Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
305 AM EDT Tue Oct 22 2019

Valid Oct 22/0000 UTC thru Oct 25/1200 UTC

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

00Z Model Evaluation with Preferences and Confidence
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Central U.S. cyclone; secondary low from Carolinas to New England
Today-Wed.
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Preference: General model blend
Confidence: Above average

Occluded low near MSP will continue to lift north/northeast over
the next 48 hours into western Ontario and gradually become
stacked with the upper level low. Its strength will more or less
maintain itself the next 2 days then some gradual weakening is
expected. A secondary low pressure will form across the southern
Appalachians and then lift along the eastern U.S. coastline.
Overall, with both of these features there is very good agreement
with above average forecast confidence in the placement and
strength such that a general model blend is sufficient.


Stronger shortwave dropping through Rockies into the southern
Plains early to mid week
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Preference: ECENS mean (with some CMC/UKMET weight)
Confidence: Below average

07Z update: With the rest of the 00Z guidance now available, there
was not much, if any, trend toward better agreement on the
evolution of the mid/upper level shortwave energy over the
southwest US and southern Plains late in the week. The 00Z
ECMWF/CMC in fact trended deeper, digging the low well into New
Mexico. The UKMET is closed off as well, but not as far (TX
Panhandle at 25.12Z). This is in stark contrast to the NCEP
guidance (GFS/NAM) which is flatter and more progressive. Given
the higher than usual spread at 3 days, the WPC preference is
still for a solution similar to the ECENS mean, which digs the low
well into the southwest US, but isn't as agressive as the
deterministic EC. Forecast confidence is below average.

---previous discussion---
Shortwave energy dropping southward through the Canadian Rockies
and building heights over the eastern Pacific will lead to an
amplified pattern by later in the week. Strengthening southern
stream energy will develop across the southwest into west Texas.
The ECMWF remains the most amplified, closing off the mid/upper
level feature though there is some support with the CMC as well.
Looking at the last several model runs, the GFS has been slowly
trending toward the ECMWF solution, though not as aggressive while
subsequent runs of the ECMWF have been fairly consistent.

The WPC preference remains for a heavy weight toward the non-NCEP
guidance but not as amplified as the deterministic ECMWF suggests,
with most of the weight toward the ECENS mean which is a good
compromise at this point until forecast confidence increases and
model spread lowers.


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

Taylor