MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1121 AM EST THU DEC 01 2016 VALID DEC 01/1200 UTC THRU DEC 05/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHORTWAVE AMPLIFYING IN THE SOUTHWEST FRI WITH A CLOSED LOW FORMING AND ACROSS NORTHWEST MEXICO SAT SPURRING LEE SURFACE LOW ACROSS NEAR S TX/NE MEXICO BY MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/06Z GEFS/00Z UKMET BLEND CONFIDENCE: AVERAGE OVERALL TRENDS HAVE BEEN TOWARD A COMMON CONSENSUS YET THERE REMAINS A MODERATE TO HIGH SPREAD IN THE MODEL SOLUTIONS. THE 00Z ECMWF IS A STAND OUT WESTERN OUTLIER TO THE 00Z ECENS MEAN...DAY TO DAY ENSEMBLE SPAGHETTI ANALYSIS SHOWS PERSISTENT 12Z/00Z WAFFLING WITH THE ECENS MEAN AND GIVEN THE PROGRESSIVE STRONGER WESTERLY FLOW FURTHER NORTH IT APPEARS TO BE A BIT TOO PHASED GIVEN THE GENERAL CONSENSUS IN DEPTH OF LATITUDE THE CUT-OFF MAKES INTO MEXICO. WPC MEDIUM RANGE CONTINUES TO FAVOR A GFS/GEFS SOLUTION FOR THIS SYSTEM FOR THE LAST FEW DAYS AND SEE NO SIGNIFICANT REASON TO DEVIATE AT THIS TIME...THOUGH BEING A FAR WESTERN SOLUTION THE 00Z OPERATIONAL ECMWF MAY HAVE SOME UTILITY AT LOW WEIGHTING IN THE PREFERRED BLEND. THE 12Z NAM CONTINUES TO PRESENT A DEEP TROF WITH A TIGHT INNER CORE (THOUGH LESSENING WITH EACH RUN TOWARD THE GFS/ECWMF APPEARANCE)...YET IS IS ALSO QUITE FAST SHIFTING EASTWARD AND IS NOT WITHIN THE CURRENT PREFERENCE. THE 12Z GFS TRENDED A BIT WEAKER WITH THE SHORTWAVE ENERGY DIGGING OUT THE CLOSED SYSTEM. THIS RESULTS IN LESS OF DROP IN LATITUDE AND SLIGHTLY FASTER/EASTWARD SHIFT...WHICH WAS FIRST HINTED AT BY THE 00Z PARALLEL GFS SOLUTION (BOTH MATCHING QUITE WELL). THIS ALSO ALIGNS WITH THE SHIFT EASTWARD SEEN IN THE 00 UKMET...FOR GOOD ALIGNMENT OF THE TROF BY THE END OF DAY 3. AS SUCH WPC PREFERENCE IS A BLEND OF THE 12Z GFS/00Z UKMET AND 06Z GEFS SOLUTION. CONFIDENCE IS RISING BUT REMAINS ON THE LOWER SIDE OF AVERAGE GIVEN THE REMAINING SPREAD. GREAT LAKES/NORTHEAST COASTAL LOW AND ASSOCIATED FRONTS EXITING NORTHEAST THROUGH SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE 12Z NAM CONTINUES TO BE A BIT MORE AMPLIFIED BY SAT WITH THE INNER CORE AS IT SHIFTS EAST THROUGH NORTHEAST NEW ENGLAND ON SAT IN COMPARISON TO THE REST OF THE SUITE. STILL GIVEN THESE MINOR MASS DIFFERENCES EXIST THERE IS NO REASON TO SUGGEST ONE PARTICULAR SOLUTION OVER ANOTHER. AS SUCH A GENERAL MODEL BLEND SHOULD COVER THE UPPER LOW, SURFACE REFLECTIONS IN ONTARIO/QUEBEC AND COASTAL DEVELOPMENT IN NEW ENGLAND INCLUDING THEIR DEPTH/STRENGTH THROUGH THE REMAINING TIME AFFECTING THE CONUS. SHORTWAVE CROSSING SOUTHWEST CANADA FRI INTO SAT