MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1239 PM EDT FRI JUL 11 2014 VALID JUL 11/1200 UTC THRU JUL 15/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ================================================== 12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES ================================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ================================================== ...DEEP CYCLONE AFFECTING THE CENTRAL AND NORTHERN U.S... PREFERENCE: BLEND OF 06Z GFS WITH 00Z ECMWF/CANADIAN THIS SYSTEM WILL DIG OVER THE MIDWEST AND GREAT LAKES THROUGH MONDAY...WHILE LEAD SHORTWAVE SPREAD HEIGHT FALLS TO NEW ENGLAND AND THE MID ATLANTIC...AND SURFACE HIGH PRESSURE BUILDS SOUTH THROUGH THE PLAINS. REGARDING 850 MB TEMPERATURES AND 500 MB HEIGHTS...AND RELATIVE TO CLIMATOLOGY...STANDARD DEVIATIONS ARE LIKELY TO REACH 2 TO 3 WITHIN THE RIDGE OVER WESTERN NORTH AMERICA AND MINUS 2 TO MINUS 3 WITHIN THE DOWNSTREAM TROUGH IN THE NORTHERN U.S. THE 12Z GFS JUMPED TOWARD A SOLUTION THAT IS QUITE A BIT FASTER AND NOT AS DEEP. THE SLOWER AND DEEPER ECMWF/CANADIAN SOLUTIONS HAD BEEN PREFERRED...BUT WE ALSO NOTE THAT THOSE SOLUTIONS FALL TOWARD THE DEEP EDGE OF THE RELATIVELY NARROW SPREAD FOR THIS SYSTEM. WITHOUT ANY STRONG EVIDENCE FOR A PARTICULARLY ROBUST SYSTEM...GIVEN THE TIME OF YEAR AND HIGH SUN ANGLE OVER THE COLD AIR SOURCE REGION...WE SUGGEST BLENDING THE DEEP ECMWF/CMC SOLUTIONS TOWARD SOMETHING A BIT MORE TAME. THE 06Z GFS SEEMS A VIABLE OPTION...AS IT FELL IN LINE WITH THE GEFS MEAN AND ECMWF ENSEMBLE MEAN. AT THE SURFACE THE 06Z GFS MAY BE SLIGHTLY SLOW TO DROP THE EFFECTIVE FRONTAL BOUNDARY THROUGH THE PLAINS. THE 12Z NAM LOOKS GOOD THROUGH DAY 3...AND COULD VERY NEARLY BE INCLUDED IN OUR DAY 1-3 PREFERENCE...BUT IT DOES JUMP SLIGHTLY AHEAD OF CONSENSUS LATE IN THE PERIOD. ...SYSTEM MOVING INTO THE PACIFIC NORTHWEST... PREFERENCE: BLEND OF THE OPERATIONAL MODELS...EXCLUDING THE 12Z NAM THE GLOBAL MODELS ARE NOW HANDLING THIS SHORTWAVE TROUGH SIMILARLY. THE 12Z NAM PRODUCED A UNIQUE SOLUTION BY SPLITTING THE ENERGY WITHIN THE BASE OF THIS SMALL FEATURE AND LEAVING A CYCLONIC MID LEVEL CIRCULATION EMBEDDED WITHIN RIDGING NEAR THE CA/OR COAST. SUCH AN OCCURRENCE WOULD NOT BE IMPOSSIBLE GIVEN POTENTIALLY WEAK INTERACTION BETWEEN THIS TROUGH AND THE WESTERLIES...BUT THERE IS LITTLE MODEL SUPPORT AT THE CURRENT TIME. SREF CLUSTERS LEND MORE SUPPORT TO THE GLOBAL MODEL CONSENSUS IN THIS CASE. ...WESTWARD MOVING INVERTED TROUGH INFLUENCING THE SOUTHWEST U.S... PREFERENCE: BLEND OF THE OPERATIONAL MODELS THE GUIDANCE IS IN GOOD AGREEMENT WITH THIS SYSTEM MOVING WEST NEAR THE U.S./MEXICO BORDER. WE HAVE NO STRONG PREFERENCE FOR ANY PARTICULAR MODEL SOLUTIONS...WITH ABOVE AVERAGE CONFIDENCE CONSIDERING THE MINIMAL MODEL SPREAD. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE