MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1215 AM EST SUN JAN 10 2016 VALID JAN 10/0000 UTC THRU JAN 13/1200 UTC ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION ALONG WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. SHORTWAVE LIFTING INTO THE NORTHEAST LATER TODAY DEEPENING SURFACE LOW MOVING INTO SERN CANADA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE ENSEMBLE LOW PLOTS HAVE BEEN RATHER CONSISTENT WITH ONLY SMALL DIFFERENCES AMONG THE LATEST DETERMINISTIC GUIDANCE. A GENERAL MODEL COMPROMISE WILL SUFFICE FOR THIS SYSTEM. SHORTWAVE/SURFACE LOW AFFECTING THE GREAT LAKES MON/TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THERE ARE RELATIVELY MINOR DIFFERENCES WITH THIS SYSTEM...MAINLY WITH TIMING AS THE 00Z NAM...12Z UKMET/CMC ARE A BIT SLOWER/MORE AMPLIFIED WHILE THE 00Z GFS AND 12Z ECMWF ARE A BIT AHEAD REGARDING THE UPPER TROUGH PROGRESSION. REGARDING THE SURFACE LOW...ENSEMBLE LOW CLUSTERING IS RATHER TIGHT THROUGH TUE...AND FAVORS A GENERAL MODEL COMPROMISE. MID-LEVEL SHORTWAVE TRACKING ACROSS THE SOUTHWEST SUN NIGHT AND INTO THE SRN PLAINS MON NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE ENSEMBLE SPAGHETTI PLOTS SHOW THE ECMWF/ECMWF MEAN HELD BACK OVER TEXAS WHILE THE REMAINING ENSEMBLE MEMBERS ARE A BIT AHEAD OF THE ECMWF. THIS HAS BEEN A CONSISTENT PATTERN FOR THE PAST 2 RUNS OF ENSEMBLES...AND THE LATEST DETERMINISTIC GUIDANCE IS WITHIN THE ENSEMBLE SPREAD FROM FASTER TO SLOWER. GIVEN THE DIFFERENCES ARE RATHER SMALL...WILL GO WITH A GENERAL MODEL COMPROMISE OF THE FASTER/SLOWER SOLUTIONS. SPLIT FLOW AFFECTING THE WEST COAST BY EARLY NEXT WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM / 12Z ECMWF COMPROMISE CONFIDENCE: AVERAGE ONLY THE 12Z CMC DIFFERS FROM THE REMAINING GUIDANCE WITH TAKING VORT ENERGY ON A MORE SRN TRACK INTO NEVADA TUE MORNING...AS OTHER GUIDANCE THAT WAS SOUTH HAS ADJUSTED NORTH TOWARD THE ECMWF IDEA FROM YESTERDAY. THE 00Z GFS IS ALMOST OUTSIDE OF THE LATEST SPAGHETTI HEIGHTS WITH TIMING THOUGH ACROSS THE PACIFIC NORTHWEST...SO A NAM/ECMWF COMPROMISE WILL BE PREFERRED. HOWEVER...IMPACT DIFFERENCES MAY BE MINIMAL WITH THE SLIGHTLY FASTER GFS. PACIFIC COLD FRONT NEARING THE PACIFIC NORTHWEST EARLY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 99Z NAM...00Z GFS..12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THE LATEST DETERMINISTIC GUIDANCE SHOWS THE IDEA OF TWO PIECES TO AN UPPER TROUGH FORECAST TO NEAR THE WEST COAST MID-WEEK. THE 12Z CMC IS UNIQUE HOWEVER...WITH A WEAKER SRN PORTION AND WITH DOWNSTREAM RIDGING ACROSS THE NRN ROCKIES BY WED MORNING. WHILE THE 00Z NAM AND 12Z ECMWF ARE THE MOST SIMILAR...THE 00Z GFS CANNOT BE RULED OUT WITH A SLIGHTLY QUICKER NRN STREAM TIMING. A BLEND OF THE NAM/GFS/ECMWF IS PREFERRED...BUT WITH SLIGHTLY BELOW AVERAGE CONFIDENCE GIVEN THE LONGER TIME RANGE IN THE FORECAST AND TIMING SPREAD SEEN IN THE ENSEMBLES. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO