MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 136 PM EST FRI DEC 02 2016 VALID DEC 02/1200 UTC THRU DEC 06/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHORTWAVE AMPLIFYING INTO A CLOSED LOW ACROSS NORTHERN MEXICO SAT/SUN LIFTS INTO TX BY MON SPURRING SURFACE LOW DEVELOPMENT IN WESTERN GULF MON LIFTING INTO LOWER MS VALLEY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/ECMWF BLEND CONFIDENCE: AVERAGE THE LARGER SPREAD CONTINUES TO EVAPORATE WITH THE CAMPS FROM A FEW DAYS AGO SWAPPING POSITIONS: GFS/UKMET FASTER AND ECMWF/NAM SLOWER. THE 00Z ECMWF CONTINUES TO BE SLOWER AND MORE WOUND UP THAN THE MAJORITY OF THE 00Z ECENS MEMBERS MAKING THE ECENS MEAN UNCHARACTERISTICALLY FAST ESPECIALLY IN A DEEP SOUTHERN CUT-OFF ENVIRONMENT. OVERALL MODELS ARE IN GOOD ALIGNMENT IN EVOLUTION SHAPE/TIMING/STRENGTH THROUGH THE NORTHERN MX PLATEAU THROUGH SUN. TIMING/RETENTION OF STRENGTH DIFFERENCES EXPAND THE SPREAD SLIGHTLY AS THE UPPER LOW CROSSES THE NORTHERN SIERRA MADRE ORIENTAL. THIS IS MOST EVIDENT IN THE 12Z NAM...NOW THE SLOWEST RETAINING THE STRENGTH OF THE UPPER LOW. THIS IS OPPOSITE OF ITS POSITION IN THE SOLUTION OVER THE PAST FEW DAYS...MAKING IT LOWER CONFIDENCE IN USING IT WITHIN THE BLEND. THE 12Z GFS LIKE THE 06Z GFS ARE A BIT WEAKER TRAVERSING MEXICO AND BECOME FASTER EVEN AND BECOME AN OPEN WAVE BY MON EVENING COMPARED TO THE 00Z GFS/06Z GEFS BUT IS ALSO COMPARABLE TO THE 00Z GFS PARALLEL AND 00Z ECMWF. THE 00Z UKMET/CMC ALSO MATCH WITH TIMING OF THE ECMWF/GFS THOUGH THE UKMET IS A BIT FURTHER NORTH WITHIN THE SUITE. ALL CONSIDERED A NON-NAM BLEND (NOR 09Z SREF/00Z ECENS MEAN) IS PREFERRED IN THE A BLEND. CONFIDENCE IN THESE SOLUTIONS IN THE BLEND IS INCREASING TO THE POSITIVE SIDE OF AVERAGE. 19Z UPDATE: THE 12Z GEFS MEMBERS CONTINUE TO SHOW THE UNCERTAINTY WITH RESPECT TO DAY 3 IN THE TIMING/HOW LONG TO MAINTAIN A CLOSED SYSTEM AND THEREFORE THE MEAN LAGS THE OPERATIONAL 12Z GFS. THIS IS FURTHER COMPOUNDED BY THE 12Z UKMET TRENDING FASTER WHILE THE 12Z CMC TRENDED SLOWER IN THE REALM OF THE 12Z NAM. THE 12Z ECMWF CONTINUES WITH CONSISTENT TIMING BUT LIKE THE GFS IS A BIT WEAKER THAN PRIOR RUNS. THE MIDDLE GROUND IS BEST REPRESENTED BY THE 12Z GFS/ECMWF AND SO WILL EXCLUDE THE 12Z VERSIONS OF THE UKMET/CMC FROM THE PREFERENCE. CONFIDENCE REMAINS AVERAGE. SHORTWAVE CROSSING SOUTHWEST CANADA FRI...NORTHERN PLAINS SAT...WESTERN GREAT LAKES SUNDAY...NEW ENGLAND MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE LINGERING SHORTWAVE ENERGY ACROSS W WY AT THIS TIME WILL BE LIFTED/COMBINED WITH ENERGY AT THE LEADING EDGE OF 150+ KT JET ENTERING THE PACIFIC NORTHWEST TODAY. AS THE WAVE CONSOLIDATES CROSSING THE ROCKIES THERE REMAINS SOME WEAK PHASED NATURE WITH THE SOUTHERN STREAM CUT-OFF AND INCREASE IN AMPLIFICATION THE CENTRAL PLAINS BEFORE DECOUPLING AND SWINGING NORTHEASTWARD THROUGH THE GREAT LAKES/NEW ENGLAND SUN AND MON RESPECTFULLY. THE ENSEMBLES CONTINUE TO SHOW A SLOWING TREND WITH INCREASED AMPLIFICATION TOWARD THE MOST AMPLIFIED EXAMPLE IN THE ECMWF SOLUTION. THOUGH THE 12Z GFS REMAINS SLIGHTLY FASTER AND LESS AMPLIFIED, IT IS TRENDING MORE SO THE THE ECMWF/SLOWING A BIT. THIS WAS ALSO SUPPORTED BY THE TREND IN THE 12Z NAM AS WELL. THE 00Z CMC/UKMET ARE ALSO GENERALLY SUPPORTIVE OVERALL. THIS PROVIDES ENOUGH SUPPORT TO SUGGEST A GENERAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z UKMET/ECMWF CONTINUED THE TREND OF A MORE SOUTHERN AMPLIFICATION TO THE WAVE CROSSING THE CENTRAL PLAINS...WHILE THE 12Z CMC IS A BIT FASTER AND FLATTER. STILL THE TIMING IS FAIR TO GOOD WITH THIS WAVE AND SENSIBLE WX SEEMS TO BE MATCHED WELL ENOUGH TO KEEP WITH THE INITIAL PREFERENCE. SHORTWAVE CROSSING SOUTHWEST CANADA TO THE NORTHERN ROCKIES AND THEN NORTHERN PLAINS BY MONDAY WITH SURFACE FRONTAL ZONE IN NORTHERN/CENTRAL PLAINS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/UKMET/ECMWF BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE POTENT SHORTWAVE CROSSING THE CENTRAL BC COAST TRAVERSES THE CANADIAN ROCKIES INTO THE CENTRAL PRAIRIES AND WILL ACT AS A DEEP FULCRUM UPPER LOW WITH RESPECT TO THE NEXT WAVE ENTERING THE PACIFIC NORTHWEST/VANCOUVER ISLAND FROM THE NORTH PACIFIC ON SUNDAY MORNING. THE TRENDS HAVE BEEN TOWARD A FLATTER SLIGHTLY SLOWER SOLUTION...THIS WAS BEST EXEMPLIFIED BY THE 12Z GFS WHICH TRENDED A BIT SLOWER AND WEAKER AS THE WAVE CROSSES THE NORTHERN US ROCKIES INTO THE CENTRAL PLAINS. THIS IS ALSO CLOSER TO THE 00Z ECMWF AND UKMET AS WELL AS THE 00Z ECENS MEAN AND 06Z GEFS MEAN PROVIDING A BIT MORE CONFIDENCE IN THE EVOLUTION. THE 12Z NAM IS FLATTER THAN OLDER RUNS OF THE NAM OR GFS BUT IS ALSO A BIT SLOWER CROSSING INTO THE PLAINS WHICH IS ALSO DENOTED IN THE SURFACE WX PATTERN. THOUGH THE 00Z CMC IS EVEN SLOWER THAN THE NAM MAKING IT A CLEAR OUTLIER. AS SUCH WILL PREFER A 12Z GFS AND 00Z UKMET/ECMWF BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: WHILE THE 12Z CMC TRENDED FASTER...IT REMAINS ON THE SLOW SIDE OF THE SUITE AND ALIGNS BETTER WITH THE LESSER PREFERRED TIMING OF THE 12Z NAM. THE 12Z ECMWF/UKMET BOTH TRENDED A LITTLE BIT SLOWER TRENDING IN THE NORTHERN STREAM ACROSS CENTRAL CANADA...LEADING TO A FURTHER SOUTHWARD SURFACE REFLECTION EXITING THE NORTH CENTRAL ROCKIES ALONG THE COLD FRONT OPPOSED TO THE DEEPER/FURTHER NORTH SOLUTION PRESENTED BY THE GFS. WILL KEEP INITIAL PREFERENCE OF GFS/UKMET/ECMWF BUT WEIGHT HIGHER TOWARD THE ECMWF/UKMET. LOW DEVELOPING OVER THE NORTHEAST PACIFIC AND MOVING TOWARDS VANCOUVER ISLAND 12Z MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHT ABOVE AVERAGE A CLOSED LOW FORMS OVER THE GULF OF ALASKA BY SUNDAY AND GIVEN DOWNSTREAM SLOWER SHORTWAVE...THIS WAVE HAS TRENDED A BIT FASTER OVERALL WITHIN THE ENSEMBLE SOLUTIONS WITH LESS SHORTWAVE RIDGING EXPECTED BETWEEN THE TWO SYSTEMS. THE 12Z UKMET IS A BIT DEEPER WITH THE WAVE AS IT CROSSES INTO THE PACIFIC NORTHWEST AT THE END OF DAY 3 BUT STILL IN ALIGNMENT WITH THE TIMING OF THE ENSEMBLES WHICH ARE SUPPORTED CLOSEST BY THE 12Z NAM/GFS AND 00Z ECMWF. THE 00Z CMC HAVING A THE SLOWEST DOWNSTREAM FEATURE LEADS TO CLOSER INTERACTION AND LEADS TO A DISTINCTLY DIFFERENT ORIENTATION OF THE WAVE MAKING IT APPEAR FASTER IN THE MASS FIELDS. ALL CONSIDERED WILL PREFER A NON-CMC SOLUTION FOR THIS SYSTEM AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: LITTLE CHANGE IN THE 12Z UKMET/ECMWF SOLUTIONS TO KEEP GOOD CONFIDENCE IN INITIAL THOUGHTS. THE 12Z CMC BEING SLIGHTLY FASTER DOWN STREAM SHOW SOME POSITIVE TRENDS TOWARD CONSENSUS BY THE END OF DAY 3 TO THIS SYSTEM BUT REMAINS FLATTER AND LESS FAVORABLY ORIENTED WITH THIS WAVE TO KEEP A NON-CMC BLEND AT THIS POINT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA