654  
FXUS10 KWNH 291604  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1103 AM EST MON JAN 29 2018  
 
VALID JAN 29/1200 UTC THRU FEB 02/0000 UTC  
   
.SEE NOUS42 KWNO (ADMNFD) FOR UPPER AIR INGEST STATUS
 
 
12Z PRELIMINARY MODEL EVALUATION WITH PREFERENCES/CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
 
EVOLVING LONG WAVE TROUGH OVER THE EASTERN U.S. BY TUESDAY  
SURFACE LOW EVOLUTION OFFSHORE THE MID-ATLANTIC/NEW ENGLAND  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: BLEND OF THE 29/12Z GFS...29/00Z EC MEAN/UKMET  
CONFIDENCE: AVERAGE  
 
SOME SUBTLE YET STILL IMPORTANT DIFFERENCES LINGER OVER THE  
SURFACE RESPONSE OUT OVER THE WESTERN NORTH ATLANTIC AND THE  
RESULTING IMPACTS ALONG THE COAST. THE 29/00Z ECMWF ENSEMBLE  
MEMBERS WERE MORE AMPLIFIED AND A BIT FASTER THAN THE GEFS AND THE  
OPERATIONAL ECMWF/GFS WITH THE FIRST PIECE OF ENERGY MOVING  
THROUGH THE NORTHERN STREAM TROUGH BY 30/12Z...AND THEN HOLDS THE  
TROUGH BACK A BIT MORE AS A SECOND PIECE OF SHORTWAVE ENERGY MOVES  
THROUGH SOME 12 TO 18 HOURS LATER.  
 
GIVEN SATELLITE PRESENTATION AND RAOB SAMPLING...THINK THAT THE  
SECOND PIECE OF SHORTWAVE ENERGY MAY BE HANDLED BETTER BY THE  
29/00Z GFS/UKMET AND ECMWF ENSEMBLE MEAN. THE OPERATIONAL  
CANADIAN AND THE NAEFS LOOKED TO BE TOO WEAK WITH THE WAVE  
AMPLITUDE BY 30/12Z. WHILE THESE DIFFERENCES EXIST...THE OVERALL  
CLUSTERING HAS IMPROVED OVER THE PAST FEW RUNS.  
 
LOW OVER CANADA MOVING EASTWARD AND IMPACTS IN NORTHERN U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: 29/00Z ECMWF AND 29/12Z GFS BLEND  
CONFIDENCE: AVERAGE  
 
THE GFS HAS HAD A TENDENCY TO WRAP UP THE SYSTEM TOO MUCH AS IT  
MOVES ACROSS CANADA OVER THE PAST FEW RUNS. THE 12Z RUN ALSO  
LOOKED TO BE TOO WEAK...DEEPENING THE SURFACE LOW TO 981  
MB...WHICH WAS SOME 4 TO 7 MB DEEPER THAN OTHER OPERATIONAL AND  
ENSEMBLE FORECASTS VALID AT 30/21Z. THE RESULT WAS LOWER SURFACE  
PRESSURES ALONG THE INTERNATIONAL BORDER. THE GFS PLACEMENT WAS  
PRETTY WELL SUPPORTED. SO A BLEND OF THE ECMWF AND GFS SHOULD  
WORK FOR POSITION...ALTHOUGH HEDGING SOMEWHAT TOWARDS THE ECMWF  
WOULD HELP MITIGATE DIFFERENCES IN STRENGTH WITH RESPECT TO THE  
MID LEVEL TROUGH AND SURFACE LOW. SPAGHETTI PLOTS OF MID LEVEL  
HEIGHTS SHOWED GOOD CLUSTERING...WITH THE EXCEPTION OF THE NAEFS  
WHICH ENDED UP HAVING A FEW MEMBERS WHICH WERE STRONG/FAST  
OUTLIER.  
 
 
SHORTWAVE APPROACHING THE PACIFIC NORTHWEST LATE TONIGHT AND  
MOVINNG  
INLAND THROUGH TUESDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
A LARGE AREA OF LOW PRESSURE...ALOFT AND AT THE SURFACE...NEAR 50N  
145W THIS MORNING WILL BE FILLING AS IT APPROACHES THE WEST COAST  
OF NORTH AMERICA LATER TONIGHT OR EARLY TUESDAY MORNING.  
SHORTWAVE ENERGY ALOFT ACCOMPANIED BY A SURFACE COLD FRONT IS  
EXPECTED TO PIVOT AROUND THE SOUTHERN PERIPHERY OF THE LARGE UPPER  
LOW AND AFFECT THE PACIFIC NORTHWEST FROM LATER TONIGHT INTO EARLY  
TUESDAY. MODEL AGREEMENT WAS GOOD WITH THE OVERALL SCENARIO.  
THINK A GENERAL MODEL COMPROMISE WILL TAKE CARE OF ANY MINOR  
DIFFERENCES PERTAINING TO STRENGTH OR POSITION.  
 
BANN  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 

 
 
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