404  
FXUS10 KWNH 201932  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
231 PM EST WED NOV 20 2019  
 
VALID NOV 20/1200 UTC THRU NOV 24/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...CLOSED LOW CROSSING THE FOUR CORNERS INTO THE PLAINS  
FRIDAY/SATURDAY...  
...POTENTIAL NORTHERN STREAM SHORTWAVE CROSSING THE NORTH-CENTRAL  
U.S. FRIDAY NIGHT...  
...SURFACE LOW MOVING FROM THE LOWER MISSISSIPPI VALLEY INTO THE  
CENTRAL APPALACHIANS FRIDAY NIGHT INTO SATURDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECMWF/12Z UKMET/00Z ECMWF MEAN BLEND  
CONFIDENCE: BELOW AVERAGE  
   
..17Z UPDATE
 
 
THE 12Z UKMET/CMC JOINED THE ECMWF/GFS CAMP REGARDING THE NORTHERN  
STREAM SHORTWAVE TRACKING THROUGH THE NORTH-CENTRAL U.S. FRIDAY  
NIGHT. THERE REMAIN TIMING DIFFERENCES THOUGH, WITH THE 12Z CMC  
SLOWER THAN THE RELATIVELY SIMILAR 12Z GFS/ECMWF/UKMET. THE 12Z  
ECMWF SHOWS A PERCEIVED IMPROVEMENT TO ITS 00Z CYCLE IN THAT THERE  
IS LESS INTERACTION BETWEEN THE NORTHERN AND SOUTHERN STREAM WAVES  
ACROSS THE EASTERN THIRD OF THE NATION BY LATE SATURDAY WITH THE  
CORRESPONDING SURFACE LOW IN ABOUT THE SAME POSITION BUT WITH A  
WEAKER 850-500 MB STRENGTH AND LESS COLD AIR IN ITS WAKE. BLENDING  
THE 12Z ECMWF WITH THE 00Z ECMWF MEAN AND 12Z UKMET ARE CLOSEST TO  
THE IDEAL MIDDLE GROUND SOLUTION PREFERRED AT THIS TIME.  
   
..PREVIOUS DISCUSSION FOLLOWS
 
 
A COMPLEX INTERACTION OF FEATURES ALONG WITH ABOVE AVERAGE MODEL  
SPREAD AND POOR RUN TO RUN CONSISTENCY RESULTS IN BELOW AVERAGE  
CONFIDENCE REGARDING THE EVOLUTION OF A STORM SYSTEM MOVING FROM  
THE SOUTHWEST TO THE TENNESSEE VALLEY. THE ENSEMBLES ARE IN BETTER  
AGREEMENT WITH THE TRACK OF THE CLOSED LOW OVER SOUTHERN  
CALIFORNIA THIS MORNING. HOWEVER, THE 12Z GFS APPEARS TO BE FASTER  
WITH THE TRACK OF THIS FEATURE STARTING ON FRIDAY.  
 
TO THE NORTH, THERE IS POTENTIAL INTERACTION WITH A SHORTWAVE  
TROUGH WHICH ORIGINATES SOUTH OF ALASKA. AS THIS TROUGH MOVES EAST  
AND ENCOUNTERS A STRONG MID-LEVEL RIDGE OVER BRITISH COLUMBIA. THE  
12Z NAM, 00Z UKMET AND 00Z CMC ARE IN AGREEMENT THAT THE SHORTWAVE  
IS SLIGHTLY SLOWER/STRONGER WITH THE BULK OF THE ENERGY MOVING  
INTO WASHINGTON/IDAHO/MONTANA EARLY FRIDAY. MEANWHILE, THE 12Z GFS  
AND 00Z ECMWF ARE IN AGREEMENT THAT THE SHORTWAVE IS A BIT FASTER  
ALLOWING IT TO TRACK THROUGH/ATOP THE RIDGE AND INTO MINNESOTA BY  
SATURDAY MORNING. ENSEMBLES SHOW THE 12Z GFS AS A STRONG OUTLIER,  
HOWEVER, THE 12Z GFS INITIALIZATION (12Z/20) MATCHES SLIGHTLY  
CLOSER TO OBSERVED WATER VAPOR IMAGERY REGARDING THE SHORTWAVE  
COMPARED TO THE MORE WESTWARD 12Z NAM. FOR THIS REASON, FEEL THE  
12Z GFS/00Z ECMWF IDEA IS MORE LIKELY TO VERIFY BUT TO A WEAKER  
DEGREE THAN DEPICTED BY THE 12Z GFS AND EVEN THE 00Z ECMWF. THE  
00Z ECMWF MEAN TEMPERS THE AMPLITUDE OF THE 00Z ECMWF ENOUGH TO BE  
USED AS A FAVORABLE BLEND FOR THE PREFERENCE.  
 
   
..REMAINDER OF THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-12Z NAM BLEND  
CONFIDENCE: AVERAGE  
   
..17Z UPDATE
 
 
DESPITE SOME MINOR TIMING ADJUSTMENTS, NO SIGNIFICANT CHANGES WERE  
NOTED WITH THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 00Z  
CYCLES.  
   
..PREVIOUS DISCUSSION FOLLOWS
 
 
THE MODELS SHOW GOOD AGREEMENT WITH THE REMAINDER OF THE SYSTEMS  
IMPACTING THE LOWER 48, SPECIFICALLY WITH A DEEPENING MID-LEVEL  
TROUGH/LOW FORECAST TO AFFECT THE UPPER MISSISSIPPI VALLEY AND NEW  
ENGLAND ON THURSDAY AND FRIDAY AND A CLOSED LOW EXPECTED TO FORM  
OFFSHORE OF THE WEST COAST AND DROP SOUTHWARD THIS WEEKEND. THE  
ONLY EXCEPTION ACROSS THE LOWER 48 IS WITH A 500 MB SHORTWAVE TO  
REACH THE CENTRAL PLAINS TONIGHT, WITH A RELATED SURFACE LOW  
TRACKING INTO THE GREAT LAKES REGION ON THURSDAY. THE 12Z NAM WAS  
NOTED TO BE FASTER WITH THE TRACK OF THIS LOW AS WELL AS TO BE  
COLDER IN THE WAKE OF THE LOW/COLD FRONT.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 

 
 
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