109  
FXUS10 KWNH 231842  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
141 PM EST THU NOV 23 2017  
 
VALID NOV 23/1200 UTC THRU NOV 27/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH FINAL PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...SLOW-MOVING MID-LEVEL TROUGH OVER THE GULF OF MEXICO LIFTING  
ACROSS THE FL PENINSULA ON FRI...  
...SURFACE LOWS OVER THE EASTERN GULF OF MEXICO/NEAR  
FLORIDA...TRACKING NORTH OVER THE WESTERN ATLANTIC THIS WEEKEND...   
..REINFORCING UPPER TROUGH OVER THE GULF OF MEXICO BY SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z NAM/12Z GFS/12Z ECMWF  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE CURRENT 18Z SURFACE ANALYSIS ALIGNS BEST WITH THE 12Z  
NAM/GFS/ECMWF WHEREAS THE 12Z UKMET/CMC ARE DISPLACED WITH THE  
SURFACE LOW POSITION CURRENTLY LOCATED WEST OF THE FL PENINSULA.  
ENSEMBLE TRENDS WERE REASONABLY WELL CLUSTERED YESTERDAY AND ARE  
SO TODAY BUT THEY THE BEST LOW CLUSTERING HAS SIGNIFICANTLY  
ADJUSTED TOWARD THE MINORITY OF SURFACE LOW PLOTS FROM  
YESTERDAY...CURRENTLY ALIGNED WITH THE 12Z NAM/12Z GFS/12Z ECMWF.  
GIVEN THE AGREEMENT FROM THE 12Z NAM/GFS/ECMWF TO CURRENT  
CONDITIONS AND THE LARGE ADJUSTMENTS SEEN IN THE ENSEMBLES...WILL  
LEAN IN THEIR DIRECTION.  
 
AS THE SURFACE LOW TRACKS UP THE WESTERN ATLANTIC...THE 12Z CMC IS  
FARTHEST WEST OF THE DETERMINISTIC MODELS. AND ON THE WESTERN END  
OF THE LATEST ENSEMBLE SPREAD. THE 12Z NAM IS THE NEXT FARTHEST  
WEST BUT WHEN BLENDED WITH THE 12Z GFS/ECMWF/UKMET...A FAVORED  
COMPROMISE IS REACHED THROUGH SUN. TRENDS IN THE 12Z ECMWF/UKMET  
WERE WEST BUT NOT TO THE DEGREE OF THE 12Z NAM AND CMC.  
 
...UPPER TROUGH AXIS CROSSING THE PACIFIC NORTHWEST AND REACHING  
THE GREAT LAKES BY FRIDAY NIGHT...   
..ASSOCIATED SURFACE LOW CROSSING SOUTHERN CANADA
 
   
..POSSIBLE SHORTWAVE AMPLIFICATION OVER THE NORTHEAST SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-12Z NAM BLEND...WITH THE SURFACE LOW  
12Z GFS/12Z ECMWF BLEND WITH THE HEIGHT FALLS  
CONFIDENCE: AVERAGE  
 
THE 12Z NAM IS SLOWEST WITH THE TRACK OF THE INITIAL UPPER TROUGH  
ACROSS THE N-CNTRL U.S.FRI INTO SAT AND IS CONSIDERED UNLIKELY TO  
VERIFY GIVEN A LACK OF SUPPORT FROM THE OTHER MODEL SOLUTIONS. A  
NON-12Z NAM BLEND IS BELIEVED TO BE BEST FOR THIS PORTION OF THIS  
SYSTEM. THE 12Z ECMWF/UKMET/CMC AGREE WITH A NON 12Z NAM IDEA.  
 
A REINFORCING UPPER TROUGH BUILDS OVER THE NORTHEAST SAT  
NIGHT...WITH A BLEND BETWEEN THE DEEPER 12Z GFS AND LESS AMPLIFIED  
12Z ECMWF APPEARING MOST REASONABLE GIVEN THE LATEST DISTRIBUTION  
OF ENSEMBLE MEMBERS FROM THE GEFS/ECMWF/CMC.  
 
   
..LOW PRESSURE LIFTING UP OFF THE WEST COAST ON SATURDAY
 
   
..DEEP UPPER TROUGH OFFSHORE THE WEST COAST THROUGH SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z ECMWF AND 12Z NAM  
CONFIDENCE: BELOW AVERAGE  
 
LOW CONFIDENCE FORECAST GIVEN ABOVE AVERAGE SPREAD AND CHANGES  
FROM RUN TO RUN BUT THERE SEEMS TO BE A SLIGHT TREND TOWARD BETTER  
AGREEMENT WITH THE 00Z ENSEMBLE SUITE. THESE ENSEMBLES SHOW THE  
12Z GFS AND 12Z UKMET AS NEAR OUTLIERS WITH THE DEPTH OF THE  
SURFACE LOW TO TRACK OFF OF THE NORTHWEST COAST GIVEN ONLY A  
MINORITY OF ENSEMBLES SHOW A CORRESPONDINGLY DEEP 500 MB HEIGHT  
CONTOUR. THE 12Z ECMWF IS SIMILAR TO ITS 00Z CYCLE. WHILE THE 12Z  
ECMWF AND 12Z NAM MAY BE TOO WEAK WITH THE SYSTEM...THEY ARE THE  
CLOSEST DETERMINISTIC GUIDANCE TO WHAT IS BELIEVED TO BE THE  
SOLUTION MOST LIKELY TO VERIFY REGARDING PLACEMENT. THE 12Z CMC  
TRENDED DEEPER RELATIVE TO ITS 00Z CYCLE...IT IS FARTHER  
NORTH/FASTER THAN THE BETTER ENSEMBLE CLUSTERING TO THE SOUTH BY  
12Z/26.  
 
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