MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1212 AM EST SAT JAN 02 2016 VALID JAN 02/0000 UTC THRU JAN 05/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DEEP CYCLONIC FLOW EXTENDING OVER MUCH OF EASTERN SECTIONS OF NORTH AMERICA THROUGH MON SURFACE WAVE TRACKING THROUGH SOUTHERN QUEBEC 03/06Z ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND THROUGH 04/00Z 00Z GFS/NAM/12Z UKMET BLEND 04/00Z - 05/12Z CONFIDENCE: SLIGHTLY BELOW AVERAGE DIFFERENCES WITH TWO OF THE MORE SIGNIFICANT SHORTWAVES EMBEDDED WITHIN UPPER TROUGHING WILL BE DISCUSSED IN THIS SECTION. THE FIRST SHORTWAVE MOVES OVER THE GREAT LAKES SAT NIGHT AND PRODUCES A SURFACE LOW IN SRN ONTARIO/QUEBEC. THE DIFFERENCES HERE ARE RELATIVELY MINOR AND HAVE TO DO WITH TIMING OF WHEN THE TROF BOTTOMS OUT ACROSS THE GREAT LAKES. THE 12Z ECMWF IS A BIT SLOWER/WEST INITIALLY WITH THE 00Z NAM/12 UKMET NORTH...THOUGH THE ECMWF TRENDS NORTH CLOSE TO THE 00Z GFS TRACK. THE 12Z CMC IS INITIALLY CENTRAL TO THE LOW BUT BECOME SOUTHERN MEMBERS TO THE CLUSTER AS THE WAVE TRANSLATES ACROSS NORTHERN NEW ENGLAND. THE GEFS/SREF AND ECENS MEANS SPLIT THE SMALL DIFFERENCE ABOUT HALF WAY BETWEEN THE 00Z AND 12Z ECMWF....BUT CLUSTER WELL BY SUNDAY AFTERNOON IF A SHADE SOUTH OF THE GFS/ECMWF...BUILDING FAIRLY GOOD CONFIDENCE IN THE GFS/ECMWF BLEND WITH THIS WAVE. THE SECOND SHORTWAVE ARRIVES QUICKLY ON THE HEELS OF THE FIRST AND IS DEEPER WITH A STRONG MERIDIONAL PUSH ACROSS W ONTARIO INTO THE CENTRAL GREAT LAKES BY MID-DAY MONDAY. THE 12Z CMC GENERALLY PLACES MORE ENERGY INTO THE BASE OF THE TROF...NARROWING IT AND SHIFTING IT EASTWARD OFF THE COAST BY THE END OF THE FORECAST PERIOD OUTPACING THE REST OF THE GUIDANCE. ON THE OTHER SIDE OF THE SPECTRUM...THE 12Z ECMWF ALSO DROPS A LARGE PORTION OF ENERGY INTO THE BASE BUT OVERALL SLOWS...INCREASING THE POSITIVE TILT TO THE TROF OVERALL. THE 00Z NAM/GFS AND 12Z UKMET ARE MORE CENTRAL WITHIN THE LARGE SPREAD IN ENSEMBLE SUITE. THE 12Z ECENS MEAN SUPPORTS ITS OPERATIONAL RUN...BUT WITH ONLY A LARGE SPREAD WEST TO EAST OF ECMWF MEMBERS SUPPORTING THIS SLOWER TROF...IT SEEMS A BIT UNLIKELY. THEREFORE...THE BEST APPROACH TO THE ENTIRE NORTHEASTERN REGION THROUGH MONDAY IS TO GO WITH THE 00Z GFS ...WITH BLENDS OF THE 12Z ECMWF WITH THE FIRST WAVE FOR TIGHTEST AGREEMENT WHILE INCLUDING THE 00Z NAM/12Z UKMET FOR THE SECONDARY/DEEPER TROF. GIVEN THIS SPLIT IN MODEL PREFERENCE AND OVERALL SPREAD...CONFIDENCE IS SLIGHTLY BELOW AVERAGE (PARTICULARLY FOR THE SECOND TROF). WEAK IMPULSE CROSSING THE LOWER RIO GRANDE BY SATURDAY EVENING SHIFTING ACROSS THE GULF TOWARD FLORIDA BY MONDAY. