969  
FXUS10 KWNH 231658  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1157 AM 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 NAM/GFS EVALUATION...WITH PRELIMINARY 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/00Z ECMWF  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE CURRENT 15Z SURFACE ANALYSIS ALIGN BEST WITH THE 12Z NAM/GFS  
AND 00Z ECMWF WHEREAS THE 00Z 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/00Z ECMWF.  
GIVEN THE AGREEMENT FROM THE 12Z NAM/GFS TO CURRENT CONDITIONS AND  
THE LARGE ADJUSTMENTS SEEN IN THE ENSEMBLES...WILL GO WITH THE  
MORE RECENTLY INITIALIZED MODELS AND THE 00Z ECMWF WHICH AGREES  
WITH THE 12Z NAM/12Z GFS.  
 
AS THE SURFACE LOW TRACKS UP THE WESTERN ATLANTIC...THE 12Z NAM IS  
CLOSER TO THE EAST COAST THAN THE 12Z GFS AND 00Z ECMWF.  
HOWEVER...A 3-WAY BLEND OF THESE THREE MODELS IS CONSIDERED BEST  
AND IS SUPPORTED AMONG THE SPREAD IN ENSEMBLE SCATTER LOW PLOTS  
THROUGH SUNDAY MORNING.  
 
...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/00Z 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.  
 
A REINFORCING UPPER TROUGH BUILDS OVER THE NORTHEAST SAT  
NIGHT...WITH A BLEND BETWEEN THE DEEPER 12Z GFS AND LESS AMPLIFIED  
00Z 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 00Z 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 00Z 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. WHILE THE 00Z 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. THE 00Z CMC IS  
LESS AGGRESSIVE WITH SHORTWAVE ENERGY AND WEAKEST WITH THE  
CORRESPONDING SURFACE LOW OFF OF THE NORTHWEST COAST...AND FALLS  
INTO A STRONG MINORITY OF SOLUTIONS.  
 
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