868  
FXUS10 KWNH 271615  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1114 AM EST THU FEB 27 2020  
 
VALID FEB 27/1200 UTC THRU MAR 02/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z NAM/GFS EVALUATION WITH MODEL PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
CONUS AND CANADA  
~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THREE ARE THREE SYSTEMS OF NOTE ACROSS THE US AND CANADA DURING  
THE PERIOD.  
 
CONCERNING THE EXITING SURFACE SYSTEM AND CLOSED MID LEVEL LOW  
OVER QUEBEC AND NORTHERN NEW ENGLAND, THE 12Z NAM/GFS ARE CLOSE TO  
THE CONSENSUS WITH THE PLACEMENT OF THE VARIOUS REDEVELOPMENTS OF  
SURFACE LOWS FROM NEW BRUNSWICK/NOVA SCOTIA AND FURTHER SOUTH  
THROUGH 01/00Z. AFTER THAT TIME, THERE IS SOME MODEL SPREAD  
CONCERNING THE PLACEMENT OF THE SURFACE LOWS ALONG THE EXTENDED  
FRONTAL BOUNDARY, BUT BY THAT TIME THE SENSIBLE WEATHER EFFECTS ON  
THE CONUS ARE LIMITED.  
 
THE SECOND SYSTEM IS THE SHORT WAVE THAT COMES ASHORE OVER WA  
STATE AROUND 29/00Z. UNLIKE THE PAST FEW CYCLES, THERE IS BETTER  
AGREEMENT ON THE TIMING OF THE SHORT WAVE AS IT TRACKS INTO  
WESTERN ONTARIO BY THE END OF THE PERIOD. THE 00Z ECMWF/CMC ARE  
SLOWER THAN THE CONSENSUS, BUT HAVING BEEN SPEEDING UP IN RECENT  
RUNS AS THE UPSTREAM CLOSED LOW OVER QUEBEC MOVES EASTWARD. FOR  
THIS SYSTEM, THE 12Z NAM/GFS MAY FORM A BETTER STARTING POINT.  
 
FINALLY, FOR THE SHORT WAVE NEAR 45N 137W AT 23/12Z, THERE IS GOOD  
MODEL AGREEMENT AS IT EVOLVES INTO A LONG WAVE TROUGH OVER CA  
BEFORE CLOSING OFF BY 02/00. WHILE THERE ARE SOME MINOR TIMING  
DIFFERENCES LATE IN THE PERIOD, THERE IS ENOUGH CLUSTERING TO  
RECOMMEND A GENERAL MODEL BLEND HERE.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
HAYES  
 

 
 
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