770  
FXUS10 KWNH 080656  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
155 AM EST WED NOV 08 2017  
 
VALID NOV 08/0000 UTC THRU NOV 11/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH FINAL PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...COLD FRONT PUSHING THROUGH THE SOUTHEAST TODAY WITH SURFACE LOW  
DEVELOPMENT OFF THE EAST COAST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GFS...00Z UKMET..00Z CMC BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
NO MODEL DIFFERENCES WERE NOTED WITH THE COLD FRONTAL TIMING...BUT  
THERE WERE DIFFERENCES REGARDING TWO SURFACE LOWS FORECAST TO FORM  
EAST OF THE MID-ATLANTIC REGION. ONE LOW EARLY THIS MORNING SHOWS  
FAIR MODEL AGREEMENT BUT WITH THE SECOND LOW EXPECTED TO FORM THU  
NIGHT...THE ENSEMBLE SCATTER LOW PLOTS BETTER ALIGN WITH THE 00Z  
GFS...00Z UKMET AND 00Z CMC...WHILE THE 00Z NAM AND 00Z ECMWF ARE  
CLOSER TO THE COAST. VERY LITTLE ENSEMBLE SUPPORT FOR THE WESTERN  
SOLUTIONS LIKE THE 00Z NAM AND 00Z ECMWF.  
 
   
..POSITIVELY TILTED TROUGH OVER THE PLAINS THIS MORNING
 
 
...PAIR OF SHORTWAVES TRACKING ESEWD AND REACHING OK AND WEST TX  
TODAY WITH THE NORTHERN SHORTWAVE EXPECTED TO REACH THE SOUTHEAST  
BY THURSDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z NAM/GFS/ECWMF BLEND  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE MODELS CONTINUE TO SHOW RATHER SIGNIFICANT DIFFERENCES FOR  
THIS SHORT TERM FORECAST PROBLEM...WITH THE ISSUE ARISING FROM  
POTENTIAL INTERACTION BETWEEN TWO VORTICITY MAXIMA...ONE CURRENTLY  
OVER COLORADO AND THE OTHER OVER THE CA/AZ BORDER. ENSEMBLE TRENDS  
HAVE BEEN CONFLICTING...BUT THE 12Z ECMWF SHOWS TOWARD THE SLOW  
SIDE OF THE LATEST ENSEMBLE/DETERMINISTIC GUIDANCE GIVEN MORE  
INTERACTION WITH THESE TWO VORTICITY MAXIMA NEAR THE LOWER MS  
VALLEY THU MORNING. THE 12Z CMC REMAINS A FASTER/PROGRESSIVE  
OUTLIER WITH BETTER ENSEMBLE CLUSTERING AND THE 00Z DATA  
ASSIMILATION FAVORING THE 00Z NAM/GFS COMBO WITH THIS SYSTEM AS IT  
CROSSES THE SOUTHEAST. THE 12Z UKMET IS A BLEND OF THE 00Z NAM/GFS  
IDEA AND THE SLOWER 12Z ECMWF IDEA. RUN TO RUN CONTINUITY HAS BEEN  
RATHER POOR IN THE DETAILS WHICH MAKES FOR A SLIGHTLY BELOW  
AVERAGE FORECAST CONFIDENCE.  
 
07Z UPDATE: THE 00Z ECMWF AND 00Z UKMET ADJUSTED FROM THEIR 12Z  
CYCLES WITH THE ECMWF TRENDING FASTER TOWARD THE 00Z NAM/GFS WHILE  
THE UKMET TRENDED SLOWER. ENSEMBLE SPAGHETTI HEIGHT PLOTS SHOW THE  
00Z UKMET AS A NEAR OUTLIER WITH THE 00Z ECMWF A BIT DEEPER/SLOWER  
THAN THE 00Z NAM/GFS BUT WITHIN REASON AND FASTER THAN THE 00Z  
UKMET. STILL...WHILE THE 00Z ECMWF IS ON THE EDGES OF THE ENSEMBLE  
GUIDANCE WHEN BLENDED WITH THE FASTER 00Z NAM/GFS A PREFERRED  
COMPROMISE IS REACHED.  
 
...DEEP CYCLONE CROSSING INTO THE PACIFIC NORTHWEST THU/FRI WITH  
SHORTWAVES TRACKING EASTWARD THROUGH FRI...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z NAM...00Z ECMWF...00Z UKMET BLEND THROUGH 12Z/10  
00Z GFS...00Z ECMWF...00Z UKMET BLEND 12Z/10-12Z/11  
CONFIDENCE: AVERAGE  
 
WHILE THERE ARE MANY DETAIL DIFFERENCES WITH INDIVIDUAL VORTICITY  
MAXIMA REVOLVING AROUND THE LARGE MID-LEVEL LOW CENTER OFFSHORE OF  
THE PACIFIC NORTHWEST REDUCING CONFIDENCE IN THE DETAILS...THERE  
ARE SOME LARGER SCALE DIFFERENCES WHERE PICKING AND CHOOSING  
MODELS MAY BE MORE SKILLFUL. THE 00Z GFS IS THE ONLY DETERMINISTIC  
MODEL THAT MERGES TWO OF THE LARGER VORTICITY MAXIMA INTO A MORE  
DEFINED 500 MB LOW CENTER BY 12Z/10 OFF OF THE COAST OF OREGON.  
THE ENSEMBLES SHOW THIS SOLUTION TO BE ON THE FAR WESTERN EDGE OF  
THE LATEST MEMBERS...WITH A BLEND OF THE 00Z NAM...00Z ECMWF AND  
00Z UKMET CLOSER TO THE BETTER ENSEMBLE CLUSTERING.  
 
AFTER 12Z/10...THE 00Z NAM AND 00Z CMC APPEAR TO SHOW TOWARD THE  
SLOW SIDE OF THE MODEL GUIDANCE CONCERNING THE 500 MB TROUGH AXIS  
OVER OREGON WITH A BLEND OF THE 00Z GFS/ECMWF/UKMET CLOSER TO THE  
BETTER ENSEMBLE CLUSTERING AND ENSEMBLE MEANS.  
 
...AMPLIFYING NORTHERN STREAM TROUGH/CLOSED LOW NEAR GREAT LAKES  
INTO FRIDAY MORNING...   
..COLD FRONT CROSSING THE NORTHERN TIER STATES WED-FRI
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL CONSENSUS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THERE ARE ONLY MINOR DIFFERENCES WITH THIS SYSTEM...IF  
ANYTHING...THE 00Z CMC STANDS OUT THE MOST FROM THE REMAINING  
MODEL CONSENSUS BUT THIS OCCURS STARTING 00Z/11. THE 00Z CMC  
SURFACE LOW IS FARTHEST SOUTH COMPARED TO THE OTHER MODELS BUT  
THIS IS AFTER THE DEEPENING SURFACE LOW AND COLD FRONT HAVE MOVED  
FAR ENOUGH AWAY FROM THE LOWER 48 TO NOT BE MUCH OF A FACTOR IN  
THE FORECAST.  
 
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