MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1205 AM EST SUN FEB 19 2017 VALID FEB 19/0000 UTC THRU FEB 22/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE/COLD FRONT CROSSING THE NORTHEAST THROUGH SUN... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. ...DEEPENING TROUGH/CLOSED LOW DEVELOPMENT NEAR NORTHERN NEW ENGLAND/NOVA SCOTIA... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE IN THE WAKE OF THE SHORTWAVE CROSSING THE NORTHEAST DURING THE DAY SUN...THE MODELS ADVERTISE AN AMPLIFYING TROUGH NEAR NORTHERN NEW ENGLAND BY SUN NIGHT...WITH A CLOSED LOW DEVELOPING OVER THE NOVA SCOTIA ON MON. THE MODELS ARE IN GOOD AGREEMENT THIS AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED. ...SHORTWAVE/SURFACE LOW APPROACHING THE PACIFIC NORTHWEST ON SUN... ...UPPER TROUGH EJECTING OUT OF THE SOUTHWEST THROUGH SUN... ...CONSOLIDATING ENERGY EJECTING OUT ACROSS THE PLAINS/MIDWEST... ...SURFACE LOW PRESSURE/COLD FRONT CROSSING THE PLAINS/MIDWEST... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z UKMET CONFIDENCE: AVERAGE...BECOMING BELOW AVERAGE A NORTHERN STREAM TROUGH AND ASSOCIATED SURFACE LOW WILL APPROACH THE PACIFIC NORTHWEST ON SUN...WITH THE ENERGY THEN QUICKLY TRAVERSING THE NORTHERN ROCKIES AND NORTHERN PLAINS THROUGH MON. THIS ENERGY WILL BE RESULTING IN LEE-SIDE CYCLOGENESIS ACROSS THE HIGH PLAINS BY LATER SUN. MEANWHILE...THESE HEIGHT FALLS WILL HELP TO KICK A PORTION OF THE SOUTHERN STREAM TROUGH/CLOSED LOW OUT OF THE SOUTHWEST AND NORTHEASTWARD ACROSS THE CENTRAL PLAINS AND THE MIDWEST THROUGH MON AND TUES. SOME PARTIAL PHASING WILL ALLOW DEEPENING LOW PRESSURE UP ACROSS THE NORTHERN PLAINS...WITH A TRAILING COLD FRONT EXTENDING SOUTH ACROSS THE CENTRAL PLAINS. ALL OF THIS ENERGY QUICKLY MOVES NORTHEAST ACROSS THE MIDWEST AND GREAT LAKES THROUGH TUES. THE 12Z CMC IS A PROGRESSIVE OUTLIER SOLUTION WITH THE NORTHERN STREAM ENERGY COMPARED TO AN OTHERWISE WELL-CLUSTERED MODEL SUITE. HOWEVER...WITH THE SOUTHERN STREAM ENERGY EJECTING OUT...THE 00Z GFS AND 12Z UKMET BECOME THE MOST PROGRESSIVE SOLUTIONS...WITH THE 00Z NAM/12Z CMC AND 12Z ECMWF ALL A BIT SLOWER. THE GFS DID TREND A BIT MORE PROGRESSIVE IN EJECTING THIS ENERGY NORTHEASTWARD. THERE IS GOOD MODEL CLUSTERING WITH THE SURFACE LOW PRESSURE EVOLUTION BETWEEN THE 00Z GFS/12Z UKMET AND 12Z ECMWF...BUT THEN THE DIFFERENCES BECOME FOCUSED ON THE COLD FRONT IN WHICH THE ECMWF LAGS THE GFS/UKMET WITH TIME. THE NAM AND CMC ARE SLOW WITH THE FRONT LIKE THE ECMWF AS IT CROSSES THE MIDWEST THROUGH TUES. CONFIDENCE BECOMES LIMITED IN TIME...BUT WILL LEAN TOWARD A BLEND OF THE GFS AND UKMET AT THIS TIME ACCOMMODATING THE LATEST TRENDS AND OVERLAPPING AGREEMENT WITH NORTHERN AND SOUTHERN STREAM ENERGY. MUCH OF THE UNCERTAINTY AGAIN IS CENTERED ON THE FRONTAL TIMING ACROSS THE MIDWEST. ...UPPER TROUGH TRACKING ACROSS THE SOUTHEAST ON SUN... