475   
FXUS10 KWNH 191901  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
201 PM EST TUE NOV 19 2019  
  
VALID NOV 19/1200 UTC THRU NOV 23/0000 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-12Z NAM BLEND  
CONFIDENCE: AVERAGE  
   
..17Z UPDATE  
  
THE MOST SIGNIFICANT CHANGES FROM THE 12Z ECMWF/UKMET/CMC COMPARED  
TO THEIR PREVIOUS 00Z CYCLES WERE WITH THE CLOSED LOW CROSSING THE  
FOUR CORNERS INTO THE CENTRAL PLAINS THURSDAY/FRIDAY. THE 12Z  
ECMWF SLOWED DOWN GIVING GREATER SUPPORT TO A NON-12Z NAM BLEND.  
THE UKMET/CMC REMAINED FAIRLY CONSISTENT.  
  
ELSEWHERE, THERE WERE SOME CHANGES WITH THE CLOSED LOW SHIFTING  
DOWN OFF OF THE WEST COAST AS WELL, WITH THE 12Z ECMWF SHIFTING  
CLOSER TO THE COAST BUT IS QUICKER THAN MOST OF THE DETERMINISTIC  
GUIDANCE TO TRACK THE LOW SOUTHWARD. THE 12Z GFS/CMC ARE LIKELY  
CLOSEST TO THE LATEST/FAVORED ENSEMBLE MEANS WHILE THE 12Z NAM IS  
CLOSEST TO THE COAST. THE 12Z ECMWF AND 12Z UKMET ARE ACCEPTABLE  
WHEN INCLUDED AS PART OF A BLEND, EXCLUDING THE 12Z NAM.  
   
..PREVIOUS DISCUSSION FOLLOWS  
  
THE LARGE SCALE FLOW PATTERN ACROSS THE LOWER 48 WILL UNDERGO A  
TRANSITION FROM TROUGHING OVER THE EAST TO RIDGING ALONG THE EAST  
COAST BY FRIDAY. MEANWHILE ACROSS THE WEST COAST, A SERIES OF  
CLOSED LOWS WILL AFFECT PORTIONS OF THE WESTERN U.S.  
  
OVERALL, A BLEND OF THE 12Z GFS, 06Z GEFS AND 00Z UKMET WILL WORK  
FOR ALL SYSTEMS ACROSS THE CONUS. ONE OF THE BIGGER DIFFERENCES  
RELATES TO A CLOSED LOW LOCATED WEST OF THE BAJA PENINSULA AT 12Z,  
WHICH WILL WEAKEN AS IT TRACKS INTO THE SOUTHWESTERN U.S. ON  
WEDNESDAY. A RELATED SURFACE LOW WILL TRACK FROM THE CENTRAL  
PLAINS INTO THE GREAT LAKES REGION. AT THE SAME TIME, A NORTHERN  
STREAM, POSITIVELY TILTED MID-LEVEL TROUGH AXIS WILL APPROACH THE  
UPPER MISSISSIPPI VALLEY FROM THE WEST. TIMING DIFFERENCES WITH  
THE POSITIVELY TILTED TROUGH SHOW UP WITH THIS FEATURE AS IT  
TRACKS EAST TOWARD NEW ENGLAND MAINLY WITH THE SLOWER 12Z NAM.   
BETTER AGREEMENT EXISTS WITH THE GEFS/ECMWF ENSEMBLE MEANS AND THE  
12Z GFS, 00Z ECMWF AND 00Z UKMET.  
  
ANOTHER CLOSED LOW WHICH TRACKS ACROSS SOUTHERN CALIFORNIA  
WEDNESDAY EVENING IS EXPECTED TO TRACK EASTWARD TOWARD THE  
CENTRAL/SOUTHERN PLAINS WITH SOME WEAKENING BY FRIDAY AFTERNOON.  
ENSEMBLE SPAGHETTI PLOTS ARE SHOWING TRENDS TOWARD A MIDDLE GROUND  
SOLUTION, CURRENTLY BEST REPRESENTED BY THE 06Z GEFS, 12Z GFS AND  
00Z UKMET.  
  
LASTLY ACROSS THE WEST COAST, AN ELONGATED MID-LEVEL TROUGH AXIS  
WILL APPROACH THE PACIFIC NORTHWEST LATE THURSDAY, WITH SPLITTING  
INTO TWO PARTS. A STRONG MAJORITY OF AVAILABLE GUIDANCE KEEPS THE  
NORTHERN SPLIT INTO SOUTHERN CANADA WITH LITTLE TO NO IMPACTS ON  
THE U.S. THE SOUTHERN SPLIT WILL TRACK SOUTH OFF OF THE WEST COAST  
WITH ENSEMBLE MEANS FAVORING A MIDDLE GROUND BETWEEN THE EXTREMES  
OF THE DETERMINISTIC GUIDANCE. IN ADDITION TO THE MIDDLE GROUND  
ENSEMBLE MEANS, THE BEST REPRESENTATIVE DETERMINISTIC GUIDANCE IS  
THE THE 00Z UKMET.  
  
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
OTTO  
  
  
 
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