Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
246 AM EDT Wed Apr 03 2019

Valid Apr 03/0000 UTC thru Apr 06/1200 UTC

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

00Z Model Evaluation with Preferences and Confidence
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...Powerful surface low lifting up off New England...
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Preference: General model blend
Confidence: Above average

The models are in reasonably good agreement with the details of
the powerful surface low offshore of the Mid-Atlantic states which
will quickly lift northeast up offshore New England early
Wednesday and then cross Nova Scotia and adjacent areas of
southeast Canada Wednesday afternoon/evening. The 00Z NAM/GFS
solutions tend to be just a tad faster than the non-NCEP models as
per the 00Z UKMET/CMC and ECMWF, but at this point a general model
blend should suffice to resolve these modest timing differences.


...Shortwave reaching the Four Corners on Wed...
...Cyclogenesis over the Southern Plains by Thurs...
...Energy shearing toward the OH/TN Valleys by Fri...
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Preference: Blend of the 00Z NAM/GFS and 12Z ECENS mean
Confidence: Average

The models handle this feature similarly through early Thursday
with at least some modest timing and depth differences by late
Thursday as the 00Z ECMWF begins to slow its shortwave evolution
down just a bit, and the 00Z NAM begins to become a tad stronger
than the remaining guidance. The 00Z GFS begins to outpace the
model consensus by just a tad on Friday as the energy reaches the
OH/TN Valleys. At the surface, the guidance shows good agreement
with the low center over the southern Plains, but as the system
dampens out toward the OH/TN Valleys, there is some spread with
the details of weak low pressure. The 00Z NAM/GFS/ECMWF solutions
all tend to hang onto somewhat of a more defined low that at least
lifts up across OH Valley and toward the lower Great Lakes region
and this is supported by the latest GEFS mean and ECENS mean.
Although, the ECMWF is slower with the surface wave evolution
across this region. The 00Z CMC/UKMET solutions are more
diffuse/weaker. The best overall clustering tends to reside with
the 00Z NAM/GFS and 12Z ECENS mean, and so a blend of these
solutions will be preferred.


...Shortwave troughs approaching the West Coast...
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Preference: Blend of the 00Z GEFS mean/12Z ECENS mean
Confidence: Average

Models show agreement that a shortwave should reach the West Coast
by late Thursday, with another following in rapid succession on
Fri. Solutions differ a bit on the separation between these
features and on the structure (closed upper low or negatively
tilted but more progressive trough). What seems clearer is that as
the leading wave encounters broad anticyclonic upper-level flow
across the Great Basin/Rockies, energy should separate out with a
southern stream component crossing reaching the Four Corners
region by Friday. The 00Z ECMWF/UKMET solutions become a bit
slower than the 00Z NAM/GFS/CMC with the southern stream extension
by Friday. The northern stream based energy coming across the
Pacific Northwest tends to be a bit better agreed upon among the
models. Although, the 00Z GFS is likely to strong with the
shortwave and attendant surface low approaching the Pacific
Northwest on Friday. The 00Z GEFS mean and 12Z ECENS mean offer a
nice compromise solution overall, and a blend of these will be
preferred to resolve some of the smaller scale detail differences
noted with shortwave timing and depth.


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

Orrison