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE ONLY MINOR DIFFERENCES REMAIN AT THIS POINT WITH THE SYSTEM. A GENERAL MODEL COMPROMISE CAN BE USED HERE. ...SHORTWAVE/SURFACE LOW APPROACHING THE WEST COAST ON MON... PREFERENCE: BLEND OF THE 12Z UKMET AND 12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE AS A BROADER UPPER TROUGH EVOLVES OFF THE WEST COAST...THE GUIDANCE SHOWS THE NEXT IN A SERIES OF SHORTWAVE IMPULSES AND ACCOMPANIES SURFACE LOWS APPROACHING THE WEST COAST BY EARLY MON. THE 00Z NAM IS A BIT SLOW WITH THIS IMPULSE BUT ALSO FAIRLY SHEARED WHICH RESULTS IN A WEAKER SURFACE REFLECTION COMPARED TO THE MODEL CONSENSUS. THE 12Z CMC IS BY FAR THE MOST PROGRESSIVE SOLUTION. THE 00Z GFS AGAIN IS THE STRONGEST SOLUTION AND IS THE MOST INTENSE WITH ITS SURFACE LOW. MEANWHILE...THE 12Z UKMET AND 12Z ECMWF ARE CLUSTERED TOGETHER ON A SOMEWHAT FLATTER SOLUTION RELATIVE TO THE GFS...WITH A WAVE TRACK A TAD SOUTH OF THE UKMET/ECMWF CAMP. WILL FAVOR THE UKMET/ECMWF CAMP WHICH HAS ALSO BEEN RATHER CONSISTENT WITH THIS IMPULSE. ...SHORTWAVE/SURFACE LOW APPROACHING THE WEST COAST MON NIGHT... PREFERENCE: BLEND OF THE 12Z UKMET AND 12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE YET ANOTHER SHORTWAVE AND ASSOCIATED SURFACE LOW WILL APPROACH THE WEST COAST MON NIGHT ALONG WITH A COLD FRONT THAT WILL MOVE INLAND. THE 00Z GFS IS THE MOST PROGRESSIVE WITH THIS SYSTEM...WITH THE 12Z CMC THE SLOWEST AND DEEPEST. THE 00Z NAM...12Z UKMET AND 12Z ECMWF ARE IN BETWEEN SOLUTIONS...BUT THERE IS BETTER AGREEMENT WITH THE UKMET AND ECMWF...AND SINCE THEY ARE CLOSE TO THE MODEL CONSENSUS...A UKMET/ECMWF BLEND WILL BE PREFERRED. ...LONGWAVE TROUGH FINALLY REACHING THE WEST COAST BY WED... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THE LONGWAVE TROUGH EVOLVING OFF THE WEST COAST FINALLY BEGINS TO MOVE ASHORE BY WED ALONG THE WEST COAST. BY THAT TIME...THERE IS GENERALLY BETTER AGREEMENT/CLUSTERING WITH THE 00Z GFS AND 12Z ECMWF. THE 12Z UKMET APPEARS TOO STRONG/SLOW WITH ITS NEXT SURFACE LOW...AND THE 00Z NAM/12Z AND 12Z UKMET ALL SEEM TO HAVE POSSIBLY A LITTLE TOO MUCH ENERGY DIGGING IN THE BASE OF THE TROUGH. ...SOUTHERN STREAM TROUGH/CLOSED LOW DEVELOPMENT NEAR THE WESTERN GULF COAST... PREFERENCE: BLEND OF THE 00Z GFS/18Z GEFS MEAN AND THE 12Z ECENS MEAN CONFIDENCE: SLIGHTLY BELOW AVERAGE ENERGY IN THE BASE OF THE UPPER TROUGH/CLOSED LOW CURRENTLY IMPACTING THE SOUTHWEST THAT EJECTS OUT ACROSS THE PLAINS THROUGH SUN AND MON WILL SEPARATE OUT AND LEAD TO A NEW SOUTHERN STREAM TROUGH AND POSSIBLE CLOSED LOW OVER EASTERN TX AND THE ADJACENT LOWER MS VALLEY BY TUES. DIFFERENCES IN THE EVOLUTION OF THIS TROUGH ARE DEPENDENT ON HOW THE ENERGY NORTH ACROSS THE MIDWEST EVOLVES...DESCRIBED ABOVE WITH LOWER THAN AVERAGE CONFIDENCE. THE 12Z ECMWF IS THE STRONGEST SOLUTION WITH THE CLOSED LOW DEVELOPMENT...WITH THE 12Z CMC THE WEAKEST. THE 00Z GFS IS VERY CLOSE TO THE 12Z ECMWF...EXCEPT IS A BIT WEAKER. THE 12Z UKMET TENDS TO DIG MORE ENERGY A BIT FARTHER SOUTH AND IS A BIT SLOWER IN TIME VERSUS THE GFS AND ECMWF. THE LATEST GEFS MEAN AND ECENS MEAN ARE WELL CLUSTERED AND BOTH TEND TO FAVOR THE GFS MORE SO THAN THE ECMWF. WILL LEAN TOWARD A CONSENSUS OF THE GFS/GEFS MEAN AND ECENS MEAN AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON