MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 116 AM EDT MON JUL 13 2015 VALID JUL 13/0000 UTC THRU JUL 16/1200 UTC ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH FORECAST PREFERENCES AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO IMPACT THEIR SHORT TERM FORECASTS. EAST COAST SURFACE LOW LIFTING TOWARD GEORGES BANK BY TUES MORNING. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z ECMWF/CMC AND 00Z NAM CONFIDENCE: ABOVE AVERAGE EXCELLENT RUN TO RUN CONSISTENCY OF THE ECMWF ALONG WITH AGREEMENT FROM THE 00Z NAM AND 12Z CMC AND 12Z ECMWF ENSEMBLE MEANS PROVIDE GOOD CONFIDENCE IN REMAINING LOCKED ON THIS SOLUTION. THE 12Z UKMET STILL REMAINS STRONG AND IS DISPLACED FROM THE BEST CLUSTERING. THE 00Z GFS REMAINS WEAK LIKE ITS PRIOR RUNS...ALSO NOT ADDED TO THE BLEND. SO 12Z ECMWF/CMC AND 00Z NAM BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE. UPPER LOW OVER S SASKATCHEWAN TRANSVERSING THE GREAT LAKES WED AND REINFORCING THE EASTERN U.S. TROF BEFORE SHIFTING EAST BY THURSDAY. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z GFS/NAM/12Z ECMWF CONFIDENCE: AVERAGE SUBTLE DIFFERENCES STILL EXIST WITH THE 00Z NAM/GFS/ECMWF. THE 00Z NAM IS THE STRONGEST IN LINE WITH KNOW BIAS...THE GFS IS STRONGER IN THE NORTHERN STREAM ACROSS NEW ENGLAND MAKING THE TROF A BIT FASTER THAN THE SLOWER AND FURTHER SOUTHWEST ECMWF. STILL THEY ARE IN REMARKABLY GOOD AGREEMENT WITH SUPPORT OF THE ENSEMBLES (21Z SREF/12Z ECMWF ENSEMBLE MEAN/18Z GEFS MEAN). WITH MEAN TIMING AND DEPTH OF THE EVOLUTION EVEN BY DAY 3 IN THE MID-ATLANTIC AND DESCENT CLUSTERING OF THE SURFACE INFLECTIONS ALONG THE FRONTAL ZONE SUPPORTS A 00Z NAM/GFS/12Z ECMWF BLEND WITH AVERAGE CONFIDENCE. THE 12Z UKMET A BIT WEAKER AND NORTH OF OTHER DETERMINISTIC MODELS AND THE 12Z CMC IS GOOD ALOFT BUT FAST/STRONG IN THE LOWER LEVELS PARTICULARLY WITH THE SURFACE LOW TO NOT BE INCLUDED IN THE BLEND AT THIS TIME. LEE-TROF ACROSS GREAT PLAINS IN RESPONSE TO UPSTREAM HEIGHT FALLS WED INTO THUR ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z NAM/GFS AND 12Z ECMWF/UKMET/CMC CONFIDENCE: AVERAGE BROAD SOUTHWESTERLY FLOW ACROSS THE ROCKIES DEVELOP A LEE TROF IN RESPONSE TO UPPER LEVEL TROF UPSTREAM SHIFTING OVER THE WESTERN ROCKIES BY WED. FAIRLY GOOD AGREEMENT EXISTS IN THE DEVELOPMENT OF SURFACE LOWS ACROSS KS/CO AND SD/MT/WY...IN RESPONSE TO WEAK SHORTWAVES OUT OF BASE OF THE TROF OVER NEW MEXICO AND ENERGY THROUGH THE MAIN NORTHERN STREAM RESPECTFULLY. FAIRLY GOOD AGREEMENT IS SEEN WITH THESE LOWS AND THE LOCATION OF CONVECTIVE COMPLEXES THAT DEVELOP...THOUGH MAGNITUDES IN QPF...AS EXPECTED ARE VARY. MASS FIELDS ARE NOT TOO DRAMATICALLY DIFFERENT THOUGH GIVEN UPSTREAM DIFFERENCES (SEE WEST COAST TROF SECTION BELOW) THE 00Z GFS IS A BIT SLOWER IN EJECTION OF ENERGY COMPARED TO OTHER DETERMINISTIC RUNS AND THE 18Z GEFS MEAN. GIVEN MOST DIFFERENCES ARE LIKELY IN THE MESOSCALE/STORM SCALE AND GENERALLY SMALL FOR DAY 3...A GENERAL OPERATIONAL MODEL BLEND IS PREFERRED AT AVERAGE CONFIDENCE AT THIS TIME. WEST COAST TROF SLIPS ONSHORE BY TUESDAY INCREASING POSITIVE TILT AS GULF OF ALASKA LOW SHIFTS OVER TO SOUTHWEST CANADA BY THE END OF THE FORECAST PERIOD. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN/18Z GEFS MEAN CONFIDENCE: AVERAGE WELL PROGGED MEAN TROF REMAINS IN VERY GOOD AGREEMENT AS IT BEGINS TO SLIP ASHORE. 12Z CMC DEPARTS FROM THE OTHER MODELS EARLIER AND IS DEEPER AND SLOWER IN THE BASE WHILE FLATTENING IN THE NORTHERN STREAM. THE 12Z UKMET IS THE FASTEST ACCOMPANIED BY THE 00Z NAM...THOUGH LESS SO. THE 00Z GFS REMAINS IN GOOD AGREEMENT WITH PRIOR RUNS THOUGH BY THE END OF THE FORECAST PERIOD IT STARTS TO BREAK AWAY FROM THE OTHER SOLUTIONS. THE EVOLUTION OF THE ENERGY OF THE UPPER LOW OVER SOUTHERN CANADA IS STRONGER AND FURTHER SOUTHWEST THAN OTHER MODEL GUIDANCE WITH SOME INFLUENCES FURTHER SOUTH INCREASING THE POSITIVE TILT TO THE TROF AS A WHOLE. THE 00Z GFS PRIOR TO DAY 3 COULD BE BLENDED INTO A PREFERENCE...BUT GIVEN THE DIFFERENCES ON DAY 3...WILL PREFER A BLEND OF THE 12Z ECMWF/12Z ECMWF MEAN AND THE 18Z GEFS MEAN TO CAPTURE THE PRIOR TRENDS AND KEEP WITH SOME BETTER RUN TO RUN CONTINUITY. THOUGH THIS IS A SLIGHT SHIFT IN PREFERENCE OVER A CONSISTENT BLEND OVER THE PAST DAY OR SO...OVERALL CONFIDENCE IN THE BLEND REMAINS AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA