971  
FXUS10 KWNH 091849  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
249 PM EDT MON OCT 09 2017  
 
VALID OCT 09/1200 UTC THRU OCT 13/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
   
..12Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...SHORTWAVE EJECTING INTO THE PLAINS TONIGHT AND THEN  
ACCELERATING TO THE NORTHEAST U.S. BY THURSDAY...  
...COLD FRONT PUSHING SOUTH DOWN THE HIGH PLAINS TODAY AND  
TUESDAY...  
...SURFACE LOW TRACKING FROM THE SOUTHERN PLAINS TODAY INTO THE  
OHIO VALLEY ON WEDNESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECWMF/NAM/UKMET BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE 12Z GFS STANDS OUT AS FASTER THAN THE REMAINING  
DETERMINISTIC/ENSEMBLE GUIDANCE REGARDING THE MID-LEVEL SHORTWAVE  
AS IT TRACKS INTO THE OHIO VALLEY. THE 12Z NAM IS ALSO ON THE FAST  
SIDE...BUT HAS BEEN JOINED BY THE 12Z ECMWF/UKMET/CMC...BUT ALL  
SHOWING SLOWER THAN THE 12Z GFS. GIVEN A BLEND OF THE LATEST  
ENSEMBLE MEANS IS NEAR A BLEND OF THE 12Z ECMWF/NAM/UKMET...THAT  
WILL BE THE PREFERENCE. THE 12Z CMC REMAINS A BIT SOUTH OF THE  
ENSEMBLE MEANS WITH THE 850 MB LOW CROSSING THE MISSISSIPPI SO IT  
IS NOT INCLUDED IN THE PREFERENCE.  
 
...UPPER TROUGH DIGGING SOUTHEAST INTO THE PACIFIC NORTHWEST ON  
TUESDAY WITH LEE CYCLOGENESIS IN THE VICINITY OF MONTANA...   
..COLD FRONT CROSSING THE NORTHWEST
 
REACHING THE NORTHERN  
PLAINS ON THURSDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS/12Z ECMWF BLEND  
CONFIDENCE: AVERAGE  
 
DIFFERENCES WITH THIS SYSTEM BEGIN TO SHOW UP STARTING LATE  
WEDNESDAY WITH THE 12Z NAM AND UKMET LIFTING THE LEADING SHORTWAVE  
TROUGH MORE QUICKLY INTO SWRN CANADA THAN THE REMAINING MODELS.  
THE 12Z CMC TRENDED STRONGER WITH THE LEADING SHORTWAVE AND A BIT  
SLOWER BUT NOT QUITE TO THE EXTENT OF THE PREFERRED 12Z GFS/ECMWF.  
THE LATEST ENSEMBLE MEANS SUPPORT A SOLUTION CLOSER TO A BLEND OF  
THE 12Z GFS/ECMWF GIVEN THEIR RETENTION OF A CLOSED LOW OVER  
SASKATCHEWAN ON THURSDAY.  
 
...SORTWAVE DROPPING SOUTH TOWARD THE PACIFIC NORTHWEST LATE  
THURSDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM...12Z GFS...12Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE 12Z NAM...12Z GFS AND 12Z ECMWF ARE IN GOOD AGREEMENT WITH A  
SECOND SHORTWAVE NEARING THE PACIFIC NORTHWEST ON THURSDAY...IN  
THE WAKE OF THE FIRST SHORTWAVE LIFTING NORTHEASTWARD OVER S-CNTRL  
CANADA THURSDAY NIGHT. THE LATEST ENSEMBLE SPAGHETTI HEIGHTS OF  
546 DAM SHOW THE 12Z UKMET/CMC REMAIN DISPLACED  
WEST/EAST...RESPECTIVELY...WITH THE WAVE DESPITE HAVING TRENDED  
TOWARD THE PRELIMINARY WPC PREFERENCE. SINCE THE 12Z UKMET/CMC LIE  
TOWARD THE EDGES OF THE ENSEMBLE GUIDANCE...A 12Z NAM/GFS/ECMWF  
BLEND APPEARS TO BE A GOOD FIT FOR THIS SYSTEM.  
 
   
..POST-TROPICAL CYCLONE NATE
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 12Z NAM BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE ANALYZED 18Z POSITION OF NATE WAS OVER CNTRL NY...WITH THE  
LATEST DETERMINISTIC MODELS CLOSE TO THIS POSITION. HOWEVER...THE  
12Z NAM BECOMES NORTH OF THE DETERMINISTIC AND TIGHTLY CLUSTERED  
ENSEMBLE CONSENSUS STARTING NEAR 00Z/10. GOOD MODEL AGREEMENT  
EXISTS FOR A NON 12Z NAM BLEND WITH THE REMNANT LOW OF NATE.  
 
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