311   
FXUS10 KWNH 190634  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
133 AM EST THU DEC 19 2019  
  
VALID DEC 19/0000 UTC THRU DEC 22/1200 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
00Z MODEL EVALUATION WITH PREFERENCE AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF, 12Z ECMWF ENSEMBLE MEAN, 00Z CMC  
CONFIDENCE: AVERAGE  
  
---06Z UPDATE---  
NO CHANGE TO THE PRELIMINARY PREFERENCE. THE ECMWF REMAINED  
RELATIVELY CONSISTENT WITH THE 12Z ECMWF ENSEMBLE MEAN, AS DID THE  
00Z CMC. THE 00Z UKMET CONVERGED TOWARD THESE MODELS AS WELL.  
  
---PREVIOUS DISCUSSION---  
A SOMEWHAT AMPLIFIED PATTERN ACROSS THE CONUS WILL BECOME  
INCREASINGLY AMPLIFIED OVER THE NEXT FEW DAYS. A STRONG CLOSED LOW  
WILL DEVELOP ALOFT ALONG THE GULF COAST, WITH A LARGE, POSITIVELY  
TILTED TROUGH APPROACHING THE WEST COAST. IN SITUATIONS LIKE THIS,  
THE PREFERENCE IS TO GENERALLY LEAN AWAY FROM THE FASTER WAVE  
PROGRESSION BIAS OF THE GFS AND NAM AS AN AMPLIFYING PATTERN TENDS  
TO SUPPORT SLOWER PROGRESSION OF SYNOPTIC SCALE SYSTEMS.  
  
WITH THE GULF COAST CLOSED LOW, THE TREND OVER THE PAST SEVERAL  
MODEL CYCLES WITH THE GFS HAS BEEN TO SLOW IT DOWN DESPITE THE GFS  
AND GEFS MEMBERS STILL BEING FASTER THAN JUST ABOUT ALL REMAINING  
ENSEMBLE MEMBERS. GIVEN THE SLOWER TREND AND LACK OF SUPPORT FROM  
OTHER MODELS, THE PREFERENCE IS TO LEAN AWAY FROM THE GFS (AND  
NAM, WHICH IS SIMILARLY FAST).  
  
THE 12Z UKMET IS SHOWING THE OPPOSITE -- IT IS GENERALLY ON THE  
SLOWER END OF MODEL GUIDANCE, PARTICULARLY WITH THE GULF COAST  
LOW. AS WITH THE GFS AND NAM, IT CAN'T BE COMPLETELY DISCOUNTED AS  
A POSSIBILITY, BUT THE PREFERENCE IS TO LEAN TOWARD THE ECMWF,  
ECMWF ENSEMBLE MEAN, AND CMC WHICH OFFER AN APPROXIMATE MEDIAN  
SCENARIO AND GOOD CONSISTENCY BETWEEN THEIR FORECAST DEPICTIONS.  
  
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
LAMERS  
  
  
 
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