879
FXUS10 KWNH 080657
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT SAT AUG 8 2020
VALID AUG 8/0000 UTC THRU AUG 11/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
OVERALL WEATHER PATTERN ACROSS THE CONTINENTAL U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 12Z SUNDAY, THEN
ECMWF/GFS/CMC
CONFIDENCE: AVERAGE
7Z UPDATE: THE 00Z NAM IS SLOWER AND CONSIDERABLY STRONGER WITH
THE SHORTWAVE CROSSING THE NORTHERN PLAINS AND UPPER MIDWEST ON
MONDAY COMPARED TO ALL OF THE OTHER 00Z GUIDANCE. THE ECMWF
TRENDED SLIGHTLY STRONGER WITH THE UPPER RIDGE ACROSS THE MIDWEST
AND THE OHIO VALLEY AND IN LINE WITH THE UKMET. OTHERWISE, NO
MAJOR CHANGES NOTED WITH THE ARRIVAL OF THE FULL 00Z MODEL SUITE.
----------
THE OVERALL WEATHER PATTERN ACROSS THE CONTINENTAL U.S. WILL BE
QUASI-ZONAL ACROSS THE NORTHERN TIER STATES ON SATURDAY WITH A
BUILDING UPPER RIDGE CENTERED OVER THE SOUTHERN PLAINS REGION. A
WEAK TROUGH AXIS OVER THE MID-ATLANTIC REGION AND THE NORTHEAST
U.S. WILL CONTINUE TO SLOWLY EMERGE OFFSHORE FOLLOWED BY LOW
AMPLITUDE RIDGING ALOFT. THERE WILL ALSO BE A BROAD, POSITIVELY
TILTED TROUGH AXIS STRETCHED ACROSS THE INTERMOUNTAIN WEST AND
EXTENDING ACROSS CALIFORNIA. THE MAIN WEATHER FEATURE WILL BE AN
EVOLVING CLOSED LOW OVER SOUTH-CENTRAL CANADA WITH MULTIPLE
SHORTWAVE PERTURBATIONS ROTATING AROUND ITS SOUTHERN PERIPHERY,
AND THESE SHORTWAVES WILL SUSTAIN COLD FRONTAL PASSAGES ACROSS THE
NORTH-CENTRAL U.S. THROUGH MONDAY.
THERE IS ENOUGH DETERMINISTIC MODEL AGREEMENT THROUGH 12Z SUNDAY
TO MERIT THE USE OF A GENERAL MODEL COMPROMISE. BEYOND THAT, THE
00Z NAM BECOMES A BIT MORE AMPLIFIED WITH THE UPPER LOW ACROSS
SASKATCHEWAN AND MANITOBA, AND SLOWER WITH THE SHORTWAVE CROSSING
THE NORTHERN PLAINS BY MONDAY. THE GFS IS MORE POTENT WITH THE
LEADING SHORTWAVE ACROSS THE UPPER MIDWEST BY MONDAY MORNING. THE
12Z UKMET IS A LITTLE STRONGER WITH THE UPPER LEVEL RIDGE ACROSS
THE OHIO VALLEY BY THE END OF THE FORECAST PERIOD. TAKING THESE
FACTORS INTO ACCOUNT, USING A 12Z ECMWF/GFS/CMC BLEND AS A MASS
FIELD STARTING POINT SHOULD WORK WELL.
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.
HAMRICK
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