664
FXUS10 KWNH 181849
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 PM EDT SAT JUL 18 2020
VALID JUL 18/1200 UTC THRU JUL 22/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..NORTHERN TIER OF THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE NORTHERN TIER OF THE CONUS WILL REMAIN ACTIVE WITH FAST FLOW
ATOP AN EXPANSIVE MID-LEVEL RIDGE COVERING MUCH OF THE CENTRAL AND
SOUTHERN U.S. A PAIR OF SHORTWAVE TROUGHS THOUGH WILL BE ADVANCING
ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST GOING THROUGH EARLY
NEXT WEEK, WITH A SHORTWAVE TROUGH ALSO EXPECTED TO BE APPROACHING
THE PACIFIC NORTHWEST BY LATE TUESDAY.
THE 12Z CMC APPEARS A JUST A TAD TOO SLOW WITH THE FIRST SHORTWAVE
CROSSING THE NORTHERN PLAINS AND UPPER MIDWEST ON SUNDAY. BY
TUESDAY AS THE NEXT SHORTWAVE ARRIVES ACROSS THIS REGION, THE 12Z
UKMET APPEARS TO BE A BIT TOO WEAK, WITH THE 12Z CMC LOOKING NOW
TO BE A LITTLE TOO FAST. BY LATE TUESDAY WITH THE ENERGY
APPROACHING THE PACIFIC NORTHWEST, THE 12Z NAM MAY BE A TAD TOO
STRONG AND SLOW WITH ITS ENERGY GIVEN THE GOOD GLOBAL MODEL
CLUSTERING SEEN OTHERWISE. OVERALL, THE PREFERENCE IS TOWARD A
BLEND OF THE 12Z GFS AND 12Z ECMWF ACROSS THE NORTHERN TIER OF THE
CONUS GIVEN THEIR BETTER CLUSTERING WITH ALL THREE SHORTWAVE
TROUGHS MENTIONED.
..CALIFORNIA/SOUTHWEST U.S
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM/GFS/ECMWF
CONFIDENCE: AVERAGE
THE MODELS ADVERTISE A BROAD MID-LEVEL TROUGH ALONG AND JUST
OFFSHORE OF NORTHERN/CENTRAL CA BY MONDAY AND TUESDAY, WITH A
SEPARATE SMALLER SCALE SHORTWAVE TROUGH DEVELOPING OVER AREAS OF
THE SOUTHWEST INVOLVING SOUTHERN NV, SOUTHWEST CA, WESTERN UT AND
NORTHWEST AZ BY LATE TUESDAY. THE 12Z CMC AND 12Z UKMET BOTH ARE
ON THE WEAKER SIDE OF THE GLOBAL MODEL SUITE WITH BOTH SYSTEMS.
THE 12Z NAM, 12Z GFS AND 12Z ECMWF ARE RELATIVELY BETTER CLUSTERED
WITH PLACEMENT AND POSITIONING OF THESE TROUGHS, AND HAVE BETTER
ENSEMBLE SUPPORT FROM THE GEFS/ECENS MEANS. THUS A BLEND OF THE
NAM, GFS AND ECMWF WILL BE PREFERRED.
..MID-LEVEL EASTERLY WAVES IMPACTING THE SOUTHERN CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: AVERAGE
A SERIES OF MID-LEVEL TROUGHS/EASTERLY WAVES WITH AT LEAST A
MODEST SURFACE REFLECTION WILL IMPACT THE SOUTHERN TIER OF THE
CONUS OVER THE NEXT FEW DAYS WITH AN EMPHASIS ON THE RIO GRANDE
VALLEY, GULF COAST, AND THE FL PENINSULA. THE 12Z NAM IS GENERALLY
A TAD TOO STRONG IT APPEARS WITH THIS WAVE ACTIVITY AS THE GLOBAL
MODELS AND THE ENSEMBLE MEANS ARE ALL GENERALLY FLATTER WITH THEIR
WESTWARD PROPAGATION THROUGH THE PERIOD. A NON-NAM BLEND WILL BE
PREFERRED WITH THE WAVE ACTIVITY AS A RESULT ACROSS THE SOUTHERN
TIER OF THE CONUS.
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.
ORRISON
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