906  
FXUS10 KWNH 030623  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
222 AM EDT SAT AUG 03 2019  
 
VALID AUG 03/0000 UTC THRU AUG 06/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND, LESS WEIGHT ON 00Z NAM ON DAY 3  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
---06Z UPDATE---  
NO CHANGE TO THE PRELIMINARY PREFERENCE. THE 00Z ECMWF AND CMC  
TRENDED MORE AMPLIFIED WITH THE EASTERN U.S. TROUGH EARLY NEXT  
WEEK.  
 
---PREVIOUS DISCUSSION---  
MODELS ARE IN FAIRLY GOOD AGREEMENT ACROSS THE CONUS OVER THE NEXT  
FEW DAYS. THE SYNOPTIC PATTERN REMAINS RELATIVELY CONSISTENT, WITH  
A PERSISTENT RIDGE IN THE WESTERN U.S. AND A TROUGH OVER THE EAST  
THAT GETS REINFORCED BY SOME DIGGING WAVES.  
 
THE PRIMARY DIFFERENCES ARE RELATED TO THE TROUGH AMPLITUDE IN THE  
SOUTHEAST AND GULF OF MEXICO BY DAY 3 (MONDAY AND MONDAY NIGHT).  
THE 00Z GFS, NAM AND 18Z GEFS SHOW A MORE AMPLIFIED TROUGH, WHILE  
THE 12Z UKMET, ECMWF AND CMC SHOW A LESS AMPLIFIED TROUGH. DESPITE  
BETTER ENSEMBLE SUPPORT FOR THE ECMWF AND CMC, A STRONG RIDGE OVER  
THE WEST CAN CORRESPOND TO SOME DOWNSTREAM TROUGH AMPLIFICATION SO  
THE GFS AND NAM CANNOT BE RULED OUT. THE GFS AND NAM ARE GENERALLY  
WETTER THAN THE ECMWF -- THIS MAY BE PARTIALLY DUE TO THE  
DIFFERENCES WITH THE TROUGH AND PARTIALLY DUE TO THE USUAL DRY  
BIAS OF THE ECMWF. SLIGHTLY LESS WEIGHT WAS PLACED ON THE ECMWF  
QPF OVER THE SOUTHEAST ON DAY 3.  
 
ONE OTHER DIFFERENCE OF NOTE IS THAT THE 00Z NAM IS PRODUCING A  
VERY FOCUSED MAXIMUM OF QPF OVER THE UPPER MIDWEST ON DAY 3, WITH  
GENERALLY VERY LIGHT QPF ALONG THE REMAINDER OF THE FRONT. THE GFS  
AND ECMWF SHOW A STRONGER QPF SIGNAL ALONG THE LENGTH OF THE  
FRONT, WHICH IS GENERALLY FAVORED. THEREFORE, THE OVERALL  
PREFERENCE IS FOR A GENERAL MODEL BLEND WITH LESS WEIGHT ON THE  
NAM ON DAY 3.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
LAMERS  
 

 
 
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