MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1144 PM EST FRI JAN 08 2016 VALID JAN 09/0000 UTC THRU JAN 12/1200 UTC ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO DEGRADE THEIR SHORT RANGE FORECASTS. SHORTWAVE TROUGH REACHING THE N-CNTRL U.S. LATE ON MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM / 12Z ECMWF COMPROMISE CONFIDENCE: AVERAGE THE 00Z GFS LOOKS TO AMPLIFY SHORTWAVE ENERGY TOO FAR TO THE SOUTH ACROSS THE UPPER MIDWEST MON NIGHT...WITH THE NAM/ECMWF BETTER MATCHING THE ENSEMBLES. BOTH THE 12Z UKMET/CMC ARE SLOWER/LESS AMPLIFIED WITH THIS WAVE AND ARE NOT PREFERRED. UPPER TROUGH AXIS NEARING THE WEST COAST MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF COMPROMISE CONFIDENCE: AVERAGE THERE ARE DIFFERENCES WITH HOW AN UPPER TROUGH AXIS EVOLVES AS IT NEARS THE WEST COAST MON MORNING WHILE ENCOUNTERING A WEST COAST RIDGE. THE MORE SRN NAM WANTS TO TAKE THE BULK OF THE VORT ENERGY INTO NRN CALIFORNIA WHILE THE 12Z ECMWF TAKES THE ENERGY TO THE NORTH TOWARD THE COASTS OF WASHINGTON/OREGON. THE 12Z CMC MATCHES THE NAM TO SOME DEGREE AND OVERALL TRENDS IN THE DETERMINISTIC GUIDANCE HAVE BEEN INCONSISTENT. STILL...THE ENSEMBLE MEANS SEEM TO SUPPORT A GFS/ECMWF BLEND THE CLOSEST...WITH THE ACTUAL EVOLUTION LIKELY TO GO SOMEWHERE IN THE MIDDLE OF THE TWO MODEL IDEAS. ELONGATED UPPER TROUGH AXIS REACHING THE WEST COAST THIS MORNING SUBSEQUENT SHORTWAVE ENERGY DIVING THROUGH THE SOUTHWEST ON SUN AND THE SRN PLAINS MON EVENING/NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS...12Z ECMWF...12Z CMC COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE GFS HAS HELD THE BEST CONTINUITY WITH THIS FEATURE THROUGH ITS 00Z/09 RUN...AND IT MATCHED SIMILARLY BY THE 12Z ECMWF WHICH HAS ADJUSTED TOWARD THE GFS OVER ITS PAST 3 RUNS. THE GFS/ECMWF/CMC COMBO MATCHES BEST TO THE ENSEMBLE MEANS...WHILE THE 00Z NAM IS ON THE SLOW SIDE AND THE 12Z UKMET A BIT MORE AMPLIFIED THAN THE CONSENSUS. SHORTWAVE PASSING ACROSS THE LOWER MISSISSIPPI VALLEY LATER TODAY SURFACE LOW TRACKING ACROSS THE OHIO VALLEY SAT NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE WHILE A MODEST ENSEMBLE SPREAD STILL EXISTS...THE 12Z UKMET IS STILL ON THE DEEPER EDGE OF THE GUIDANCE WITH THE MID-LEVEL AND SURFACE LOW...AND THE 00Z NAM IS ON THE WEAK SIDE...WITH THE NAM ALSO BECOMING A BIT MORE PROGRESSIVE ALOFT BY SAT NIGHT/SUN MORNING. THE SURFACE LOW IN THE 12Z CMC IS ON THE FAR WRN EDGE OF THE ENSEMBLE SCATTER LOW PLOTS...AND HAS BEEN FOR THE PAST SEVERAL RUNS...WITH THE BETTER ENSEMBLE CLUSTERING LYING NEAR THE 00Z GFS AND 12Z ECMWF. THE GFS/ECMWF HAVE CONVERGED TOWARD ONE ANOTHER EVER SO SLIGHTLY OVER THE PAST FEW 12/00Z CYCLES...AND NOW REPRESENT THE BEST COMPROMISE OF THE DETERMINISTIC GUIDANCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO