331  
FXUS10 KWNH 241849  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
148 PM 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 MODEL EVALUATION ALONG WITH FINAL 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 12Z-CMC 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 12Z ECMWF HAS BEEN A BIT SLOWER WITH SOME  
TRENDS TO BE FASTER OVER ITS PAST FEW RUNS, INCLUDING THE 12Z  
ECMWF. THE 12Z NAM IS A BIT FASTER AS WELL WHEN COMPARED TO THE  
ECMWF BUT NOT AS FAST AS THE 12Z GFS.  
 
THE 12Z UKMET ADJUSTED AWAY FROM ITS PREVIOUS OUTLIER 00Z SOLUTION  
WHICH HAD A SIGNIFICANTLY DEEPER TROUGH BY 00Z/28 AND SO NOW THE  
12Z UKMET TIMING IS CONSIDERED REASONABLE, 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. THE 12Z ECMWF IS CONSIDERED FAVORABLE WHEN  
BLENDED WITH THE 12Z UKMET AND SLIGHTLY FASTER 12Z NAM ALONG WITH  
THE 12Z GFS. THE 12Z NAM ENDS UP FLATTER WITH THE TROUGH AXIS NEAR  
00Z/28 COMPARED TO THE REMAINING MODEL CONSENSUS AND ENSEMBLE  
DATA. THE 12Z CMC TRENDED FASTER AND WILL NOT BE INCLUDED IN THE  
PREFERENCE AS WAS THE 00Z CMC.  
 
THEREFORE, NO SINGLE MODEL IS PREFERRED, BUT PERHAPS A BLEND OF  
THE 12Z NAM/GFS/ECMWF/UKMET 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 12/00Z ECMWF ARE IN LINE WITH THE LATEST  
ENSEMBLE DATA EXCEPT THE ECMWF BECOMES A STRONGER NEAR-OUTLIER  
WITH RIDGING OFF OF THE WEST COAST BY 00Z/28. THE 12/00Z 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 12/00Z 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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