310  
FXUS10 KWNH 241648  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1148 AM EST WED JAN 24 2018  
 
VALID JAN 24/1200 UTC THRU JAN 28/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
   
..12Z NAM/GFS EVALUATION ALONG WITH PRELIMINARY PREFERENCES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...QUICK MOVING SHORTWAVE REACHING THE MID-ATLANTIC COAST  
TONIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.  
 
...MID-LEVEL SHORTWAVE WEAKENING NORTHEASTWARD FROM NORTHERN  
MEXICO THROUGH FRIDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.  
 
...LARGE UPPER TROUGH MOVING THROUGH THE WESTERN U.S.  
TODAY/TOMORROW...  
...SURFACE LOW NEAR THE U.S./CANADIAN BORDER MOVING EAST WITH  
TRAILING COLD FRONT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 00Z UKMET BLEND  
CONFIDENCE: AVERAGE  
 
MORE SIGNIFICANT DIFFERENCES APPEAR AROUND 00Z/27 CONCERNING THE  
COLD FRONTAL TIMING THROUGH THE MISSISSIPPI VALLEY. THE 12Z GFS  
CONTINUES TO BE FASTER WITH THE OVERALL UPPER TROUGH PROGRESSION  
ACROSS THE CENTER OF THE COUNTRY, BUT HAS TRENDED SLOWER SINCE  
TUESDAY. MEANWHILE, THE 00Z ECMWF HAS BEEN A BIT SLOWER WITH SOME  
TRENDS TO BE FASTER OVER ITS PAST FEW RUNS. THE 12Z NAM IS A BIT  
FASTER AS WELL WHEN COMPARED TO THE 00Z ECMWF BUT NOT AS FAST AS  
THE 12Z GFS.  
 
GIVEN THE 00Z UKMET BECOMES A DEEPER OUTLIER WITH THE BASE OF THE  
TROUGH BY 00Z/28, IT IS NOT PREFERRED. THE 12Z GFS IS THE ONLY  
MODEL THAT DOES NOT SHOW STRONGER VORTICITY ENERGY IN THE BASE OF  
THE UPPER TROUGH NEAR 12Z/27 OVER THE CENTRAL PLAINS GIVEN ITS  
FASTER PROGRESSION. HOWEVER, THE 00Z ECMWF IS CONSIDERED TOO  
SLOW/STRONG WITH THIS FEATURE. THE 12Z NAM ENDS UP FLATTER WITH  
THE TROUGH AXIS NEAR 00Z/28 COMPARED TO THE REMAINING MODEL  
CONSENSUS AND ENSEMBLE DATA.  
 
THEREFORE, NO SINGLE MODEL IS PREFERRED, BUT PERHAPS A BLEND OF  
THE 12Z NAM, 12Z GFS, 00Z ECMWF, 00Z CMC WILL BE ABLE TO SMOOTH  
OUT INDIVIDUAL ISSUES SEEM IN THE DETERMINISTIC GUIDANCE.  
 
...LOW AMPLITUDE MID-LEVEL SHORTWAVE NEARING THE PACIFIC NORTHWEST  
LATE FRIDAY NIGHT WITH ACCOMPANYING SURFACE LOW...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM/GFS BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE 12Z NAM/GFS AND 00Z ECMWF ARE IN LINE WITH THE LATEST ENSEMBLE  
DATA EXCEPT THE 00Z ECMWF BECOMES A STRONGER NEAR-OUTLIER WITH  
RIDGING OFF OF THE WEST COAST BY 00Z/28. THE 00Z ECMWF IS  
OTHERWISE USABLE UNTIL AROUND 00Z/28 GIVEN ITS MOISTURE AXIS IS  
ORIENTED AWAY FROM THE REMAINING MODEL CONSENSUS. THE SURFACE LOW  
DEPICTED IN THE ENSEMBLE DATA IS REPRESENTED BY A BLEND OF THE 12Z  
NAM/GFS AND 00Z ECMWF.  
 
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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