Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1227 AM EDT Wed Oct 31 2018

Valid Oct 31/0000 UTC thru Nov 03/1200 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
Confidence: Average

Over the next few days, deterministic models are in relatively
good agreement on the synoptic pattern and QPF despite a moderate
amount of model spread in the mass fields beyond 01/12Z (Thursday
and Friday). For their height fields, the deterministic models are
well within the envelope of ensemble spread and an average of the
deterministic models yields a forecast reasonably similar to the
GEFS and ECMWF ensemble means. Therefore, the preference is to
lean toward a general model blend.

For the specifics of WPC QPF, particularly as it relates to 6hr
QPF in the Eastern US, the official forecast deviates slightly
from the general model blend to account for expected progression
of convection based on model forecasts of available moisture,
instability, and wind fields. This leads to slightly higher QPF
maxima than a simple blend would yield, and greater weight placed
on certain deterministic models in different regions and time
frames. Overall, though, WPC QPF is fairly close to the general
model blend.

In the Pacific Northwest, the NAM was used to highlight some
increased QPF in certain upslope regions most favorably positioned
relative to the low-mid level mean wind vectors and highest PW
plume. Some of the global models may have a slight dry bias with
their forecast QPF.


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

Lamers