Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
327 AM EDT Thu Apr 25 2019

Valid Apr 25/0000 UTC thru Apr 28/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend, weighted to ECMWF
Confidence: Average

07z update: No significant changes noted with the rest of the 00z
guidance now available. Most notable model differences remain on
Day 3 across the northern stream energy across the northern Plains
and Upper Midwest, where is there is a north/south shift in the
track of the low pressure and its associated QPF fields. For now,
will still lean on a general model blend, noting the uncertainty
and thermal differences that will have sensible weather impacts.

---previous discussion---
The shortwave energy currently moving across the southern Plains
will work toward the mid-Atlantic and phase with northern stream
energy by Friday night, becoming negatively tilted over the
Northeast US and New England. Models have come into better
agreement with the large scale mass fields as the system evolves
over the next couple days. As the system phases with the northern
stream energy, how deep/fast it pushes off the coast remains
uncertain, with the deterministic models showing varying degrees
of solutions. The GFS is more amplified as well as faster compared
to the NAM. The CMC is flatter compared to the rest of the
guidance. Toward the end of the period (Saturday), the ECMWF
closes off and thus slows down considerably while the NAM quickly
takes the shortwave off the New England coast. The preference is
toward the ECMWF solution given the support from the ECENS and
other ensemble members, but for the first 48-60 hours, a general
model blend can be applied.

Fast northern stream energy develops in the wake of the east coast
system as a pair of shortwaves move onshore in the Pacific
Northwest and track through the northern Rockies and Plains. There
are some subtle timing differences, but for the most part,
strength/amplification is similar through Saturday with the
initial feature tracking through the Plains/Upper Midwest. Looking
at the QPF fields, there is some north/south placement issues but
the differences are relatively minor on Day 3. For the secondary
feature coming into the Pacific Northwest and Northern Rockies on
Saturday and Saturday night, the NAM is considerably more
amplified than the ECMWF/CMC. Overall though, a general model
blend can be applied for these features through Day 3.


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

Taylor