915  
FXUS10 KWNH 291852  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
151 PM 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 FINAL 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/UKMET...29/00Z EC MEAN  
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  
29/12Z GFS/UKMET AND 29/00Z ECMWF ENSEMBLE MEAN. THE OPERATIONAL  
CANADIAN AND THE NAEFS STILL 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: 29/12Z ECMWF/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 STRONG...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. GIVEN GOOD RUN TO RUN CONSISTENCY FOR THE  
UKMET AND ECMWF AT 12Z...A BLEND OF THE 12Z ECMWF AND GFS SHOULD  
WORK FOR POSITION...ALTHOUGH HEDGING SOMEWHAT TOWARDS THE ECMWF  
WOULD HELP MITIGATE DIFFERENCES IN STRENGTH AT THE SURFACE AND  
ALOFT. 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 OUTLIERS.  
 
 
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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page