290  
FXUS10 KWNH 261851  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
150 PM EST FRI JAN 26 2018  
 
VALID JAN 26/1200 UTC THRU JAN 30/0000 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 THE SOUTHERN  
PLAINS TODAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS HANDLE THE SYSTEM SIMILARLY AS IT MOVES EAST AND  
WEAKENS WITH TIME.  
 
   
..LARGE UPPER TROUGH MOVING THROUGH THE WESTERN/CENTRAL U.S
 
 
...SURFACE LOW NEAR THE U.S./CANADIAN BORDER MOVING EAST WITH  
TRAILING COLD FRONT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: 12Z NAM/GFS/ECMWF  
CONFIDENCE: AVERAGE  
 
THE 12Z RUNS OF THE NCEP GUIDANCE HAVE ADJUSTED TOWARDS A  
CONSENSUS SOLUTION SUGGESTED BY THE OVERNIGHT ENSEMBLES AND THEY  
CLUSTERED PRETTY WELL WITH OTHER OPERATIONAL RUNS. THE 26/00Z  
UKMET WAS ON THE FLATTER/FASTER SIDE OF THE GUIDANCE BUT IT WAS  
NOT NEARLY AS FAST/FLAT AS IT WAS ON ITS WEDNESDAY NIGHT/THURSDAY  
MORNING RUNS. GIVEN GOOD RUN TO RUN CONSISTENCY BY THE CANADIAN,  
IT THIS BETTER CLUSTERING LEFT THE 00Z CANADIAN A BIT OUT OF  
PHASE. FOR THE MOMENT, WILL REMOVE IT FROM THE PREFERENCE PENDING  
ARRIVAL OF THE 12Z GUIDANCE.  
 
 
...LOW AMPLITUDE MID-LEVEL SHORTWAVE NEARING THE PACIFIC NORTHWEST  
 
LATE TONIGHT WITH ACCOMPANYING SURFACE LOW...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: 12Z GFS/ECMWF BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
ENSEMBLE SCATTER LOW PLOTS STILL SUPPORT A 12Z GFS/ECMWF BLEND  
WITH THE SURFACE LOW AS IT...AND THE ASSOCIATED MID LEVEL  
WAVE...APPROACHES THE PACIFIC NORTHWEST AND THEN HEADS TOWARDS THE  
SOUTHEAST. THE UKMET ALSO OFFERED A VIABLE SOLUTION...PRIMARILY  
ON DAY 1. THE 12Z NAM WAS NOT QUITE AS FAR SOUTH WITH THE WAVE AS  
IT HAD BEEN IN PREVIOUS RUNS...BUT IT WAS STILL ON THE SOUTH SIDE  
OF THE ENVELOPE OF SOLUTIONS AND IT HAD A STRONGER VORTICITY  
CENTER BY THE TIME THE VORT REACHED THE MEAN LONG WAVE POSITION.  
FOR THE REMAINING MODELS, THE LATITUDINAL DIFFERENCES WERE PRETTY  
SMALL BUT INCREASE LATE ON DAY 3 WHEN THE NAM AND UKMET BECAME  
SLOW/DEEP OUTLIER COMPARED WITH OTHER MODEL RUNS.  
 
   
..LARGE CLOSED LOW APPROACHING BRITISH COLUMBIA LATE SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: NON UKMET MODEL BLEND  
CONFIDENCE: AVERAGE  
 
THE 26/00Z CANADIAN DEVELOPED A DOUBLE-BARRELED LOOK TO ITS  
MID/UPPER LEVEL SYSTEM CENTERED AROUND 145W...WHICH LED TO SEVERAL  
PERIODS WHERE THE CANADIAN WAS SOME 200 NMI NORTH OF OTHER MODEL  
GUIDANCE. GIVEN THE ADJUSTMENTS MADE BY THE 12Z CANADIAN...THINK  
THAT THE CANADIAN CAN ONCE AGAIN BE INCORPORATED INTO THE MODEL  
BLEND. THAT LEAVES THE 12Z UKMET AS AN OUTLIER WITH THIS SYSTEM.  
OTHERWISE...THE REMAINING OPERATIONAL MODEL RUNS TENDED TO CLUSTER  
FAIRLY TIGHTLY WITH THE ENSEMBLE MEANS FROM THE GEFS AND ECMWF.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
BANN  
 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page