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS AND 12Z ECMWF/UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 00Z NAM HAS DEVELOPED THE NORTHERN STREAM ENERGY SHEARING OUT OF THE CENTRAL ROCKIES IN LINE WITH OTHER GUIDANCE...THOUGH FAST BUT REMAINS COMPARATIVELY SLOW IN THE THE SOUTHERN STREAM. AS SUCH THE FEATURES TIMING LEADS TO INCREASED PHASING OR EVEN THE NORTHERN STREAM OUTPACING THE SOUTHERN EVER SO SLIGHTLY LEADING TO A SLIGHTLY SLOWER FRONTAL PUSH ACROSS FLORIDA BY MONDAY EVENING. THE 00Z GFS LIKE THE NAM BEGAN TO ENHANCE THE SMALL BUT TIGHT NORTHERN STREAM SHORTWAVE BUT IS ALSO A BIT FAST WITH IT...HOWEVER THE SOUTHERN STREAM FEATURE IS IN FAIRLY GOOD AGREEMENT IN PLACEMENT/TIMING TO ALLOWS THE GFS TO BE A BIT MORE PROGRESSIVE TOWARD THE SOUTH AND EAST OF OTHER REMAINING MODELS. THE 12Z ECMWF IS GENERALLY THE SLOWEST OF THE MAIN DETERMINISTIC MODELS AND HAS THE LARGEST GAP IN SPACING BETWEEN THE NORTHERN AND SOUTHERN STREAM ENERGIES...AND IS SUPPORTED WELL BY THE 12Z UKMET (IF NOT A BIT SOUTH AND FASTER WITH THE NORTHERN STREAM WAVE). THE 12Z CMC IS THE ONLY HOLDOUT OF A WEAKER NORTHERN STREAM FEATURE AS WELL AS BEING A BIT MORE PROGRESSIVE IN THE SOUTHERN STREAM WHICH BROADENS THE SURFACE RESPONSE EAST OF FLORIDA AND EXPANDS THE QPF NORTHWARD. UNSURPRISINGLY THE ENSEMBLE MEANS SUPPORT THEIR OWN CAMPS...BUT THE 12Z AND 18Z GEFS MEMBERS ARE CLUSTERED VERY TIGHTLY TOWARD THE GFS SOLUTION...STRENGTHENING ITS RESOLVE. THE SMALL DIFFERENCES IN TIMING ACROSS THE NORTHERN STREAM ARE MINOR COMPARED TO THE SMALL DIFFERENCES AND TIGHTER ENSEMBLE AGREEMENT TO INCLUDE THE 00Z GFS INTO THE 12Z ECMWF/UKMET BLEND. CONFIDENCE REMAINS SLIGHTLY ABOVE AVERAGE. CLOSED LOW OVER THE WEST COAST THIS MORNING...LIFTING NORTH INTO SWRN CANADA THROUGH MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/NAM AND 12Z ECMWF BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE SIZABLE SPREAD REMAINS IN THE LATEST ENSEMBLE SPAGHETTI PLOTS WITH THE POSITION/TIMING OF THE WESTERN CLOSED LOW AND MEAN RIDGE AXIS GENERALLY AFTER IT LIFTS NORTH ACROSS THE PACIFIC NORTHWEST INTO SOUTHWESTERN CANADA WITH ONLY THE 12Z UKMET BREAKING EAST TOWARD THE SOUTHERN CANADIAN ROCKIES BY 05/00Z. THE 12Z CMC AND 00Z GFS REMAIN SLIGHTLY WEST OF THE MEAN RIDGE AXIS AND WEAKEN AND LIFT NORTH-NORTHWESTWARD...CMC SLIGHTLY FASTER. THE 00Z NAM LIFTS THE BULK OF THE ENERGY INTO THE MEAN RIDGE RE-ESTABLISHING A REX SHAPE BY THE END OF THE FORECAST WHILE THE ECMWF IS MIDDLE GROUND TO THIS SOLUTION. THROUGHOUT THIS PROCESS...OCCASIONALLY RETURN FLOW ON THE EASTERN SIDE OF THE RIDGE AXIS SHEARS SOME ENERGY INTO THE THE WNW OR NW FLOW ACROSS CENTRAL CANADA...LEADING TO LITTLE DIFFERENCES IN SHAPE OF MASS FIELD BUT LITTLE SENSIBLE WEATHER DIFFERENCES. OVERALL...IT APPEARS THROUGH THE ENSEMBLES THAT THE MAJORITY OF ENSEMBLE MEMBERS SUPPORT THE ENERGY REMAINING NEAR BUT JUST WEST OF THE RIDGE AXIS...SUPPORTING A GFS/ECMWF/NAM BLEND...THOUGH WEIGHTING TOWARD THE MOST CENTRAL ECMWF MEMBER. CONFIDENCE IS INCREASING BUT REMAINS SLIGHTLY BELOW AVERAGE. SRN PORTION OF MID-UPPER LEVEL TROUGH NEARING THE WEST COAST EARLY THIS WEEK...REACHING THE NRN BAJA PENINSULA EARLY MON MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/21Z SREF/12 ECMWF BLEND CONFIDENCE: AVERAGE THERE