TRACKING ACROSS THE NORTHERN PLAINS TOWARD THE WESTERN GREAT LAKES BY SUNDAY NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z NAM/GFS AND 00Z UKMET BLEND CONFIDENCE: AVERAGE A STRONG 150+ KT JET STREAK APPROACHES AND REACHES VANCOUVER ISLAND ON SAT. THE WAVE DOWNSTREAM FROM THE JET MAX WILL BEGIN TO AMPLIFY ACROSS THE SOUTHERN CANADIAN/NORTHERN U.S. ROCKIES AND SUPPORT A WEAK SURFACE DEVELOPMENT IN THE LEE ACROSS SW SASKATCHEWAN BY SAT EVENING. THEREAFTER MODEL SPREAD INCREASES SLIGHTLY AS THE TROF AMPLIFIES AND COLLECTS ANY REMAINING ENERGY OF THE PRECEDING WAVE THAT SHEARED THE BULK OF ENERGY SOUTH AS IT SHIFTS INTO THE CENTRAL PLAINS. THE MORE ENERGY REMAINING PHASED WITH THE SOUTHERN STREAM LEADS TO DEEPER AMPLIFICATION OF THE WAVE AS A WHOLE CROSSING INTO THE WESTERN GREAT LAKES BY SUN NIGHT. THIS INCLUDES THE 00Z UKMET/CMC/ECMWF AND LESSER SO 12Z NAM/GFS. THE 12Z GFS DID TREND A BIT MORE AMPLIFIED THAN THE 00Z/06Z RUNS BUT REMAINS A BIT FASTER THAN THE 12Z NAM/00Z UKMET. THE 09Z SREF SEEMS MOST OUT OF PLACE OVERALL WITH THE TIMING AND SHAPE OF THE SOLUTION 70-90 DEGREES DIFFERENT WITH THE HEIGHT PACKING OVER THE OH VALLEY BY DAY 3. PREFERENCE TOWARD LESS INTERACTION WITH THE SOUTHERN STREAM CUT-OFF SEEMS MORE REASONABLE GIVEN DIFFERENCES THERE (SEE ABOVE). AS SUCH WILL PREFER THE 12Z GFS AND INCLUDE THE 12Z/00Z UKMET TO HEDGE SOME OF THE HIGHER AMPLIFIED SOLUTIONS PRESENTED IN THE ENSEMBLE SUITE. CONFIDENCE IS QUITE HIGH THROUGH EARLY SAT...BUT EVENTUALLY REDUCES TO AVERAGE BY SUN. SHORTWAVE TRACKING INTO NW WA/VANCOUVER ISLAND EARLY SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF/UKMET/CMC/ECENS MEAN AND 06Z GEFS MEAN CONFIDENCE: SLIGHTLY BELOW AVERAGE THE MODELS START TO BUCKLE THE WESTERLY ONSHORE FLOW WITH A LOW AMPLITUDE WAVE CROSSES THE NORTHEAST PACIFIC SUN PRECURSORY TO THE DEEPER WAVE/CLOSING OFF LOW DEVELOPING IN THE GULF OF AK. THE 12Z GFS FOLLOWED BY THE 12Z NAM ARE MORE AGGRESSIVE AND AMPLIFIED WITH THIS WAVE SUPPORTING A DEEP SURFACE CYCLONE LEE OF THE NORTHERN MT ROCKIES BY THE END OF DAY 3. THE 06Z GEFS DOES SUPPORT A DEEPER WAVE THAN THE FLATTER 00Z NON-NCEP MODELS AND ECENS MEAN...YET THERE APPEARS TO BE A MODERATE SPREAD IN THE GEFS SOLUTIONS TO SUGGEST THE 12Z GFS IS A BIT TOO AMPLIFIED AND FAST. AS SUCH WILL FAVOR THE MORE TEMPERED/SLOWER 00Z ECMWF/UKMET/CMC WITH INCLUSION OF THE 06Z GEFS IN THE PREFERENCE. CONFIDENCE IS SLIGHTLY BELOW AVERAGE GIVEN THE TIMING/AMPLITUDE OF THE WAVE ARE NOT WELL ESTABLISHED IN CONTINUITY WITH CONTINUED RUN TO RUN VARIABILITY EXPECTED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA