Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
339 AM EDT Sun Oct 20 2019

Valid Oct 20/0000 UTC thru Oct 23/1200 UTC

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

00Z Model Evaluation with Preferences and Confidence
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Northern stream shortwave and surface cyclogenesis Plains/Upper
Midwest
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Preference: General model blend; weighted toward ECMWF/GFS/UKMET
Confidence: Average

07Z Update: No significant changes noted with the rest of the 00Z
guidance now available - the 00Z CMC did trend a bit better toward
the rest of the model consensus such that some of it can be
incorporated. The 00Z ECMWF was not as deep with its surface low
over MN/WI compared to its 12Z run and is now more in line with
the rest of the 00Z guidance. Overall, track and minimum SLP is
fairly clustered such that a general blend can be incorporated.

---previous discussion---
Shortwave energy currently moving through the northern Rockies
will eject out into the central/northern Plains later today. All
of the available deterministic and ensemble guidance closes off
the mid-level low at 500 mb by 18Z, with better clustering in the
position/axis of this trough now compared to the previous model
cycles. As the low moves into portions of the Dakotas and
Nebraska, the CMC quickly falls out of favor as it is too deep/amp
flied as well as slow and to the south of the model consensus. Its
solution should be discarded. By 48 hours /22.00Z/ the mid/upper
level low reaches the Upper Mississippi River Valley. At the
surface, cyclogenesis will occur along the NE/SD border with a
secondary low expected to form across north Texas. The northern
low will be dominant at first but then as the southern low lifts
northeast, it will become absorbed with the stronger/northern low
in the vicinity of MN/IA/WI. The ECMWF/NAM depict the low center
over western WI while the GFS/UKMET keep the initial low to the
west dominant. After 48 hours all the models depict one low center
across northern Wisconsin as the while system becomes
occluded/stacked. For model preference, through 22.00Z the CMC
should not be included or considered. Thereafter, a blend of the
ECMWF/GFS/UKMET is preferred as confidence trends toward average.

Third fast moving shortwave entering Northern US Rockies/MT High
Plains late Tuesday
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Preference: General model blend
Confidence: Average to slightly below average

The 3rd more significant shortwave, will over-top the broad
longwave ridge peaking around Vancouver Island and slip into the
Northern US Rockies and MT High Plains. Model guidance is in
decent agreement with very little spread seen between the 00Z
GFS/NAM and 12Z ECMWF/UKMET/CMC at 500 mb. At the surface, the NAM
surface low depiction is fast, particularly on Day 3 but is with
the model spread envelope, so it can still be incorporated.
Overall, will favor a general model blend given the relatively
good agreement.


Post-tropical Storm Nestor
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Preference: 00Z GFS, 12Z ECMWF/UKMET
Confidence: Average to slightly above average

Post-tropical cyclone Nestor has lost its near center convection
with the latest center inland across Georgia. The most recent
model guidance is in reasonable agreement that the center will
move toward eastern North Carolina later today and then offshore
the Mid-Atlantic coast this evening. The system then will slow and
gradually dissipate and/or become absorbed within troughing over
the eastern CONUS early to mid next week. After 30-36 hours, model
spread does increase regarding the track - with the NAM being left
of the model consensus and CMC to the right. The 00Z GFS along
with the 12Z ECMWF/UKMET is a reasonable consensus at this time.


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

Taylor