IS FAIRLY STRONG AGREEMENT WITH THE 00Z NAM/GFS AND 12Z ECMWF CENTRAL TO A MODERATE SPREAD IN THE ENSEMBLES AND AS SUCH ARE IN LINE WITH THE 12Z ECENS MEAN/18Z GEFS AND 21Z SREF. THE 12Z ECMWF IS GENERALLY A BIT DEEPER THAN THE 00Z GFS...AND BECOMES A BIT FASTER EVEN THAN ITS ECENS MEAN. SIMILARLY THE 00Z NAM IS A BIT FAST TO THE BEST CLUSTERING AS WELL ALSO OUTPACING THE SREF MEAN. THE 12Z CMC IS VERY DEEP PLACING MUCH OF THE BASE OF THE TROF WELL INTO NW MEXICO. THE 12Z UKMET HAS INTERACTION DIFFERENCES DUE TO CLOSER PROXIMITY TO NORTHERN STREAM ENERGY AND IS CLEARLY AN OUTLIER TO THE OVERALL SUITE. OVERALL CONTINUITY REMAINS FAVORING THE 00Z GFS/12Z ECMWF BUT INCLUSION OF THE 21Z SREF SHOULD GARNER SOME INCREASED SUPPORT GIVEN ITS FAIRLY GOOD AGREEMENT WITH THE GFS/ECMWF. NRN PORTION OF MID-UPPER LEVEL TROUGH NEARING THE WEST COAST EARLY THIS WEEK...REACHING INVOF NRN CALIFORNIA EARLY MON MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: AVERAGE THE 00Z NAM HAS SHIFTED TOWARD THE ECMWF/GFS SOLUTION ACTUALLY GOING THROUGH THE WOBBLE IN THE UPPER LOW/SURFACE LOW WEST OF 130W ON SAT NIGHT/SUN MORNING A BIT LESS THAN THE 00Z GFS/ECMWF...ONLY DIFFERENCE IS THE STRENGTH OF THE LOW IS A BIT DEEPER THOUGH ITS EVOLUTION...BUT IT MAY BE ON TO SOMETHING...BUT AT THIS TIME COULD BE ADDED BUT AT A LESSER WEIGHTING OR INCREASE THE CONFIDENCE BY JUST RETAINING THE 00Z GFS/12Z ECMWF BLEND. THE 12Z UKMET IS WELL TOO FAR SOUTH. THE 12Z CMC IS A BIT NORTH AND BECOMES A BIT FAST AFTER SWINGING THROUGH THE WOBBLE ADVANCING EAST A BIT MUCH BY MONDAY AFTERNOON...LIKE THE NAM...IT COULD BE INCLUDED BUT WOULD BROADEN THE OTHERWISE TIGHTER CLUSTER THAT ALSO HAS STRONG ENSEMBLE AND CONTINUITY SUPPORT IN THE 00Z GFS/12Z ECMWF BLEND. CONFIDENCE IS AVERAGE NEXT APPROACHING PACIFIC TROF NEARING THE WEST COAST TUESDAY NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: BELOW AVERAGE THE NEXT APPROACHING PACIFIC TROF NEARS THE WEST COAST BY THE END OF THE FORECAST PERIOD...ENSEMBLE TRENDS NOTED A BIT OF INCREASED SPREAD IN THE HEIGHT SPAGHETTI PLOTS MAINLY IN TIMING...AS SOME OF THE MODELS TRENDED FASTER. THIS WAS GENERALLY LEAD BY THE 12Z ECMWF...FOLLOWED CLOSELY BY THE 00Z GFS...WITH FAIRLY GOOD AGREEMENT IN TIMING/PLACEMENT AND OVERALL DEPTH OF THE TROF. THE 12Z ECENS MEAN AGREES WITH THIS SOLUTION BRINGING SOME CONFIDENCE. HOWEVER...THE 18Z GEFS/12Z CMC FOLLOWED BY THE 00Z NAM AND SREF LAG BY A FEW DEGREES OF LONGITUDE AND THE NAM/SREF ARE GENERALLY BROADER AND LESS DEEP. THE 12Z UKMET IS THE SLOWEST WHICH IS HIGHLY ATYPICAL BUT WITH OTHER LARGE DISAGREEMENTS ACROSS THE PACIFIC BASIN EXISTING...LITTLE FAITH IS GIVEN TO ITS SOLUTION AT THIS TIME. GIVEN THE TYPICALLY MORE RELIABLE MODELS ARE IN GOOD AGREEMENT AND THEY HAVE GOOD AGREEMENT DOWNSTREAM...WILL SUPPORT A 00Z GFS/12Z ECMWF BLEND...BUT AT BELOW AVERAGE CONFIDENCE GIVEN THE LARGE SPREAD AND SHIFT IN TIMING. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA