397   
FXUS10 KWNH 140642  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
241 AM EDT SAT MAR 14 2020  
  
VALID MAR 14/0000 UTC THRU MAR 17/1200 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
00Z FINAL MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..CLOSED LOW DROPPING ALONG THE WEST COAST THROUGH TUESDAY  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
  
07Z UPDATE: GUIDANCE REMAINS WELL CLUSTERED AND NO CHANGES TO THE  
PREFERENCES ARE SUGGESTED.  
  
THE GUIDANCE IS IN VERY GOOD AGREEMENT WITH THE EVOLUTION OF A  
CLOSE LOW MOVING SOUTHWARD FROM JUST OFF THE WASHINGTON STATE  
COAST TO WEST OF THE CENTRAL CALIFORNIA COAST TUESDAY MORNING.  
THERE IS LITTLE DISCREPANCY IN THE POSITION OR INTENSITY OF THIS  
MID-LEVEL FEATURE IN ANY OF THE AVAILABLE GUIDANCE. ALTHOUGH THE  
PRIMARY SYNOPTIC EVOLUTION IS WELL AGREED UPON, THERE DOES EXIST  
DISCREPANCY IN TIMING AND INTENSITY OF SMALLER-SCALE SHORTWAVE  
ROTATING AROUND THE PARENT LOW AND EJECTING ONSHORE THE WEST  
COAST. THESE ARE TOO SMALL TO BE MODELED WELL BEYOND NEAR TERM  
TIME RANGES, AND SINCE THE GENERAL EVOLUTION IS WELL MODELED, A  
GENERAL BLEND IS ACCEPTABLE.  
  
...WEAKENING MID-LEVEL SHORTWAVE MOVING FROM THE SOUTHWEST TO THE  
MID-ATLANTIC INTO SUNDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 00Z NAM/GFS BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
  
07Z UPDATE: THE 00Z NON-NCEP SUITE HAS OVERALL SPED UP ITS  
EJECTION AND SHEARING OF THIS SHORTWAVE AS IT MOVES ACROSS THE  
OHIO VALLEY AND INTO THE MID-ATLANTIC. THIS LEADS TO A MORE  
CLUSTERED GENERAL CONSENSUS, BUT WITH THE GFS REMAINING ON THE  
FAST SIDE OF THE GUIDANCE ENVELOPE, AND THE NAM STILL THE  
STRONGEST SOLUTION, SUGGEST STILL A BLEND WHICH EXCLUDES THE  
NAM/GFS.  
  
THE 00Z GFS IS BY FAR A FAST OUTLIER WITH THE EJECTION OF THIS  
WEAKENING WAVE, BECOMING WELL AHEAD OF THE CONSENSUS AND OTHER  
MODELS AS EARLY AS 12 HOURS INTO THE FORECAST PERIOD. RECENTLY THE  
GFS HAS BEEN VERIFYING TOO FAST, SO EXPECT THIS EVOLUTION IS ALSO  
TOO QUICK AND THE GFS IS REMOVED FROM THE BLEND FOR THIS REASON.  
THE NAM IS DEEPER OVERALL, AS IT IS SLOWER TO SHEAR INTO THE  
WESTERLIES, SO DESPITE ITS SIMILAR PLACEMENT COMPARED TO THE  
PREFERRED CONSENSUS ITS STRENGTH MAKES IT AN OUTLIER. OTHERWISE,  
THE 12Z NON-NCEP BLEND COMBINED WITH THE 18Z GEFS LEAVES A  
SOLUTION THAT IS REASONABLE AND PREFERRED.  
  
...BASE OF LONGWAVE TROUGH OVER THE NORTH-CENTRAL U.S. BY MONDAY  
EVENING...   
..RELATED COLD FRONT ACROSS THE UPPER MIDWEST  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF/UKMET/GEFS AND 12Z ECENS  
CONFIDENCE: AVERAGE  
  
07Z UPDATE: NO SIGNIFICANT CHANGES TO THE PREFERENCES AS THE  
PREVIOUS SIMILARITIES AND DIFFERENCES IN THE GUIDANCE REMAIN WITH  
THE 00Z NON-NCEP SUITE.  
  
THE 00Z GFS IS TOO FAST WITH THE TROUGH AXIS DIGGING THROUGH THE  
NORTHERN PLAINS, WHILE THE NAM IS ON THE OTHER END OF THE GUIDANCE  
MAKING IT A SLOW OUTLIER. THE 12Z CMC IS GENERALLY IN GOOD  
AGREEMENT WITH THE TIMING OF THE TROUGH AS IT PIVOTS EASTWARD, BUT  
IT THE STRONGEST OF THE GUIDANCE AND DRIVES THE COLD FRONT FURTHER  
SOUTH THAN THE PREFERRED CONSENSUS.  
  
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
WEISS  
  
  
 
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