906  
FXUS10 KWNH 221709  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1208 PM EST WED NOV 22 2017  
 
VALID NOV 22/1200 UTC THRU NOV 26/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT  
RANGE FORECASTS.  
 
...UPPER TROUGH DEPARTING FROM THE NORTHEAST TODAY WITH RELATED  
SURFACE LOWS...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
REMAINING MODEL DIFFERENCES ARE MINOR...WITH A GENERAL MODEL  
COMPROMISE SUFFICING FOR THIS SYSTEM. THE 12Z GFS...00Z ECMWF AND  
00Z UKMET ARE CLOSEST TO THE LATEST ENSEMBLE CONSENSUS BUT THE 12Z  
NAM AND 00Z CMC ARE NOT FAR OFF.  
 
...SLOW MOVING MID-UPPER LEVEL TROUGH ALONG THE GULF COAST THROUGH  
FRIDAY...   
..SURFACE LOWS IN THE EASTERN GULF OF MEXICO/NEAR FLORIDA
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS / 00Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE 12Z NAM APPEARS TO BE IN THE MINORITY OF ENSEMBLE MEMBERS  
REGARDING 500 MB...AND AT THE SURFACE. THE 00Z UKMET IS REASONABLY  
SIMILAR TO THE 12Z GFS AND ARE FASTER THAN THE 00Z ECMWF. ENSEMBLE  
TRENDS SUPPORT SOME MIDDLE GROUND BETWEEN THE FASTER 12Z GFS AND  
SLOWER 00Z ECMWF.  
 
...UPPER TROUGH AXIS CROSSING THE PACIFIC NORTHWEST TODAY AND  
REACHING THE GREAT LAKES FRI NIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM/00Z ECMWF/00Z UKMET THROUGH 00Z/25  
00Z UKMET 00Z/25-00Z/26  
CONFIDENCE: AVERAGE  
 
THE 12Z GFS TIMING APPEARS TOO FAST WITH THIS SYSTEM WHILE THE 12Z  
NAM/00Z ECMWF/00Z UKMET APPEAR SIMILAR TO ONE ANOTHER AND THE  
ENSEMBLE CONSENSUS THROUGH ABOUT 00Z/25. AFTER THIS TIME...THE 00Z  
ECMWF APPEARS TOO DEEP WITH THE UPPER TROUGH AND SOUTHWARD  
DISPLACED WHILE THE 12Z NAM ENDS UP MORE PROGRESSIVE THAN MOST.  
THIS LEAVES THE 00Z UKMET AS A PREFERRED MIDDLE GROUND.  
 
   
..SYSTEM APPROACHING THE WEST COAST SATURDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF/UKMET/CMC BLEND  
CONFIDENCE: BELOW AVERAGE  
 
AN AMPLIFIED PACIFIC PATTERN AT THE START SUPPORTS SLOWER  
PROGRESSION TO UPPER TROUGH MOVEMENT TOWARD THE EAST. SEVERAL  
DETERMINISTIC MODELS HAVE TRENDED SLOWER BUT ENSEMBLE TRENDS ARE  
QUICKER WHICH LOWERS CONFIDENCE HERE. ENSEMBLE SCATTER LOW PLOTS  
AND ENSEMBLE MEANS SUPPORT A SURFACE LOW BETWEEN THE 00Z ECMWF AND  
00Z UKMET POSITION APPEARS REASONABLE WHICH IS ALSO NEAR THE 00Z  
CMC. THE 12Z NAM APPEARS REASONABLE WITH THE 500 MB REFLECTION BUT  
IS LESS DEVELOPED WITH A SURFACE LOW OFF OF THE WEST COAST THROUGH  
00Z/26.  
 
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