MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 216 PM EST TUE MAR 08 2016 VALID MAR 08/1200 UTC THRU MAR 12/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z FINAL MODEL EVALUATION AND PREFERENCES ...WAVE/SURFACE LOW OVER MN...MOVING NORTH OF NEW ENGLAND WEDNESDAY... PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE WAVE AND SURFACE LOW TRACK...HOWEVER DO NOTE SOME DIFFERENCES IN THE LOCATION OF THE WARM FRONTAL BOUNDARY...WHICH DOES HAVE A QPF IMPACT. 12Z GFS SEEMS TOO FAR SOUTH...WITH THE 0Z ECMWF TOO FAR NORTH. SOMETHING IN BETWEEN...CLOSER TO A 12Z NAM AND 0Z GEM/UKMET MAY BE BEST. ALSO COULD TAKE A SOLUTION BETWEEN THE 12Z GFS AND 0Z ECMWF. 19Z UPDATE: 12Z GUIDANCE IS IN GOOD AGREEMENT WITH THE WAVE AND LOW TRACK. THE 12Z GFS SEEMS A BIT TOO FAR SOUTH/SLOW WITH THE WARM FRONTAL PROGRESSION ACROSS NORTHERN NEW ENGLAND. ...SHORTWAVE TROUGH TRAVERSING THE NORTHERN TIER TUES-THURS... ...SURFACE LOW DEVELOPING OVER THE MIDWEST AND TRAVERSING THE NORTHEAST INTO THURSDAY... PREFERENCE: BLEND OF THE 12Z GFS/ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 06Z AND 12Z GFS HAVE TRENDED QUICKER WITH THIS SHORTWAVE AND ASSOCIATED SURFACE LOW CLOSER TO THE 0Z ECMWF SOLUTION. THE 12Z NAM AND 0Z GEM/UKMET REMAIN SLOWER. THIS IS A SIGNIFICANT DIFFERENCE...AS HOW THIS WAVE AND FRONT INTERACTS WITH THE SOUTHERN CLOSED UPPER LOW AND MOISTURE PLUME WILL HAVE A SIGNIFICANT IMPACT IN THE QPF AXIS AND TIMING FROM PORTIONS OF THE MID MS VALLEY INTO THE OH VALLEY AND SURROUNDING AREAS. THE 06Z GEFS MEAN AND 0Z ECMWF MEAN ARE SLOWER THAN THEIR DETERMINISTIC RUNS. HOWEVER AT TIMES THE ENSEMBLE MEANS CAN LAG THE DETERMINISTIC RUNS IN THE SHORT TERM PERIOD WHEN FEATURES START TO BECOME BETTER RESOLVED. THUS FOR NOW WOULD TREND THE FORECAST TOWARDS A QUICKER 12Z GFS AND 0Z ECMWF BLEND WITH THIS FEATURE...ALTHOUGH POSSIBLY INCORPORATING SOME OF THE 12Z NAM (WHICH BETTER MATCHES THE GEFS/ECMWF MEANS) IN CASE THE DETERMINISTIC GFS/ECMWF HAVE TRENDED TOO MUCH IN THE QUICKER DIRECTION. 19Z UPDATE: THE QUICKER TREND HAS CONTINUED...PUSHING THE MOISTURE AXIS ASSOCIATED WITH THE ATMOSPHERIC RIVER FURTHER SOUTHEAST. THUS WILL NOW GO AHEAD AND REMOVE THE 12Z NAM FROM OUR PREFERRED BLEND...AS IT IS THE SLOWEST AND FURTHEST NORTHWEST SOLUTION. SOME DIFFERENCES ON HOW FAR NORTH/SOUTH THE WAVE TRACKS AS WELL...WITH THE NEW 12Z ECMWF FURTHER SOUTH THAN THE 12Z GFS. THE 12Z GEM/UKMET ARE IN THE SAME BALLPARK AS THE ECMWF/GFS...BUT FOR SIMPLICITY A BLEND OF THE 12Z ECMWF/GFS PROBABLY WORKS AS