MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 302 AM EDT THU JUL 09 2015 VALID JUL 09/0000 UTC THRU JUL 12/1200 UTC ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INITIALIZATION ERRORS DO NOT APPEAR TO DEGRADE THEIR SHORT TERM FORECASTS. UPPER LOW OVER NORTHERN CALIFORNIA SHIFTS INTO THE GREAT BASIN THROUGH FRIDAY BEFORE SHEARING OUT AND LIFTING NORTH INTO MONTANA BY SUNDAY... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z GFS/ECWMF AND 18Z GEFS MEAN/12Z ECMWF ENSEMBLE MEAN CONFIDENCE: SLIGHTLY BELOW AVERAGE A BROAD UPPER OVER CENTRAL CALIFORNIA WITH AN ELONGATED SHEAR AXIS WITH DIFFLUENT FLOW ACROSS THE GREAT BASIN INTO CENTRAL ROCKIES. AS THE WESTERN PORTION OF THE LOW SWINGS AROUND THE BASE ON FRIDAY INTO SATURDAY...A BULK OF THE LOWS ENERGY IS SHEARED INTO THE BROAD SOUTHWESTERLY FLOW ACROSS THE ROCKIES INTO THE PLAINS...WITH DETAILS PLEASE SEE BELOW. AS SUCH THE LOW EVOLVES INTO AN OPEN WAVE ACROSS THE GREAT BASIN WITH REMAINING ENERGY/VORTICITY LOBES LIFTING INTO THE NORTHWESTERN HIGH PLAINS OF MONTANA BY SUNDAY. SOME BETTER AGREEMENT IS STARTING TO TAKE PLACE AS THE 00Z ECMWF HAS COME INTO GOOD AGREEMENT WITH THE 00Z GFS IN TIMING/PLACEMENT AND STRENGTH WITH REGARD TO THE MAIN VORTICITY CENTER OF THE UPPER LOW. THE 00Z NAM IS ALSO IN GOOD TIMING/PLACEMENT BUT REMAINS A BIT STRONGER AND DEEPER TOWARD THE SOUTHEAST. THE 00Z CMC IS ALSO A BIT STRONG BUT PLACEMENT IS MUCH FURTHER SOUTH AND EAST THAN THE OTHERS...MAKING IT AN OUTLIER. THE 00Z UKMET SHEARS THE ENERGY OUT SO MUCH TO BARELY RESOLVE A WEAK VORT ACROSS MONTANA BY SUNDAY. WITH ALL THIS CONSIDERED...THE PREFERENCE IS GEARED TO THE 00Z GFS/ECMWF BLEND WITH A GOOD AMOUNT OF WEIGHTING STILL TO THE ENSEMBLE MEANS GIVEN THE HIGH SPREAD. WITH SOME BETTER AGREEMENT CONFIDENCE IS RAISED TO SLIGHTLY BELOW AVERAGE. DEEP UPPER TROF SETTLING INTO THE PACIFIC NORTHWEST BY THE WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 18Z GEFS/21Z SREF/12Z ECMWF ENSEMBLE MEANS CONFIDENCE: AVERAGE WITH THE LIFTING OUT OF THE UPPER LOW ACROSS CALIFORNIA ON DAY 1...THE TRAIN OF PACIFIC SHORTWAVES BEGIN TO AMPLIFY A WEST COAST TROF JUST OFFSHORE OF BRITISH COLUMBIA TO THE CENTRAL CALIFORNIA COAST BY SUNDAY. THOUGH THE TROF IS BROADLY HANDLED WELL BY THE DETERMINISTIC MODELS...THE FREQUENCY OF SHORTWAVES CONTINUES TO LEAD TO TIMING AND AMPLITUDE DIFFERENCES THAT NO ONE SPECIFIC MODEL IS CONSISTENT OR RELIABLE ALONE. AS SUCH A SOLUTION TOWARD THE MEAN...BEST REFLECTED BY THE 18Z GEFS/21Z SREF AND 12Z ECMWF ENSEMBLE MEANS...IS PREFERRED AT THIS TIME WITH AVERAGE CONFIDENCE. SHEAR AXIS/SHORTWAVE OF UPPER LOW EJECTING OUT OF COLORADO ROCKIES ACROSS THE PLAINS TO OHIO RIVER VALLEY FROM FRIDAY THROUGH SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND WITH HEAVY WEIGHTING TOWARD 18Z GEFS MEAN/12Z ECMWF ENSEMBLE MEAN CONFIDENCE: BELOW AVERAGE BROAD SOUTHWESTERLY FLOW ACROSS THE ROCKIES IS GENERALLY LIFTING NORTH