Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
247 PM EDT Wed Aug 14 2019

Valid Aug 14/1200 UTC thru Aug 18/0000 UTC

...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...

12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend outside of the north-central U.S.
            12Z NAM/ECMWF/CMC blend in north-central U.S.
Confidence: Average

...19Z update...

Trends in the 12Z ECMWF/CMC were toward the better ensemble
clustering, more of a middle ground between the faster 12Z GFS and
slower 00Z ECMWF concerning the upper trough in the north-central
U.S. late Friday. Elsewhere across the U.S., changes were minor
with a general model blend continuing to be recommended.

...previous discussion follows...

The upper level pattern starts off with strong ridging across the
Southwest and northwesterly flow to its north, leading to broad
troughing across the eastern half of the nation. The ridge becomes
suppressed on Friday as upper level troughing begins to impinge
upon the Northwest, leading to broad quasi-zonal flow from the
Pacific Northwest to the Northeast.

Anomalous moisture will remain in place ahead of a slow moving
front which will extend from the Mid-Atlantic region to the Gulf
Coast, while impulses in northwest flow aloft keep the central
Plains to the Midwest active with organized convection. There is
broad agreement with the synoptic scale features across these two
areas with a general model blend recommended. Elsewhere, a general
model blend across the CONUS appears okay as well.

The one area where the models show differences is with a cold
front, related to upper level troughing in Saskatchewan and
Alberta Friday night into Saturday. Here, the 12Z GFS shows as a
near outlier with a more progressive trough related to vorticity
wrapping around the west side of a closed low in northern
Saskatchewan. The 00Z ECMWF is on the other extreme, but within
the spread, regarding the vorticity max dropping south to the west
of the closed low in northern Saskatchewan. A 12Z NAM/00Z ECMWF
blend represents closest to the ensemble means. 

Model trends at www.wpc.noaa.gov/html/model2.html
500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml

Otto