Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1259 PM EDT Wed Sep 05 2018

Valid Sep 05/1200 UTC thru Sep 09/0000 UTC

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

12Z model evaluation...with latest preferences and confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: Blend of 00Z ECMWF, 00Z UKMET, 12Z GFS
Confidence: Slightly above average
 
Model mass field agreement is generally quite good across the
CONUS, with the deterministic models generally contained well
within the envelope of ensemble spread. Therefore, a general blend
is preferred overall. The greatest QPF differences were over the
Midwest as Gordon interacts with an approaching trough. In
general, the NAM and CMC kick the low out to the northeast faster
than the other models, and represented greater differences with
their QPF relative to the ensemble means and other global models.
Thus, the preference was weighted more substantially toward the
ECMWF, UKMET and GFS, particularly in the central CONUS.


...Tropical Depression Gordon...
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Preference: Please consult the latest NHC forecast
 
The model QPF differences are most notable when Gordon (or the
remnant low) begins to interact with a trough over the central
CONUS. However, there are even some notable QPF differences in the
early part of the forecast. The 00Z ECMWF, for example, generates
a significant QPF maximum over Arkansas, much more than other
deterministic models. The ECMWF was underestimating the extent of
the band of convection to the east of Gordon's center, and
concentrating the QPF closer to the surface center. Therefore, the
ECMWF QPF may be less reliable in the near-term over the southern
CONUS. More hi-res model guidance was incorporated in this region,
with a greater weight to the ECMWF, GFS, and UKMET beyond 48 hours
as the trough interaction begins.


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

Lamers