265  
FXUS10 KWNH 080459  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1158 PM EST TUE NOV 07 2017  
 
VALID NOV 08/0000 UTC THRU NOV 11/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...COLD FRONT PUSHING THROUGH THE SOUTHEAST TODAY WITH SURFACE LOW  
DEVELOPMENT OFF THE EAST COAST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 00Z NAM 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 AND 12Z ECMWF/UKMET/CMC...WHILE THE 00Z NAM IS CLOSER TO THE  
COAST. A NON 00Z NAM BLEND IS PREFERRED GIVEN A LACK OF SUPPORT  
FOR THE 00Z NAM.  
 
   
..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 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.  
 
...DEEP CYCLONE CROSSING INTO THE PACIFIC NORTHWEST THU/FRI WITH  
SHORTWAVES TRACKING EASTWARD THROUGH FRI...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z NAM...12Z ECMWF...12Z UKMET BLEND THROUGH 12Z/10  
00Z GFS...12Z ECMWF...12Z 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...12Z ECMWF AND  
12Z UKMET CLOSER TO THE BETTER ENSEMBLE CLUSTERING.  
 
AFTER 12Z/10...THE 00Z NAM APPEARS 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/12Z ECMWF/12Z UKMET CLOSER TO THE  
BETTER ENSEMBLE CLUSTERING. THE 12Z CMC IS MUCH FLATTER WITH THIS  
TROUGH AXIS. DOWNSTREAM TOWARD THE N-CNTRL U.S. BY FRI EVENING...A  
BLEND OF THE 00Z GFS/12Z ECMWF/12Z UKMET IS CLOSEST TO THE  
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 12Z CMC STANDS OUT THE MOST FROM THE REMAINING  
MODEL CONSENSUS BUT THIS OCCURS NEAR 00Z/11...
AFTER THE DEEPENING  
SURFACE LOW IS WELL INTO EASTERN QUEBEC AND THE COLD FRONT WELL  
OFFSHORE.  
 
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