONFIDENCE IS INCREASING BUT TEMPERED BY THE HIGH VARIABILITY INTRODUCED FROM THE UPSTREAM TROF...AS SUCH CONFIDENCE IS JUST AVERAGE. NEXT LONG WAVE TROF AFFECTING THE CANADIAN/U.S. PACIFIC COAST BY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z ECMWF/CMC WITH 12Z ECENS MEAN CONFIDENCE: BELOW AVERAGE A DRAMATIC SHIFT IN THE 00Z NCEP GUIDANCE COMPARED TO THE 12Z RUNS...NOW DEEPENS THE APPROACHING EASTERN PACIFIC TROF MORE AGGRESSIVELY EVEN SURPASSING THE 12Z ECMWF/CMC AND THE 12Z ECENS MEAN...AS WELL AS BEING A BIT SLOWER. THIS IS SO DRAMATIC THE 12Z ITERATION OF THE SPAGHETTI DIAGRAMS PLOTS HAD AS FEW AS ONE GEFS MEMBER EVEN HINTING AT A DEEPER TROF. THE 12Z UKMET REMAINED GENERALLY ZONAL. TO COMPOUND ISSUES...BOTH THE 00Z NAM/GFS DRAW TC OLAF TOWARD THE COAST...WELL DEPARTING FROM CURRENT FORECAST TRACK FROM CPHC. LOOKING AT GOES-WEST WV...IT APPEARS THAT THE DEEPER TROF SEEN BY THE DARKENING DRYING AND ASSOCIATED ENERGY NORTH OF HAWAII PLACES OLAF IN A HIGHLY VARIABLE OR TEETERING POSITION. OVERALL THIS SEEMS A BIT TOO DRAMATIC OF A SHIFT TO SUPPORT THE 00Z NAM OR GFS...BUT CLEARLY BARES WATCHING IN SUBSEQUENT MODEL RUNS. HOWEVER...THE NCEP SUITE'S 00Z SHIFT DOES SUPPORT THE DEEPER MEAN TROF APPROACHING THE COAST PROVIDING CONFIDENCE IN A 12Z ECMWF/CMC/ECENS MEAN BLEND. STILL WITH ALL THIS VOLATILITY CONFIDENCE IS BELOW AVERAGE AS A WHOLE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA