123  
FXUS10 KWNH 060509  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1209 AM EST MON NOV 06 2017  
 
VALID NOV 06/0000 UTC THRU NOV 09/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...COLD FRONT MOVING THROUGH THE NORTHEAST TODAY BUT STALLING OVER  
THE SOUTH TUE/WED...   
..FRONTAL LOW OVER THE TN VALLEY ON TUE
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z GFS / 12Z ECMWF / 12Z UKMET  
CONFIDENCE: ABOVE AVERAGE  
 
GOOD MODEL AGREEMENT EXISTS WITH THE COLD FRONTAL PASSAGE ACROSS  
THE EAST COAST BUT SOME DIFFERENCES CONTINUE REGARDING A FRONTAL  
WAVE IN THE TN VALLEY BY TUE MORNING. THE 00Z NAM IS THE STRONGEST  
OF THE DETERMINISTIC MODELS WHILE THE 12Z UKMET IS RATHER WEAK.  
ENSEMBLE SCATTER LOW PLOTS HAVE BEEN RELATIVELY CONSISTENT WITH A  
PLACEMENT IN E-CNTRL TN FOR 12Z/TUE. A BLEND OF THE 00Z GFS AND  
12Z ECMWF APPEARS BEST FOR THIS SYSTEM THROUGH WEDNESDAY NIGHT.  
 
...POSITIVELY TILTED TROUGH TRANSLATING FROM THE PACIFIC NORTHWEST  
TODAY TO THE PLAINS BY WEDNESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NEAR THE 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE LATEST ENSEMBLE TRENDS SHOW DEEPER WITH THE TROUGH ACROSS THE  
WRN U.S. BY TUE EVENING...BUT THE 00Z GFS TRENDED WEAKER LIKE THE  
12Z CMC. BOTH THE 12Z CMC AND 00Z GFS APPEAR TOO  
DEAMPLIFIED/PROGRESSIVE WITH THE UPPER TROUGH AXIS INTO WED  
MORNING FROM THE CNTRL ROCKIES INTO THE MID-MISSISSIPPI VALLEY.  
THE 00Z NAM IS ON THE STRONGER SIDE OF THE MODEL SPREAD  
HERE...WITH THE 12Z ECMWF AND 12Z UKMET CLOSEST TO THE LATEST  
ENSEMBLE MEANS THROUGH ABOUT WED.  
 
HOWEVER...ON THU...THE 12Z UKMET APPEARS SLOWER THAN MANY OF THE  
ENSEMBLE MEMBERS AND THE 00Z GFS APPEARS CLOSER TO THE BETTER  
ENSEMBLE CLUSTERING ALONG WITH THE 12Z ECMWF. OVERALL...A SOLUTION  
NEAR THE 12Z ECMWF SHOULD WORK FOR ALL FORECAST HOURS THROUGH  
12Z/09 REGARDING THIS SYSTEM...THOUGH THE 12Z UKMET AND 00Z GFS  
ALSO WORK AT TIMES.  
 
...DEEP CYCLONE DROPPING FROM THE GULF OF ALASKA TO OFFSHORE OF  
THE PACIFIC NORTHWEST BY WEDNESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND 12Z ECMWF / 00Z GFS / 12Z UKMET  
CONFIDENCE: AVERAGE  
 
MODELS ARE OVERALL IN FAIRLY GOOD AGREEMENT WITH THIS SYSTEM BUT  
SOME DIFFERENCES IN PLACEMENT OF THE LOW BEGIN TO EMERGE BY  
WEDNESDAY. ENSEMBLE SCATTER LOW PLOTS ARE FAIRLY WIDE RANGING BY  
THU MORNING OFF OF THE PACIFIC NORTHWEST...BUT THE MEANS AGREE  
NEAREST TO THE 00Z GFS AND 12Z ECMWF/UKMET. THE 12Z UKMET/CMC ARE  
NEAR THIS POSITION BUT ARE STRONGER WITH THE SURFACE LOW. GIVEN  
THE ENSEMBLE MEAN STRENGTH OF THE LOW IS DEEPER THAN THE 12Z  
ECMWF...BUT WEAKER THAN THE 12Z UKMET...A GENERAL 3-WAY BLEND OF  
THE 12Z ECMWF...00Z GFS AND 12Z UKMET IS RECOMMENDED TO PROVIDE A  
PLACEMENT/STRENGTH NEAREST TO THE ENSEMBLE MEANS.  
 
...SOUTHERN END OF DEEP UPPER TROUGH LOCATED OVER THE N-CNTRL U.S.  
BY THU MORNING...   
..COLD FRONT SWEEPING THROUGH THE MS VALLEY WED/THU
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECMWF/00Z NAM BLEND  
CONFIDENCE: AVERAGE  
 
BOTH THE 00Z GFS AND 12Z CMC LIE TOWARD THE DEEPER/FASTER SIDE OF  
THE LATEST ENSEMBLE GUIDANCE WITH SHORTWAVE ENERGY DIVING DOWN THE  
WEST SIDE OF AN ANOMALOUS CLOSED LOW OVER WESTERN HUDSON BY ON  
WED. THE MIDDLE OF THE SPREAD IS BETTER REPRESENTED BY A 12Z  
ECMWF/00Z NAM BLEND. WHILE ENSEMBLE TRENDS HAVE BEEN  
FASTER...THERE HAS BEEN GREATER CONVERGENCE OF ENSEMBLE MEMBERS  
NEAR THE 12Z ECMWF/00Z NAM VERSUS THE FASTER 12Z CMC/00Z GFS.  
 
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