AS A SOUTHEAST U.S RIDGE IS TAKING SHAPE AS IT BUILDS WEST INTO THE SOUTHERN GREAT PLAINS. ON FRIDAY MODELS AGREE THAT ENERGY FROM THE EASTERN PORTION OF THE UPPER LOW AS AN ELONGATED SHEAR AXIS WITHIN THE DIFFLUENT FLOW WILL EJECT OUT OF COLORADO INTO THE CENTRAL PLAINS. THE STRENGTH/CONSOLIDATION OF THIS VORTICITY AXIS APPEARS TO BE HIGHLY TIED TO CONVECTIVE PROCESSES LEADING TO SOME SIGNIFICANT DIFFERENCES. THE 00Z NAM IS THE STRONGEST THROUGHOUT THE LENGTH OF THE SHEAR AXIS AND BECOMES THE FASTEST FURTHER NORTH AND WEST. THE 00Z CMC IS MUCH TOO CONSOLIDATED WITH A STRONG VORT CENTER EJECTING OUT OF THE FOUR CORNERS AND PULLING THE ENERGY ASSOCIATED WITH THE UPPER LOW EASTWARD IN SIGNIFICANT DIFFERENCE TO NEARLY ALL OTHER GUIDANCE. THE 00Z UKMET PUTS MUCH OF THE SHEAR AXIS ENERGY FURTHER EAST AND AS SUCH IS VERY FAST...BUT ALSO VERY WEAK FURTHER WEST. THE 00Z GFS RESOLVES THE AXIS AS TWO DISTINCT VORT LOBES...WITH THE MOST AMPLIFIED EASTERN LOBE AFFECTING THE OHIO VALLEY ON SUNDAY. WHILE THE 00Z ECMWF IS MOST MODERATE WITH NEARLY EQUAL STRENGTH ACROSS THE SHEAR AXIS. THE 18Z GEFS MEAN AND 12Z ECMWF ENSEMBLE MEAN WOULD SUPPORT A BLEND OF THE 00Z GFS/ECMWF... AS THE 00Z NAM/CMC/UKMET SEEM TO HAVE AT LEAST ONE SIGNIFICANT FLAW. STILL THOUGH THERE IS SOME AGREEMENT THE DIFFERENCE IN THE 00Z GFS/ECMWF EVOLUTIONS DOES NOT BODE MUCH CONFIDENCE AND REMAINS BELOW AVERAGE. SURFACE LOW TRACKING FROM MO TO THE UPPER MID-ATLANTIC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE SURFACE LOW CURRENTLY OVER CENTRAL MISSOURI WILL CONTINUE TO TRACK NORTHEASTWARD ACROSS THE EASTERN GREAT LAKES ALONG THE NY/PA LINE. ENSEMBLE SURFACE LOWS SHOW AN INCREASINGLY STRONG CLUSTERING WITH THIS TRACK AND THE OPERATIONAL MODELS ALSO FALL WELL WITHIN THIS CLUSTER. THE 00Z CMC IS A BIT FASTER THAN THE 12Z RUN AND REMAINS THE FASTEST SOLUTION...BUT NOT SIGNIFICANTLY SO UNTIL AFTER MOVING OFFSHORE. THE 00Z NAM/UKMET ARE SLOWEST WHILE THE 00Z ECMWF TRACKS A BIT FURTHER NORTH THAN THE REST. THE LARGEST DIFFERENCES OCCUR WITH THE MAGNITUDE OF THE QPF SIGNAL BUT WITH STRONG AGREEMENT IN MASS FIELDS AND QPF ORIENTATION...A BLEND OF THE MOST RECENT OPERATIONAL MODELS WILL BE PREFERRED WITH ABOVE AVERAGE CONFIDENCE. AMPLIFIED NORTHERN STREAM ACROSS CENTRAL/EASTERN CANADA INTO NEW ENGLAND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: AVERAGE FAST MOVING NORTHERN STREAM ACROSS CENTRAL INTO EASTERN CANADA PROGRESSES SMALL AMPLITUDE WAVES INTO NEW ENGLAND BY LATE FRIDAY WITH SOME INCREASED AMPLIFICATION ACROSS NEW ENGLAND THROUGH THE WEEKEND. THE 00Z NAM CONTINUES ITS TREND OF HIGHEST AMPLIFICATION...WHILE A BLEND OF THE 00Z GFS/ECMWF/UKMET/CMC IS IN GOOD AGREEMENT WITH THE ENSEMBLE SOLUTIONS. HOWEVER THIS IS STILL A BIT OF SPREAD REMAINING PARTICULARLY OVER EASTERN CANADA AND NEW ENGLAND ON DAY 3 TO HAVE ONLY AVERAGE CONFIDENCE IN A NON-NAM BLEND AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA