Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1233 AM EDT Thu Jun 13 2019

Valid Jun 13/0000 UTC thru Jun 16/1200 UTC

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

00Z Preliminary Model Evaluation...with Confidence and Preferences
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...Great Lakes/Ohio Valley/East Coast...
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Preference: 12Z.12 ECMWF/ECENS/UKMET
Confidence: Average

Uncertainty abounds even early on day 2 /Friday/ due to spatial
and temporal discrepancies in the interaction of energy shedding
from a vortex over eastern Canada and a trough digging through the
Great Lakes/Northeast CONUS. There appears to be two distinct
pieces of energy which will rotate around the CONUS trough, with
the guidance differing on which will be the primary, leading to
timing differences of the eastern translation of the trough. The
NAM/CMC suggest the lagging shortwave will dominate which suggests
a slower progression of the trough and associated surface front,
while the GFS/ECMWF/UKMET favor the leading shortwave and a faster
solution. Although the ridge downstream is amplified, it has a
very short wavelength and expect the faster solutions will verify,
especially as most guidance has been too slow with ongoing
evolution early this morning. Although the GFS is usable D1-D2, by
D3 renewed troughing digs in from central Canada, and the GFS is
much stronger /lower heights/ across the Plains and Great Lakes
than the global consensus. As this is the new FV3/GFS, there is
little to discern as far as trends, so as it is a strong outlier
would be hesitant to include much of it by day 3, and favor the
more consistent and clustered UKMET/ECMWF which also match with
the heaviest QPF across the Ohio Valley by the end of the period.


...Western and Southern U.S...
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Preference: Non-ECMWF Day 1, Non-NAM Days 2-3
Confidence: Above average

The flow across the West and South becomes generally zonal as the
eastern trough lifts away Friday before developing broad cyclonic
flow into the weekend. During day 1, the most significant
variation involves a shortwave moving across the Southwest into
Texas. While nearly all the guidance has this feature, the ECMWF
is very quick to dissipate into a downstream shortwave ridge, and
produces little to no QPF across the Panhandle of Texas. This is
an outlier and is not included in the preferred blend. Thereafter,
many of the features across the west and south are related to
mesoscale impulses moving through the flow, with a more
substantial longwave trough developing the latter half of this
discussion period. Timing and Spatial extent of these small scale
features are difficult to discern beyond near-term time scales, so
other than the NAM which is notably stronger with several impulses
translating eastward, a general model blend should suffice.


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

Weiss