116  
FXUS10 KWNH 100818  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
417 AM EDT FRI JUL 10 2020  
 
VALID JUL 10/0000 UTC THRU JUL 13/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH FINAL PREFERENCES/CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...MID-LEVEL SHORTWAVE CROSSING THE GREAT LAKES/OHIO VALLEY  
THROUGH SAT...   
..ASSOCIATED COLD FRONT CROSSING THE GREAT LAKES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 00Z GFS BLEND  
CONFIDENCE: BELOW AVERAGE  
 
07Z UPDATE...THERE IS BETTER AGREEMENT WITH THE MID-LEVEL  
SHORTWAVE FROM THE 00Z ECMWF/UKMET/CMC, WHICH SHOW THE 00Z GFS OUT  
ON ITS OWN WITH A FASTER TRACK AS THE VORT CENTER TRACKS INTO THE  
NORTHEAST.  
 
RUN TO RUN CONSISTENCY HAS BEEN POOR WITH THIS SYSTEM AND THE  
CHANGES SEEN IN THE 12Z/10 ENSEMBLE SPAGHETTI PLOTS COMPARED TO  
THE PREVIOUS 00Z/10 CYCLE ARE DRAMATIC VALID SATURDAY MORNING. THE  
LATEST CONSENSUS IS NEAR THE AGREEABLE GEFS/EC ENSEMBLE MEANS  
WHICH SHOW THE MID-LEVEL TROUGH PROGRESSING SLOWER THAN THE 00Z  
GFS. A BLEND OF THE 00Z NAM (WEAKER/NORTH) AND 12Z ECMWF  
(STRONGER/SOUTH) MAY BE THE BEST COMPROMISE AS NO SINGLE MODEL  
SOLUTION LOOKS IDEAL HERE. THE 12Z CMC IS WEAKER AND FASTER THAN  
THE ENSEMBLE MEANS WITH THE MID-LEVEL TROUGH WHILE THE 12Z UKMET  
IS RATHER STRONG AND NORTH WITH THE MID-LEVEL LOW CENTER.  
 
   
..TROPICAL STORM FAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND THROUGH 12Z/11 CLOSEST TO 03Z NHC  
ADVISORY  
00Z ECMWF/UKMET BLEND 12Z/11-12Z/12 CLOSEST TO 03Z NHC  
ADVISORY  
CONFIDENCE: REFER TO NHC  
 
07Z UPDATE...THE 00Z ECMWF/UKMET ADJUSTED FASTER, CLOSER TO THE  
03Z NHC ADVISORY, LEAVING THE 00Z DETERMINISTIC CONSENSUS FAIRLY  
CLOSE TO THE 03Z NHC ADVISORY FOR THE TRACK OF FAY. BEYOND  
SATURDAY MORNING, THE MODELS DIVERGE LEAVING THE 00Z ECMWF/UKMET  
CLOSEST TO NHC.  
 
THE DETERMINISTIC MODELS VARY WITH CLOSENESS TO THE 03Z NHC  
ADVISORY FOR FAY OVER THE NEXT 48 HOURS. HOWEVER, OVERALL, A BLEND  
OF THE 00Z NAM/12Z ECMWF AND 12Z CMC IS NEAREST TO THE TRACK FOR  
FAY AS THE STORM MOVES INTO THE NORTHEAST FRIDAY NIGHT. THE  
NAM/ECMWF COMBINATION FALLS A BIT WEST OF THE NHC TRACK, AND A  
POSSIBLE OVER AMPLIFICATION OF AN UPSTREAM (OH VALLEY) TROUGH SEEN  
IN THE 12Z ECMWF MAY BE TO BLAME AS DISCUSSED IN THE ABOVE SECTION.  
 
...MID-LEVEL SHORTWAVE TO CROSS THE NORTHERN ROCKY MOUNTAINS EARLY  
FRIDAY MORNING, MOVE ATOP THE RIDGE AND INTO THE UPPER MIDWEST BY  
SAT EVENING, REACHING THE OH VALLEY ON SUN...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
07Z UPDATE...ADJUSTMENTS IN THE 00Z ECMWF TOWARD THE REMAINING  
CONSENSUS SUPPORT BETTER AGREEMENT WITH THIS FEATURE AS IT CROSSES  
THE MISSISSIPPI RIVER VALLEY. DESPITE SOME MINOR TIMING  
DIFFERENCES, THE AGREEMENT IS GOOD ENOUGH AT THIS POINT TO SUPPORT  
A GENERAL MODEL BLEND.  
 
THE 00Z NAM/GFS ARE CLOSE TO ONE ANOTHER WITH THIS SYSTEM AS IT  
NEARS THE MISSISSIPPI RIVER, BUT TEND TO BE A LITTLE SLOWER THAN  
THE ENSEMBLE MEANS. MEANWHILE THE 12Z UKMET/CMC ARE SOUTH OF THE  
ENSEMBLE MEANS. A BLEND OF THESE MODELS MAY BE BEST FOR THIS  
SYSTEM WITH ONLY THE WEAKLY DEFINED 12Z ECMWF STANDING OUT  
SIGNIFICANTLY FROM THE REMAINING CONSENSUS.  
 
...LONGWAVE TROUGH AXIS MOVING INTO WESTERN CANADA AND THE  
NORTHWESTERN U.S. ON SUN...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
07Z UPDATE...ONLY MINOR TIMING ADJUSTMENTS WERE NOTED IN THE 00Z  
ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 12Z CYCLES. GIVEN THE  
MINOR DIFFERENCES NOTED WITH THE LARGE TROUGH AXIS REACHING THE  
NORTHWESTERN U.S. THIS WEEKEND, A GENERAL MODEL BLEND WILL WORK  
WELL HERE FOR THE PREFERENCE.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:  
HTTPS://WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERM  
INATION.PDF  
 
OTTO  
 

 
 
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