MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 141 AM EST SAT JAN 24 2015 VALID JAN 24/0000 UTC THRU JAN 27/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SHORTWAVE/SURFACE LOW REACHING THE UPPER MISS VALLEY EARLY MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM / 00Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE A WESTERN RIDGE ALOFT CONTINUES TO SUPPORT MORE AMPLIFICATION OF A DOWNSTREAM TROUGH INTO THE N-CNTRL U.S. AND MIDWEST. IT APPEARS THE 00Z GFS/UKMET ARE TOO FLAT AND NORTH WITH A CORRESPONDING SURFACE LOW IN THE VICINITY OF THE UPPER MISSISSIPPI VALLEY MON NIGHT. THE NAM/ECMWF ARE THE TWO MOST REPRESENTATIVE MODELS OF WHAT IS EXPECTED TO OCCUR. CONFIDENCE IS REDUCED GIVEN A SIZABLE ENSEMBLE SPREAD CURRENTLY IN PLACE BY TUE MORNING. SHORTWAVE REACHING THE MID-MISSISSIPPI VALLEY ON SUN ALONG WITH THE ACCOMPANYING SURFACE LOW ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF BLEND CONFIDENCE: AVERAGE MODEL TRENDS HAVE BEEN DEEPER/SOUTH WITH THE SHORTWAVE TROUGH AND ACCOMPANY SURFACE LOW REACHING THE OHIO VALLEY SUN EVENING COMPARED TO YESTERDAY. THE 00Z GFS AND 12Z ECMWF ARE THE MOST REPRESENTATIVE MODELS WITH RESPECT TO THE ENSEMBLE MEANS AND TRENDS. THE REMAINING MODEL CONSENSUS IS ON EITHER SIDE OF THE RELATIVE AGREEMENT BETWEEN THE GFS AND ECMWF. THE NEW 00Z ECMWF IS ON THE EDGE OF THE LATEST ENSEMBLE SPREAD AND IS AN OUTLIER WITH RESPECT TO THE REMAINING 00Z DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE WITH THE SURFACE LOW AS IT MOVES INTO THE WRN ATLATNIC. CLOSED LOW FORMING NEAR BAJA CALIFORNIA THIS WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z GFS COMPROMISE CONFIDENCE: AVERAGE THE GUIDANCE IS IN RELATIVELY GOOD AGREEMENT WITH THIS SYSTEM UNTIL MONDAY NIGHT WHEN DIFFERENCES IN THE POSITION OF THE MID-LEVEL CLOSED LOW DEVELOP.THE ENSEMBLES AND TRENDS SUPPORT SOMETHING MORE TOWARD THE EAST...AWAY FROM THE 00Z GFS. DEEPENING SURFACE LOW TRACKING UP THE EAST COAST TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z NAM COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z NAM REMAINS ON THE FASTER SIDE OF THE GUIDANCE...BUT ALL OF THE DETERMINISTIC MODELS...INCLUDING THE NAM...HAVE BEEN CONSISTENT IN POSITION THROUGH SAT. THE TIGHTLY CLUSTERED ENSEMBLE LOW PLOTS SUPPORT A NON-NAM COMPROMISE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO