436  
FXUS10 KWNH 160651  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
150 AM EST MON DEC 16 2019  
 
VALID DEC 16/0000 UTC THRU DEC 19/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...MID-LEVEL TROUGH TRACKING FROM THE CENTRAL HIGH PLAINS TO THE  
EASTERN U.S. THROUGH WEDNESDAY MORNING...  
...SURFACE LOW ORGANIZING EAST OF THE MISSISSIPPI RIVER INTO  
TUESDAY MORNING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
   
..07Z UPDATE
 
 
THE 00Z ECMWF/UKMET/CMC TRENDED TOWARD ONE ANOTHER WHILE WHILE THE  
SURFACE LOW OFFSHORE OF NEW ENGLAND CONTINUES TO SHOW SOME  
DIFFERENCES, A BLEND OF THE 00Z NAM/GFS/ECMWF/UKMET/CMC WILL  
PROVIDE A REASONABLE COMPROMISE.  
   
..PREVIOUS DISCUSSION FOLLOWS
 
 
MINOR TIMING DIFFERENCES REMAIN WITH THE 500 MB TROUGH AXIS MOVING  
EASTWARD ALONG WITH LATITUDE DIFFERENCES WITH THE RELATED SURFACE  
WARM FRONT EXTENDING TO THE EAST COAST. THE 12Z ECMWF/UKMET ARE  
SLOWER WHILE THE 00Z NAM/GFS ARE FASTER. THE 12Z CMC IS ALSO  
FASTER BUT DISPLACED SLIGHTLY FARTHER SOUTH WITH THE MAIN AXIS OF  
VORTICITY WITHIN THE MID-LEVEL TROUGH AXIS. AT THIS POINT, A BLEND  
OF THE 00Z NAM, 00Z GFS AND 12Z ECMWF MATCH NEAREST TO THE MIDDLE  
OF THE LATEST MODEL SPREAD, BUT WITH SLIGHTLY LESS WEIGHT ON THE  
12Z ECMWF. AS THE SURFACE LOW TRACKS OFFSHORE, THE 00Z GFS APPEARS  
TOO FAR NORTH BUT THE 12Z ECMWF TOO FAR SOUTH. MODERATE SPREAD  
REMAINS IN THE ENSEMBLE SCATTER LOW PLOTS WHICH IS PREVENTING  
HIGHER CONFIDENCE WITH THIS SYSTEM.  
 
...MID-LEVEL SHORTWAVE CLIPPING THE GREAT LAKES TUESDAY NIGHT AND  
REACHING NEW ENGLAND LATE WEDNESDAY...--  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
   
..07Z UPDATE
 
 
THE 00Z UKMET ADJUSTED TO THE REMAINING MODEL CONSENSUS AND LITTLE  
IN THE WAY OF DIFFERENCES REMAIN. THEREFORE, A GENERAL MODEL BLEND  
IS PREFERRED.  
   
..PREVIOUS DISCUSSION FOLLOWS
 
 
A DEEP BUT COMPACT CLOSED LOW SWINGS THROUGH THE NORTHERN GREAT  
LAKES REGION TUESDAY. MODEL AGREEMENT IS FAIRLY GOOD, BUT THE 12Z  
UKMET STANDS OUT AS A SLOW DETERMINISTIC OUTLIER. BETTER SUPPORT  
EXISTS FOR A NON 12Z UKMET BLEND AT THIS TIME.  
 
   
..TROUGH APPROACHING THE WESTERN U.S. TUESDAY NIGHT
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF/12Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
   
..07Z UPDATE
 
 
THE 00Z UKMET AND 00Z ECMWF SPED UP WHILE THE 00Z CMC SLOWED DOWN  
WITH THE 500 MB TROUGH THAT REACHES THE WEST COAST. THE 00Z  
ECMWF/UKMET CONSENSUS IS JUST A BIT FASTER THAN PREFERRED GIVEN  
THE LATEST ENSEMBLE SPREAD. A BLEND OF THE 12Z/15 ECMWF AND 00Z/16  
ECMWF APPEARS BEST FOR THE WESTERN U.S. AT THIS TIME.  
   
..PREVIOUS DISCUSSION FOLLOWS
 
 
THE LATEST MODELS AGREE WITH A CLOSED LOW WITHIN THE BASE OF A  
TROUGH AXIS NEARING THE WEST COAST TUESDAY NIGHT. TIMING  
DIFFERENCES SHOW UP ON TUESDAY WITH THE 00Z NAM SLOWER AND 12Z  
UKMET, 00Z GFS AND 12Z CMC FASTER. THROUGH THURSDAY MORNING, THE  
12Z CMC IS FASTEST WITH THE 00Z GFS NEXT FASTEST. THE 00Z NAM  
SPEEDS UP TOWARD THE MIDDLE WHILE THE 12Z UKMET SLOWS DOWN TOWARD  
THE MIDDLE BY WEDNESDAY EVENING. ALL IN ALL, A MIDDLE OF THE ROAD  
TO SLIGHTLY SLOWER APPROACH IS FAVORED GIVEN LARGE ENSEMBLE SPREAD  
AND A TREND TO BE SLOWER. THIS PLACEMENT IS CLOSE TO A 12Z  
ECMWF/UKMET BLEND FROM MONDAY THROUGH THURSDAY MORNING ACROSS THE  
WEST.  
 
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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