Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Wed Jul 03 2019

Valid Jul 03/1200 UTC thru Jul 07/0000 UTC

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

12Z Final Model Evaluation...with Confidence and Preferences
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...Overall Pattern Across the CONUS...
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Preference: Non-CMC Days 1 and 2, GFS/NAM/ECMWF Day 3
Confidence: Slightly above average


19Z Update: Biggest change with the 12Z Non-NCEP suite was with
respect to the UKMET. While the previous iterations of the UKMET
were too strong with the eastern ridge and much too wet across the
Northern Plains, it has considerably scaled back both of these
discrepancies. While it is still a little too warm with its 500
heights across the east, the spread has closed, and the rainfall
signature is much more in line with the rest of the global suite.
The UKMET is now usable through day 2, albeit with limited weight,
before its spread increases and should remain excluded on day 3.
Otherwise, the blend remains unchanged as any differences are
related to small scale impulses which struggle to be resolved on
synoptic temporal and spatial scales.

Previous Discussion:
Models are in generally very good agreement in the overall
synoptic evolution over the next three days. A closed low over
Saskatchewan/Alberta will fill and lift northeast, while a
secondary piece of energy drops into the Pacific Northwest and
closes off, reinforcing the positively tilted trough across the
west. Downstream of this feature, an expansive mid-level ridge
will dominate the eastern 2/3 of the CONUS.

While the guidance is in good agreement with this setup, the UKMET
is much too warm with its 500mb heights within the ridge,
averaging 4-6dm higher than the global mean. With its heights
across Canada roughly the same, it is funneling more moisture on
stronger geostrophic flow into the Plains, and creating QPF that
is significantly higher than any other member, and should be
excluded from the blend. The CMC is very quick with its series of
impulses lifting through the trough and into the Plains,
especially with a strong feature on the 5th. While the overall
placement is within the ensemble envelope, it is temporally
displaced east by quite a bit, and should be used with caution as
it is these mesoscale features that will drive most of the QPF
across the country. The 00Z ECMWF and 12Z GFS/NAM are in good
agreement despite intensity differences of shortwaves moving
through the flow, and are weighted heavily in the blend. Do note
that the GFS is on the low-end of QPF forecasts across the Plains
by day 3, so a GEFS mean is also incorporated to trend towards
some of the higher QPF potential late in the period.

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

Weiss