797  
FXUS10 KWNH 161616  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1115 AM EST FRI FEB 16 2018  
 
VALID FEB 16/1200 UTC THROUGH FEB 20/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z GFS/NAM EVALUATION WITH PRELIMINARY MODEL PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT  
RANGE FORECASTS.  
 
 
LOW MOVING FROM THE SOUTHEAST OFFSHORE NEW ENGLAND  
AND ITS ASSOCIATED SHORTWAVE ALOFT  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-UKMET BLEND; CONFIDENCE AVERAGE  
 
THE GUIDANCE SHOWS GOOD AGREEMENT WITH THE PARENT SHORTWAVE  
THROUGH TONIGHT. THEREAFTER, THE 00Z ECMWF BECOMES A BIT MORE  
AMPLIFIED THAN THE OTHER GUIDANCE WITH THE SHORTWAVE WHILE THE 12Z  
NAM ULTIMATELY IS THE WEAKEST (FAR FROM ITS TYPICAL BIAS). THIS  
MAY NOT BE A BAD MOVE ON SATURDAY AS THE SHORTWAVE COULD GAIN SOME  
AMPLITUDE AS IT MOVES UNDER THE BASE OF THE STRONG MID-LEVEL  
VORTEX OVER NUNAVUT. HOWEVER, THE SHORTWAVE MOVES THROUGH AN  
INCREASINGLY ZONAL/CONFLUENT FLOW THEREAFTER WHICH SHOULD LEAD TO  
A WEAKER/BROADER SHORTWAVE WITH TIME. AT THE SURFACE, THE 00Z  
UKMET IS THE MOST NORTHWESTERLY AND HAS MINORITY 00Z GLOBAL  
ENSEMBLE SUPPORT SO DID NOT CONSIDER IT VIABLE. HOWEVER, THE REST  
OF THE GUIDANCE IS WITHIN THE ENSEMBLE SPREAD AND COULD NOT BE  
EASILY DISCOUNTED. CONSIDERING THE ABOVE, A COMPROMISE OF THE 00Z  
ECMWF, 12Z GFS, 12Z NAM, AND 00Z CANADIAN IS PREFERRED WITH  
AVERAGE CONFIDENCE.  
 
UPPER TROUGH DIGGING INTO THE WEST  
PRESSURE PATTERN IN THE PLAINS/MIDWEST  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON NAM-BLEND; CONFIDENCE ABOVE AVERAGE  
 
AS USUAL, THE 12Z NAM IS THE STRONGEST WITH THE UPPER TROUGH --  
ITS USUAL BIAS. AS THE SURFACE, ITS LOW DEPICTION IN IA LATE  
TUESDAY FALLS OUTSIDE THE 00Z GLOBAL ENSEMBLE SPREAD. A  
COMPROMISE OF THE 12Z GFS, 00Z UKMET, 00Z ECMWF, AND 00Z CANADIAN  
IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE.  
 
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ROTH  

 
 
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