A STARTING POINT FOR HANDLING THIS SYSTEM. ...UPPER TROUGH/CLOSED LOW AMPLIFYING OVER THE SOUTHWEST... ...DEEP CLOSED LOW CROSSING NORTHERN MEXICO TUES/WED... PREFERENCE: 12Z GFS/ECMWF/UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS ARE FINALLY COMING INTO BETTER AGREEMENT WITH THIS SYSTEM...COMPROMISING BETWEEN WHAT HAD BEEN A ECMWF SOUTEHRN AND SLOW SOLUTION AND A GFS NORTH AND QUICK SOLUTION. THE 12Z GFS CONTINUED THIS TREND AND IS NOW VERY CLOSE TO THE 0Z ECMWF ENSEMBLE MEAN SOLUTION. THE 0Z ECMWF IS A BIT SLOWER/SOUTH OF ITS MEAN...AND WOULD NOT BE SURPRISED TO SEE THE 12Z TREND IN LINE WITH ITS ENSEMBLE MEAN AND THE GFS. BUT DIFFERENCES ARE OVERALL SMALL ENOUGH THAT THE 0Z ECMWF COULD STILL BE USED IN ANY BLEND. THE 12Z NAM IS NOW ALONE IN ITS FURTHER NORTH AND QUICK SOLUTION ND IS CONSIDERED A LESS LIKELY SOLUTION. THE 0Z GEM SEEMS OKAY WITH ITS POSITION...BUT SEEMS TOO STRONG WITH THE UPEPR LOW. 19Z UPDATE: THE 12Z ECMWF DID NOT SIGNIFICANTLY CHANGE FROM ITS PREVIOUS RUNS...BUT WHERE IT DID IT IS NOW CLOSER TO THE 12Z GFS. THUS A CONTINUED ECMWF/GFS BLEND WORKS WELL WITH THIS SYSTEM. THE 12Z UKMET IS PRETTY SIMILAR TO THE GFS AND CAN THUS ALSO BE INCLUDED. THINK THE 12Z GEM MAY BE TOO PROGRESSIVE. ...SHORTWAVE TROUGH/FRONT IMPACTING NORTHWEST THROUGH THURSDAY... PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE DIFFERENCES IN THE MODELS WITH THIS SYSTEM APPEAR RELATIVELY MINOR AND THUS WILL PREFER A GENERAL MODEL BLEND AT THIS TIME. ...UPPER TROUGH/SURFACE LOW APPROACHING THE WEST COAST ON FRI... PREFERENCE: 12Z GFS/ECMWF/GEM BLEND CONFIDENCE: AVERAGE THE MODELS SHOW A ROBUST UPPER TROUGH AND ASSOCIATED SURFACE LOW APPROACHING THE WEST COAST BY EARLY FRI ALONG WITH AN ATTENDANT FRONTAL ZONE. THE 12Z NAM IS AN OUTLIER IN HOW IT HANDLES THIS SYSTEM...FOCUSING MORE OF THE SHORTWAVE ENERGY FURTHER SOUTH WITHIN THE TROUGH THAN THE CONSENSUS. THE 12Z GFS PROBABLY MATCHES THE 06Z GEFS MEAN AND 0Z ECMWF MEAN THE BEST...WITH THE 0Z ECMWF A BIT QUICKER AND FURTHER NORTH WITH THE WAVE ENERGY. THE 0Z UKMET IS CLOSER TO THE 12Z GFS SOLUTION...JUST PROBABLY A BIT TOO QUICK. SO WHILE WOULD LEAN TOWARDS A 12Z GFS SOLUTION...A BLEND OF THE 12Z GFS AND THE 0Z ECMWF/UKMET SHOULD GIVEN A DECENT SOLUTION AT THIS TIME. THE 0Z GEM APPEARS TOO SLOW WITH THIS SYSTEM. 19Z UPDATE: THE 12Z VERSIONS OF THE GFS/ECMWF/GEM ARE IN GOOD AGREEMENT WITH THIS SYSTEM AND CLOSEST TO ENSEMBLE MEANS. THE 12Z UKMET IS LIKELY A TAD TOO FAST. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD