961  
FXUS10 KWNH 251848  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
148 PM EST THU JAN 25 2018  
 
VALID JAN 25/1200 UTC THRU JAN 29/0000 UTC  
 
..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
   
..12Z MODEL EVALUATION ALONG WITH FINAL PREFERENCES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...MID-LEVEL SHORTWAVE WEAKENING NORTHEASTWARD FROM WEST TEXAS  
TODAY/TONIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.  
 
   
..LARGE UPPER TROUGH MOVING THROUGH THE WESTERN U.S. TODAY
 
 
...SURFACE LOW NEAR THE U.S./CANADIAN BORDER MOVING EAST WITH  
TRAILING COLD FRONT FRIDAY THROUGH THE WEEKEND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM / 12Z ECMWF / 12Z CMC BLEND  
CONFIDENCE: AVERAGE  
 
THE 12Z GFS CONTINUES TO APPEAR FASTER THAN THE MODEL CONSENSUS  
WITH THE PROGRESSION OF THE 500 MB TROUGH MOVING ACROSS THE UPPER  
MISSISSIPPI VALLEY EARLY SATURDAY MORNING AND WITH ENERGY IN THE  
BASE OF THE TROUGH NEAR KANSAS AND MISSOURI. WHILE THE 12Z UKMET  
TRENDED TOWARD THE CONSENSUS, CERTAINLY COMPARED TO ITS 00Z CYCLE,  
IT IS A BIT SLOWER THAN IDEAL WITH THE TROUGH PROGRESSION ACROSS  
THE MISSISSIPPI VALLEY. A 12Z NAM/ECMWF/CMC BLEND APPEARS MOST  
FAVORABLE WITH THIS SYSTEM.  
 
THIS PREFERENCE ALSO APPLIES ACROSS THE GULF COAST WHERE THE 12Z  
GFS IS LESS AGGRESSIVE WITH MOISTURE RETURN INTO THE CENTRAL GULF  
COAST REGION ON SATURDAY. A FRONTAL WAVE IN THE GULF OF MEXICO  
APPEARS TO BE REPRESENTED IN THE DETERMINISTIC GUIDANCE BY SUNDAY  
MORNING. HOWEVER, THE 12Z GFS IS FASTER WITH THIS FEATURE AND IS  
STRONGER THAN THE REMAINING DETERMINISTIC GUIDANCE AND ONLY WEAKLY  
SUPPORTED IN THE ENSEMBLE DATA. THEREFORE, A 12Z NAM/ECMWF/CMC  
BLEND APPEARS A BETTER FIT FOR THIS ENTIRE SYSTEM, FROM CANADA TO  
THE GULF COAST.  
 
...LOW AMPLITUDE MID-LEVEL SHORTWAVE NEARING THE PACIFIC NORTHWEST  
LATE FRIDAY NIGHT WITH ACCOMPANYING SURFACE LOW...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS / 12Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
ENSEMBLE SCATTER LOW PLOTS SUPPORT A 12Z GFS, 12Z ECMWF, 12Z CMC  
AND 12Z UKMET BLEND WITH THE SURFACE LOW AS IT APPROACHES THE  
PACIFIC NORTHWEST. THERE IS MODERATELY GOOD AGREEMENT IN THE  
ENSEMBLE DATA TO SUPPORT THIS PREFERENCE. THE 12Z NAM IS FARTHER  
SOUTH WHILE THE 00Z UKMET IS STRONGER AND NORTHWARD. AS THE  
SHORTWAVE MOVES INLAND, THE 12Z GFS/ECMWF APPEAR REASONABLY WELL  
CLUSTERED WITH THE ENSEMBLE MEANS.  
 
   
..LARGE CLOSED LOW APPROACHING BRITISH COLUMBIA LATE SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
ENSEMBLE DATA IS REASONABLY CLUSTERED WITH THIS NEXT SYSTEM TO  
IMPACT THE WEST COAST, BUT THE 00Z UKMET APPEARS A LOW PROBABILITY  
SOLUTION GIVEN ITS PLACEMENT ON THE SLOW EDGE OF GEFS/ECMWF/CMC  
ENSEMBLE MEMBERS. THE 12Z ECMWF/UKMET/CMC ADJUSTED SLIGHTLY, WITH  
THE 12Z UKMET CLOSE NOW ENOUGH TO THE CONSENSUS TO INCLUDE IN THE  
PREFERENCE. CONFIDENCE IS ONLY AVERAGE CONSIDERING THE LONGER, 84  
HOUR FORECAST RANGE.  
 
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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