692  
FXUS10 KWNH 161659  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1259 PM EDT FRI AUG 16 2019  
 
VALID AUG 16/1200 UTC THRU AUG 20/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z PRELIMINARY MODEL EVALUATION...INCLUDING PREFERENCES AND  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS, 00Z ECMWF, AND ECENS/GEFS MEAN  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
FLOW ACROSS THE CONUS WILL REMAIN BROADLY CYCLONIC THROUGH THE  
FORECAST PERIOD, ALTHOUGH SUBTLE HEIGHT RISES ARE LIKELY SUNDAY  
INTO EARLY NEXT WEEK. THIS BROAD CYCLONIC FLOW PERSISTS IN  
RESPONSE TO REPEATED REPLACEMENT OF A LONGWAVE TROUGH AXIS, FIRST  
ACROSS THE EASTERN CONUS THROUGH SATURDAY, THEN SHIFTING TO THE  
WEST BY SUNDAY INTO EARLY NEXT WEEK. SHORTWAVES ROTATING THROUGH  
THE FLOW WILL BE THE PRIMARY SENSIBLE WEATHER MAKERS, AND IT IS  
DISCREPANCY AMONG THESE FEATURES THAT LEAD TO THE PREFERRED BLEND.  
 
THE MOST NOTABLE DIFFERENCES INVOLVES THE 12Z NAM WHICH CONTINUES  
TO BE A STRONG OUTLIER WITH SEVERAL OF THESE VORT LOBES SHEDDING  
AROUND A COMPLEX OF UPPER LOWS IN CANADA. THROUGH DAY 2 /SUNDAY/  
THE DIFFERENCE IS RATHER MINIMAL, BUT BY DAY 3 THE ENERGY IS MUCH  
TOO STRONG, AS WELL AS A SOUTHERN OUTLIER, WHEN COMPARED TO THE  
GLOBAL CONSENSUS AND THE ENSEMBLE ENVELOPE. THE 00Z UKMET  
CONTINUES ITS TREND OF BEING TOO WARM WITH ITS HEIGHTS/THICKNESSES  
ACROSS THE CONUS, BUT MOST NOTABLY DEVELOPS AN IMPRESSIVE LOW AT  
THE TAIL END OF A COLD FRONT IN THE GULF AND LIFTS IT INTO THE  
EASTERN CAROLINAS EARLY NEXT WEEK. WHILE THE ECMWF AND GFS BOTH  
SHOW HINTS OF ENERGY IN THIS SAME POSITION, THEY ARE MUCH WEAKER  
AND MORE REALISTIC COMPARED TO REALITY BASED ON CURRENT PROGS. THE  
CMC IS GENERALLY TOO FAST WITH MANY OF THESE IMPULSES, OUTPACING  
THE REST OF THE GLOBAL GUIDANCE.  
 
WHILE QPF WILL LIKELY BE SIGNIFICANT NEAR FL AND THE SOUTHEAST, AS  
WELL AS WITHIN ANY EMBEDDED SHORTWAVES TRAVERSING THE MIDDLE OF  
THE CONUS, THERE STILL REMAINS ENOUGH UNCERTAINTY IN PLACEMENT AND  
AMOUNTS TO HEDGE AWAY FROM THE EXTREME NUMBERS FORECAST BY THE  
UKMET AND NAM. FOR CONSISTENCY AND TO REMOVE SOME OF THE SMALL  
DETAILS, A BLEND OF THE ECMWF/GFS AND THEIR ASSOCIATED MEANS  
REMAINS PREFERRED.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
WEISS  
 

 
 
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