088  
FXUS10 KWNH 110452  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1151 PM EST FRI NOV 10 2017  
 
VALID NOV 11/0000 UTC THRU NOV 14/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH LATEST MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
   
..LEAD SHORTWAVE OVER NORTH DAKOTA
 
EJECTING EAST ALONG THE  
US-CANADA BORDER THROUGH THE WEEKEND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
AS WAS THE PREFERENCE WITH THE 12Z MODEL CYCLE...A NON-CMC BLEND  
IS PREFERRED AND IS CONTINUED NOW. THE 12Z CMC SHEARS OUT THE VORT  
MAX AND DEAMPLIFIES THE SHORTWAVE MUCH FASTER THAN THE OTHER  
MODELS...WHILE THERE IS VERY GOOD AGREEMENT ON TIMING AND STRENGTH  
OF THE SHORTWAVE AMONG THE OTHER MODELS.  
 
   
..SECONDARY TROUGH OVER THE PACIFIC NORTHWEST PROGRESSING EAST
 
 
...GRADUALLY AMPLIFYING WAVE OVER THE EASTERN CONUS FROM SUNDAY  
INTO MONDAY WITH SURFACE WAVE OR LOW DEVELOPMENT OFF THE EAST  
COAST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 00Z GFS / 12Z UKMET / 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
DIFFERENCES WITH THIS SYSTEM BECOME MORE APPARENT AFTER THE WAVE  
REACHES THE PLAINS AND BEGINS A GRADUAL AMPLIFICATION EASTWARD TO  
THE EAST COAST. ENSEMBLE SENSITIVITY ANALYSIS FROM NAEFS AND ECMWF  
MEMBERS INDICATE THAT THE STRENGTH AND POSITION OF ANY POSSIBLE  
SURFACE WAVE OR LOW DEVELOPING OFF THE EAST COAST (LATE MONDAY AND  
INTO TUESDAY) IS SENSITIVE TO THE STRENGTH OF THE WAVE ALOFT  
INITIALLY AS IT MOVES THROUGH THE ROCKIES. THE ENSEMBLE CLUSTERS  
ALSO SHOW VERY LITTLE SUPPORT FOR THE DEVELOPMENT OF A STRONGER  
SURFACE WAVE OR CLOSED LOW OFF THE COAST.  
 
THE 00Z NAM AND 12Z CMC ARE THE MODELS THAT INDICATE MORE  
SUBSTANTIAL SURFACE CYCLOGENESIS OFF THE EAST COAST EARLY NEXT  
WEEK. THEY HAVE A MORE AMPLIFIED TROUGH AS COMPARED TO THE OTHER  
MODELS. GIVEN THE FAR GREATER SUPPORT FROM ENSEMBLES...AND THE  
LACK OF EVIDENCE THAT THE TROUGH OVER THE NORTHWEST IS NOTABLY  
STRONGER THAN FORECAST...THE PREFERENCE WITH THIS SYSTEM IS FOR A  
BLEND OF THE GFS...UKMET...AND ECMWF.  
 
...UPPER TROUGH DROPPING SOUTH OFFSHORE THE PACIFIC NORTHWEST THIS  
WEEKEND WITH A SHORTWAVE KICKING INLAND ON MONDAY...  
...STRONG CYCLONE REFOCUSING OFF THE COAST OF BRITISH COLUMBIA  
LATE MONDAY AND INTO TUESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC CONSENSUS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS HANDLE THE DETAILS WITH THIS SYSTEM  
DIFFERENTLY...PARTICULARLY ONCE THE CYCLONE STARTS TO DEVOLVE AND  
THE WAVE(S) BEGIN TO EJECT INTO THE PACIFIC NORTHWEST. WHILE ALL  
THE MODELS AGREE WITH THE BIG PICTURE -- NOTABLE HEIGHT FALLS  
SPREADING INTO THE REGION ON MONDAY -- DIFFERENCES EXIST WITH THE  
INTERNAL STRUCTURE (NUMBER OF SHORTWAVES, EXACT PLACEMENT).  
HOWEVER...ENSEMBLE SPAGHETTI PLOTS OF CERTAIN MASS FIELDS SHOW  
AVAILABLE OPERATIONAL MODELS WELL WITHIN THE SPREAD OF THE MOST  
EXTREME MEMBERS. WITHOUT ANY SUBSTANTIAL INDICATION THAT A GIVEN  
MODEL HAS A SYSTEMATIC BIAS...
PREFER A GENERAL MODEL BLEND IN THIS  
CASE TO ACCOUNT FOR THE FULL RANGE OF POSSIBILITIES.  
 
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
LAMERS  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page