906  
FXUS10 KWNH 151610  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1210 PM EDT THU AUG 15 2019  
 
VALID AUG 15/1200 UTC THRU AUG 19/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...INCLUDING PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
EXCEPTION: REMOVE CMC ON D3 ACROSS NORTHERN TIER/S CANADA  
CONFIDENCE: AVERAGE  
 
THE UPPER-LEVEL PATTERN CONTINUES WITH STRONG SOUTHWEST RIDGE AND  
BROAD CYCLONIC FLOW ALONG THE MUCH OF THE NORTHERN PORTION OF THE  
UNITED STATES. THIS TROF PRODUCES BROADLY NORTHWESTERLY FLOW  
ACROSS THE NORTHERN PLAINS INTO THE GREAT LAKES WITH EMBEDDED  
SMALL SCALE SHORTWAVES MOVING THROUGH IT. THE BASE OF THE TROF IS  
CENTERED OVER THE OHIO AND TN VALLEY, WHERE IT INTERSECTS WITH  
RETURN EASTERLY FLOW UNDER THE SUBTROPICAL HIGH NEAR BERMUDA (SW).  
 
THE FRONTAL/CONFLUENCE ZONE AT THIS INTERSECTION CONTINUES TO  
REMAIN FAIRLY ACTIVE BUT ALSO VERY STATIONARY, WITH WEAK WAVES  
ALONG IT. MODELS DO NOT HAVE A STRONG AGREEMENT ON TIMING, BUT  
THERE IS GOOD AGREEMENT ON THE EXISTENCE OF A DOMINANT WAVE  
EMERGING OUT OF THE SOUTHEAST SAT INTO SUNDAY INTO THE NORTHWEST  
ATLANTIC NORTH OF BERMUDA ALONG 40N INTO SUNDAY. THE 12Z NAM/00Z  
UKMET ARE STRONG WHILE THE 12Z GFS/00Z ECMWF SUGGEST MORE  
FLAT/STRUNG OUT FEATURES, BUT OVERALL THE  
PATTERN/ORIENTATION/PLACEMENT SUPPORTS A GENERAL MODEL BLEND FOR  
THIS AREA.  
 
BACK INTO THE NORTHERN STREAM, CONVECTIVELY INDUCED SHORTWAVES  
EMERGE FROM THE NORTHERN ROCKIES THROUGH THE CENTRAL PLAINS INTO  
THE OHIO VALLEY FOR THE NEXT FEW NIGHTS, BEFORE A STRONGER  
NORTHERN STREAM CANADIAN WAVE DROPS EAST OF THE CANADIAN ROCKIES  
INTO THE PRAIRIES, DANGLING A FRONTAL ZONE ACROSS THE NORTHERN  
HIGH PLAINS INTO DAKOTAS DUE TO THE LEAD HEIGHT-FALLS BY EARLY  
SATURDAY. THE 00Z UKMET IS A BIT NORTH/SLOWER WITH THE FRONTAL  
PUSH BUT THE 12Z NAM/GFS HAVE TRENDED TOWARD BETTER AGREEMENT WITH  
THE ECMWF; YET REMAIN SLIGHTLY FASTER TYPICAL OF BIAS. THE 00Z  
CMC ALSO APPEARS A BIT SLOWER THAN CONSENSUS TO SUGGEST LOWER  
WEIGHTING ESPECIALLY BY DAY 3 IN THE NORTHERN TIER/SOUTHERN  
CANADA, BUT OTHERWISE A GENERAL MODEL BLEND APPEARS SOLID. AS  
SUCH A GENERAL MODEL BLEND TRENDING TOWARD A NON-CMC BLEND OR A  
GFS/ECMWF HEAVY WEIGHTED BLEND WILL SUFFICE. WHILE THIS IS  
SHAPING UP A BIT BETTER IN TIMING/PLACEMENT...CONFIDENCE REMAINS  
AVERAGE GIVEN THE IMPORTANCE OF CONVECTION (UPSCALE GROWTH).  
 
THE FAR WESTERN PORTION OF THE LARGE SCALE TROF WILL ALSO START TO  
BECOME A BIT MORE AMPLIFIED AT THE END OF THE WEEKEND, THOUGH THE  
NAM/GFS AND CMC ARE MOST AGGRESSIVE, THE ECMWF, UKMET ARE A BIT  
WEAKER, ALLOWING FOR A SLIGHTLY FASTER SOUTHWARD PROGRESSION.  
LONGER TERM TRENDS SUGGEST THE FORMER HAS A SLIGHTLY PREFERRED  
TREND IN THE ENSEMBLE SUITE BUT NOT SIGNIFICANT ENOUGH TO SUPPORT  
ANYTHING GREATER THAN A GENERAL MODEL BLEND WITH MAYBE A SLIGHT  
INCREASE/WEIGHT TOWARD GFS/GEFS/ECENS AND CMC SOLUTIONS.  
CONFIDENCE IS AVERAGE.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
GALLINA  
 

 
 
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