139  
FXUS10 KWNH 041858  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
158 PM EST SUN FEB 04 2018  
 
VALID FEB 04/1200 UTC THRU FEB 08/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
   
..12Z MODEL EVALUATION WITH FINAL PREFERENCES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...SHORTWAVE TRACKING FROM THE UPPER MISSISSIPPI VALLEY INTO THE  
OHIO VALLEY TODAY...  
...SURFACE LOW TRACKING NORTHEAST FROM THE SOUTHEASTERN U.S.  
TODAY, STRENGTHENING ALONG THE NEW ENGLAND COAST THROUGH EARLY  
MONDAY MORNING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS HAVE CONVERGED SINCE YESTERDAY TO A COMMON IDEA WITH  
ONLY MINOR DIFFERENCES NOTED IN THE LATEST GUIDANCE. A GENERAL  
MODEL BLEND IS PREFERRED TO SMOOTH OUT ANY REMAINING DIFFERENCES.  
 
...WEAK 700 MB SHORTWAVE TRACKING ACROSS THE CENTRAL PLAINS INTO  
THE MIDWEST ON MONDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-12Z NAM BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE 12Z NAM IS SLIGHTLY SHARPER/DEEPER/SLOWER WITH THE 700 MB  
SHORTWAVE AS IT REACHES THE MISSISSIPPI VALLEY NEAR 00Z/06. THE  
REMAINING DETERMINISTIC/ENSEMBLE CONSENSUS SUPPORTS A NON-12Z NAM  
BLEND FOR THIS SYSTEM. THE REMAINING 12Z GUIDANCE CONTINUES TO  
SUPPORT A NON-12Z NAM BLEND FOR THIS SYSTEM.  
 
...MID-LEVEL SHORTWAVE CROSSING THE NORTHWEST TODAY, WITH  
ADDITIONAL ENERGY AMPLIFYING ACROSS THE FOUR CORNERS REGION  
TUESDAY EVENING AND INTO THE PLAINS ON WEDNESDAY...  
...NORTHERN STREAM SHORTWAVE CROSSING THE UPPER MISSISSIPPI VALLEY  
ON WED WITH  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM / 12Z GFS / 12Z ECMWF BLEND  
CONFIDENCE: AVERAGE  
 
THE 00Z/12Z UKMET IS FASTER WITH THE NORTHERN AND SOUTHERN STREAM  
SHORTWAVES ASSOCIATED WITH THIS SYSTEM, NOTED AS EARLY AS TUESDAY  
MORNING. THE EFFECT IS FOR THE FRONT IN THE SOUTHERN PLAINS TO BE  
DISPLACED FARTHER SOUTH IN THE 00Z/12Z UKMET COMPARED TO THE  
REMAINING GUIDANCE. THE 12Z CMC 850 MB LOW IS LESS DEVELOPED AND  
DISPLACED WESTWARD BY 12Z/07. THE 12Z NAM/12Z GFS AND 12Z ECMWF  
ARE IN REASONABLE AGREEMENT AND ARE SUPPORTED BY THE LATEST  
ENSEMBLE MEANS. THE 12Z ECMWF DID SHIFT FASTER WITH THE NORTHERN  
STREAM WAVE AND SLOWED WITH THE SOUTHERN STREAM WAVE RELATIVE TO  
ITS PREVIOUS RUN BUT THE 12Z ECMWF IS WITHIN THE RELATIVELY TIGHT  
ENSEMBLE SPREAD WHICH IS MINOR ALOFT. ENSEMBLE SPREAD IS MODEST AT  
THE SURFACE.  
 
...SHORTWAVE APPROACHING THE PACIFIC NORTHWEST LATE WEDNESDAY  
NIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECMWF/UKMET/CMC BLEND  
CONFIDENCE: AVERAGE  
 
THE ENSEMBLE MEANS ARE IN GOOD AGREEMENT AND SHOW THE 00Z CMC IS  
TOO FAST WITH THE SHORTWAVE FORECAST TO NEAR THE PACIFIC NORTHWEST  
00Z/08 BUT THE 12Z RUN SLOWED TOWARD THE BETTER CONSENSUS. THE 12Z  
ECMWF/UKMET/CMC ARE CLOSEST TO THE ENSEMBLE MEANS WHILE THE 12Z  
NAM AND 12Z GFS ARE SLOWER. HOWEVER, ENSEMBLE SPAGHETTI HEIGHT  
SPREAD IS LARGE SO CONFIDENCE IN THIS PREFERENCE IS ONLY AVERAGE  
GIVEN THE 3 DAY TIME FRAME AND POTENTIAL FOR FUTURE CHANGES IN THE  
GUIDANCE.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 

 
 
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