302  
FXUS10 KWNH 051654  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1153 AM EST TUE DEC 05 2017  
 
VALID DEC 05/1200 UTC THRU DEC 09/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..CLOSED LOW DEPARTING FROM ONTARIO THROUGH WEDNESDAY
 
   
..COLD FRONT MOVING ACROSS THE EAST COAST TODAY/TONIGHT
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
ONLY MINOR DIFFERENCES WERE NOTED IN THE LATEST GUIDANCE WITH A  
GENERAL MODEL COMPROMISE RECOMMENDED TO SMOOTH OUT SMALLER SCALE  
DIFFERENCES.  
 
...SHORTWAVE TROUGH AXIS CURRENTLY OVER THE SOUTHWEST AND DROPPING  
SOUTHWARD ...  
...REINFORCING SHORTWAVE TROUGH AXIS ARRIVING INTO THE SOUTHWEST  
THU MORNING AND MOVING ACROSS TX FRI MORNING ...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NEAR THE 00Z ECMWF MEAN  
CONFIDENCE: AVERAGE  
 
THE FIRST SHORTWAVE WEAKENING SOUTHEASTWARD FROM CA/AZ SHOWS GOOD  
AGREEMENT IN THE MODEL GUIDANCE BUT THERE ARE DIFFERENCES TO TALK  
ABOUT REGARDING A SHORTWAVE AMPLIFYING SOUTHWARD ACROSS THE CNTRL  
ROCKIES WED/WED NIGHT. MODEL AND DETERMINISTIC TRENDS HAVE BEEN  
TOWARD THE WEST/MORE AMPLIFIED WITH THE SHORTWAVE VALID THU  
EVENING.  
 
THE 12Z GFS IS THE WEAKEST AND MOST PROGRESSIVE WITH THE  
POSITIVELY TILTED TROUGH AXIS STRETCHING FROM THE MS VALLEY INTO  
NRN MEXICO FRI MORNING. GIVEN THE ENSEMBLE TRENDS TOWARD A  
SLOWER/DEEPER TROUGH AXIS...AWAY FROM THE 12Z GFS AND 00/06Z  
GEFS...DO NOT WANT TO BE ON THE FASTER EDGE OF THE MODELS. THE 00Z  
ECMWF/UKMET REPRESENT THE MORE AMPLIFIED SIDE OF THE MODEL SPREAD.  
THE 00Z ECWMF MEAN IS A BIT WEAKER THAN THE 00Z ECMWF AND  
CERTAINLY THE 00Z UKMET WITH THE UKMET DEEPEST. THE 00Z ECMWF MEAN  
APPEARS TO BE THE BEST MIDDLE GROUND WITH THIS SYSTEM WHICH IS  
BETWEEN THE FLATTER/MORE PROGRESSIVE 12Z NAM/GFS AND MORE  
AMPLIFIED 00Z UKMET/ECMWF. THE 00Z CMC IS ALSO IN THE MIDDLE HERE  
BUT SHOWS LESS SEPARATION BETWEEN THIS FEATURE AND THE NRN STREAM  
TROUGH OVER THE GREAT LAKES REGION...WHICH IS NOT PREFERRED.  
 
...CLOSED LOW LIKELY FORMING OVER SRN ONTARIO ON FRI WITH ADJACENT  
SHORTWAVE AMPLIFYING SOUTHWARD TO ITS WEST THROUGH FRI EVENING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF/UKMET BLEND  
CONFIDENCE: AVERAGE  
 
BY FRI...THE 12Z NAM/GFS ARE LOCATED THE FARTHEST NORTH OF THE  
DETERMINISTIC GUIDANCE REGARDING THE CLOSED LOW AND ARE MORE  
AMPLIFIED WITH THE SHORTWAVE LOCATED OVER THE UPPER MS VALLEY  
00Z/09. THE LATEST ENSEMBLE SPREAD IS FAIRLY LARGE BUT SOME  
CONVERGENCE HAS BEEN NOTED OVER THE PAST 4 CYCLES. THE GFS HAS  
DONE SOME FLIP FLOPPING WITH ITS 12/00Z CYCLES BUT THE UKMET HAS  
BEEN FAIRLY CONSISTENT OVER ITS PAST 3 RUNS AND LIES NEAR THE  
GREATEST ENSEMBLE CLUSTERING. THE 00Z ECMWF IS CURRENTLY A BIT  
DEEPER THAN THE 00Z UKMET VALID 00Z/09...BUT A BLEND OF THESE TWO  
MODELS SEEMS BEST AT THIS TIME.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page