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Model Diagnostics Discussion
 
(Latest Discussion - Issued 0645Z Jul 05, 2020)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
244 AM EDT Sun Jul 5 2020

Valid Jul 5/0000 UTC thru Jul 8/1200 UTC

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

00Z Initial Model Evaluation Including Preferences and Forecast
Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

6Z Update:  The 00Z UKMET remains strong with the central U.S.
upper ridge compared to the other guidance, but slightly weaker
compared to its 12Z run.  The CMC trended much more in line with
the consensus regarding the Pacific Northwest trough, albeit
slightly faster.  The ECMWF trended slightly more progressive by
the end of the forecast period across the northern Rockies and
northern Plains, but is similar across most other places. 
Otherwise no major changes warranted to the forecast preferences.

Trough building over the Northeast U.S. this weekend
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Slightly above average

The next shortwave trough in northwest flow is forecast to amplify
some over northern New England by late Sunday with an upper low
becoming likely by Monday across Nova Scotia, followed by low
amplitude upper ridging arriving from Quebec early in the week. 
Models in the low-mid levels are in good agreement through Monday
evening, after which the NAM becomes a bit more amplified.  At the
jet stream level, the 18Z and 00Z GFS are a little more
progressive with the trough axis, but still close enough to be
part of the model blend. A general model blend should work well
for this region.


Trough/weakness over the Gulf Coast region
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-UKMET blend
Confidence: Average

A rather broad weakness in the larger scale upper ridge across the
Deep South and Southeast U.S. should remain nearly anchored in
place through the beginning of the week, with a hint of a weak
upper low trying to develop by Monday across the central Gulf
Coast region.  Remnant MCVs and convectively enhanced shortwaves
are expected to be present within this broad trough, along with a
weak surface frontal boundary.  The main model difference noted
here is a weaker and farther west solution with the 12Z UKMET,
owing to a much stronger ridge across the central U.S. that falls
outside the ensemble spread by Tuesday.


Trough with multiple shortwaves across the Pacific Northwest and
Canada
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend through 00Z Tuesday, then
NAM/GFS/ECMWF blend
Confidence: Above average

General troughing is expected to continue across the Pacific
Northwest and northern Rockies through the forecast period with a
few separate shortwave troughs moving through the flow.  One
currently is lifting across the northern Rockies and then track
across south-southern Canada.  Followed by brief interim
low-amplitude ridging, another shortwave trough reaches
Oregon/Washington Monday afternoon.  A third perturbation enters
the offshore waters of the Pacific Northwest by Wednesday morning
with the core of the upper trough remaining anchored over western
Canada.  The UKMET becomes weaker with the first shortwave by
Sunday night across Saskatchewan and Manitoba, whilst becoming a
little more amplified with the second shortwave.  The CMC is noted
as a much weaker solution across the Pacific Northwest by Monday
night across the Pacific Northwest, and slower with the arrival of
the third offshore system. 


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

Hamrick