619
FXUS10 KWNH 150645
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 AM EDT WED JUL 15 2020
VALID JUL 15/0000 UTC THRU JUL 18/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...LONGWAVE TROUGH AXIS MOVING THROUGH THE NORTH-CENTRAL U.S.
THROUGH WEDNESDAY WITH ACCOMPANYING SURFACE COLD FRONT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE
AS A LARGE CLOSED LOW AND ASSOCIATED LONGWAVE TROUGH AXIS TRACK
EASTWARD ACROSS SOUTHERN CANADA THROUGH THE REST OF THE WEEK, A
CORRESPONDING COLD FRONT WILL MOVE INTO THE GREAT LAKES AND GREAT
PLAINS. THE 00Z NAM DEVELOPS CONVECTION WITH A MORE ROBUST
RESPONSE ALOFT ACROSS THE CENTRAL PLAINS THAT TRANSLATES EASTWARD
TOWARD THE GREAT LAKES REGION BY THURSDAY MORNING. THE STRONGER
00Z NAM DOES NOT MATCH WELL WITH THE ENSEMBLE MEANS, SPAGHETTI
PLOTS AND THE PREFERRED 00Z GFS/ECMWF. THE 00Z UKMET IS ALSO A
LITTLE SLOWER BUT NOT AS STRONG AS THE 00Z NAM. THE 00Z CMC COULD
BE A SECONDARY OPTION TO THE 00Z GFS/ECMWF AS THE CANADIAN MODEL
IS THE NEXT MOST SIMILAR PIECE OF GUIDANCE TO THE PREFERENCE.
HOWEVER, BOTH THE 00Z UKMET/CMC ARE STRONGER WITH THE MID-LEVEL
RIDGE IN PLACE OVER THE CENTRAL TO SOUTHEASTERN U.S. WHEN COMPARED
TO THE REMAINING GUIDANCE.
..CUT OFF LOW WEST OF CALIFORNIA BY THURSDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS FROM 00Z ARE IN GOOD AGREEMENT, SHOWING THE FORMATION
OF A CLOSED LOW JUST WEST OF CA TODAY, AND ITS SLOW WESTWARD
TRANSLATION THROUGH THE END OF THE WEEK INTO THE OPEN PACIFIC.
ONLY MINOR TIMING/PLACEMENT DIFFERENCES WERE NOTED, BUT THEY ARE
SMALL ENOUGH THAT A GENERAL MODEL BLEND CAN BE USED FOR THIS
SYSTEM.
...PROGRESSIVE TROUGH CROSSING THE PACIFIC NORTHWEST ON THURSDAY,
SOUTH-CENTRAL CANADA BY SATURDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z NAM BLEND, LED BY 00Z GFS/ECMWF
CONFIDENCE: AVERAGE
THE 00Z NAM WAS NOTED TO BE SIGNIFICANTLY SLOWER WITH THE EASTWARD
TRANSLATION OF A MID-LEVEL TROUGH AXIS THROUGH THE NORTHWEST INTO
THE NORTH-CENTRAL U.S. FRIDAY INTO SATURDAY. THE DIFFERENCES AT
THE SURFACE ACROSS THE U.S. ARE RELATIVELY MINOR, BUT GIVEN THE
DIFFERENCES IN THE NAM ALOFT, IT IS NOT RECOMMENDED TO BE USED FOR
THIS PORTION OF THE COUNTRY. THE 00Z UKMET/CMC SHOW BETTER TIMING
ALOFT BUT HAVE DIFFERENCES WHEN COMPARED TO THE ENSEMBLE MEANS AND
00Z GFS/ECMWF REGARDING THEIR GREATER AMPLIFICATION OF THE 850-700
MB TROUGH REFLECTION ACROSS SOUTHERN MANITOBA/SOUTHWEST ONTARIO
FRIDAY NIGHT.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
OTTO
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