829  
FXUS10 KWNH 240502  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
102 AM EDT WED OCT 24 2018  
 
VALID OCT 24/0000 UTC THRU OCT 27/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z NAM/GFS EVALUATION...WITH PRELIMINARY PREFERENCES AND  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
OVERALL PREFERENCE: BLEND OF 00Z GFS/12Z ECMWF/12Z UKMET  
CONFIDENCE: AVERAGE  
 
ANOMALOUS MID-UPPER LEVEL RIDGING WILL BUILD INTO THE SOUTHWESTERN  
U.S. THROUGH FRIDAY NIGHT WHILE QUASI-ZONAL FLOW FOCUSES NORTH OF  
THE RIDGE INTO THE PACIFIC NORTHWEST. MEANWHILE, NORTHERN STREAM  
TROUGHING THAT IS CURRENTLY OVER THE NORTHEAST WILL SLOWLY DEPART  
THE REGION THROUGH FRIDAY BUT SOUTHERN STREAM TROUGHING CURRENTLY  
OUT WEST WILL AMPLIFY AND SLOWLY TRANSLATE TO JUST EAST OF THE  
MISSISSIPPI RIVER BY SATURDAY MORNING AS A NUMBER OF SHORTWAVES  
TRAVERSE ATOP THE WESTERN RIDGE THROUGH THE PLAINS.  
 
AT THE SURFACE, TWO MAIN COLD FRONTS WILL HAVE THE GREATEST  
INFLUENCE ON THE SENSIBLE WEATHER THROUGH FRIDAY. A COLD FRONT  
WILL REACH THE PACIFIC NORTHWEST LATE TODAY AND STALL TEMPORARILY  
ALONG THE WASHINGTON COAST UNTIL ANOTHER SURFACE WAVE MOVES  
THROUGH SENDING THE COLD FRONT INTO SOUTHERN OREGON FOR FRIDAY  
NIGHT. THE OTHER FRONT WILL DEVELOP AS A SURFACE LOW ORGANIZES  
ALONG AN EXISTING FRONTAL BOUNDARY IN THE GULF OF MEXICO. THE  
SURFACE LOW IS EXPECTED TO HUG THE CENTRAL GULF COAST ON THURSDAY  
WHILE TRACKING EAST BEFORE REDEVELOPING ALONG THE SOUTHEASTERN  
U.S. COAST AND TRACKING NORTHWARD ALONG THE EAST COAST FRIDAY  
NIGHT INTO SATURDAY.  
 
REGARDING MODEL DIFFERENCES, THE ENSEMBLES ARE IN DECENT AGREEMENT  
AND SUPPORT THE 00Z GFS, 12Z ECMWF AND 12Z UKMET WITH THE 00Z NAM  
SURFACE LOW NEARLY OUTSIDE OF THE ENSEMBLE SPREAD AND 12Z CMC ON  
THE SOUTHERN EDGE. WHILE MOISTURE FLUX INTO THE PACIFIC NORTHWEST  
MAY NOT DIFFER ALL THAT GREATLY, STAYING CLOSER TO THE 00Z GFS/12Z  
UKMET/12Z ECMWF IS PREFERRED.  
 
IN THE GULF OF MEXICO, THE 12Z CMC IS SLOWER/WEAKER WITH HURRICANE  
WILLA ALONG THE MEXICAN COAST WITH THE OTHER DETERMINISTIC  
GUIDANCE IN GOOD AGREEMENT WITH EACH OTHER AND OBSERVATIONS AT  
00Z/24. THE SURFACE LOW TRACK ALONG THE GULF AND EAST COAST,  
ENSEMBLES AGREE BEST WITH THE 00Z GFS, 12Z ECMWF AND 12Z UKMET.  
 
IN THE NORTHERN PLAINS/SOUTH-CENTRAL CANADA ON FRIDAY, MODEL  
AGREEMENT WITH A CLOSED LOW IS POOR, WITH ONLY THE 00Z NAM  
APPEARING OUT OF TOLERANCE WITH THE ENSEMBLES AND REMAINING  
DETERMINISTIC MODELS. TRENDS ARE INCONCLUSIVE AND THE ENSEMBLE  
MEANS ARE BETWEEN THE 00Z GFS/12Z ECMWF/12Z UKMET (NORTH) AND 12Z  
CMC (SOUTH). THE PREFERENCE IS TO GO BETWEEN THE TWO FOR NOW BUT  
CONFIDENCE IS REDUCED.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 

 
 
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