563   
FXUS10 KWNH 301853  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
252 PM EDT TUE JUL 30 2019  
  
VALID JUL 30/1200 UTC THRU AUG 03/0000 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
12Z MODEL EVALUATION AND FINAL PREFERENCES/CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERVIEW OF THE CONUS FEATURES  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
   
..19Z UPDATE  
  
WITH MOST OF THE MODEL GUIDANCE COMING INTO FAIRLY GOOD AGREEMENT  
WITH THE OVERALL SYNTOPIC PATTERN AND MASS FIELDS, FELT A GENERAL  
MODEL BLEND WOULD SUFFICE ACROSS THE ENTIRE CONUS.  THUS MERGED  
THE REGIONAL DISCUSSIONS INTO ONE MAIN DISCUSSION.  KEEP IN MIND,  
THERE ARE SUBTLE FEATURE DIFFERENCES THAT MAY BE REFLECTED IN THE  
QPF. HOWEVER, THESE DIFFERENCES ARE MINIMAL WITH MORE LOCALIZED  
VARIABILITY THAT IS HARD TO DISCERN FROM A CONUSWIDE MODEL  
EVALUATION AND PREFERENCE EVALUATION.  MANY OF THE KEY FEATURES  
DISCUSSED BELOW, TROUGHING IN THE EAST, RIDGING IN THE SOUTH AND  
WEST AND AN APPROACHING TROUGH IN THE PACIFIC NORTHWEST ARE ALL  
DEPICTED WITH GENERAL AGREEMENT AMONG THE MODEL GUIDANCE AND THEIR  
ENSEMBLES. MORE MESOSCALE FEATURES SHOWN WITH THE MID-LEVEL  
VORTICITY ARE ALL ILLUSTRATED BY THE MODELS, BUT IN TERMS OF  
PLACEMENT AND INTENSITY IT DIFFERS BETWEEN THE MODELS.  THOUGH,  
AGAIN THE DIFFERENCES ARE WITHIN THE ENSEMBLE SPREAD. THEREFORE,  
FELT A GENERAL MODEL BLEND IS PREFERRED WITH NO STRONG SIGNAL OR  
INDICATION TO GO STRONGLY TOWARD A CERTAIN SET OF MODEL GUIDANCE.   
  
   
..PREVIOUS DISCUSSION  
  
MID/UPPER LEVEL TROUGHING EXPECTED ACROSS THE EASTERN CONUS WITH  
RIDGING BUILDING ACROSS THE PLAINS.  MODELS ARE IN FAIRLY GOOD  
AGREEMENT IN TERMS OF MASS FIELDS WITH THE TIMING AND PLACEMENT OF  
THE SURFACE FRONT. THE NORTHERN STREAM COMPONENT OF THE TROUGH IS  
CERTAINLY HELPING TO PUSH THE SURFACE FRONT EASTWARD. MEANWHILE  
THE SOUTHERN STREAM, WHILE WEAK, IS DUE TO A CLOSED UPPER LOW. THE  
MID-LEVEL IMPULSES ROUNDING THE TROUGH IN THE EAST, MOVING ATOP  
THE SURFACE FRONT, WILL LIKELY RESULT IN QPF DIFFERENCES.  THIS IS  
MOST NOTABLE WITH THE 12Z GFS/12Z UKMET/12Z NAM AS VORTICITY IS  
STRONGER AMONG THESE MODELS, ESPECIALLY COMPARED TO THE 12Z ECMWF.  
HOWEVER, THESE DIFFERENCES ARE FAIRLY SMALL AND THE ENSEMBLE  
CLUSTERING SEEMS REASONABLE.  
  
ALSO, MID-LEVEL ENERGY ROUNDING THE AFOREMENTIONED RIDGING ACROSS  
THE PLAINS WILL PROMOTE AN MCS FEATURE THAT IS DEPICTED BY ALL  
MODEL GUIDANCE.  THE 12Z CMC SEEMS TO BE A BIT FARTHER EAST AS  
COMPARED TO THE REST OF THE MODEL GUIDANCE.  HOWEVER, THE  
PLACEMENT AND TIMING DIFFERENCE ARE MINIMAL.  AND IT DOES APPEAR  
THE 12Z ECMWF MAY BE HOLDING ONTO MID-LEVEL ENERGY/DIVERGENCE  
ALOFT A BIT LONGER THAN THE OTHER MODEL GUIDANCE ACROSS PORTIONS  
OF THE PLAINS ON DAY 1 WHICH DOES SEEM TO RESULT IN HIGHER QPF  
ACROSS NE.  HOWEVER, AGAIN, THESE DIFFERENCES WHEN LOOKING AT THE  
MASS FIELDS ARE NOT LARGE ENOUGH TO FAVOR ONE MODEL OVER ANOTHER  
AS MODELS HAVE SHOWN RUN TO RUN CONTINUITY.   
  
MODELS HAVE CONVERGED CLOSER WITH THE EVOLUTION OF THE CLOSED LOW  
APPROACHING THE PACIFIC NORTHWEST, LOCATED JUST OFF OF THE BRITISH  
COLUMBIA COAST, AS IT REACHES THE WEST COAST. THE CLOSED LOW IS  
EXPECTED TO MOVE INLAND INTO CENTRAL BRITISH COLUMBIA WEDNESDAY  
NIGHT WHILE A SHORTWAVE TROUGH AXIS, EXTENDING SOUTHWEST OF THE  
CLOSED LOW, NEARS THE COASTS OF WASHINGTON AND OREGON EARLY FRIDAY  
MORNING. A GENERAL BLEND IS CLOSEST TO THE RELATIVELY AGREEABLE  
ENSEMBLE MEANS AND IS THUS PREFERRED AT THIS TIME.  
  
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
PAGANO  
  
  
 
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