Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1139 AM EST Fri Dec 06 2019
Valid Dec 06/1200 UTC thru Dec 10/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation with Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: Non-NAM Blend
Confidence: Average
The synoptic pattern over the CONUS will undergo considerable
amplification over the next few days with a trough building into
the Central U.S. and a ridge building along the Pacific coast.
Models are in good agreement with some minor timing or amplitude
variations. Through the first three days of the forecast, global
models generally place QPF in the same areas and mass field spread
in the ensembles is somewhat limited in the same time frame.
Therefore, a general model blend is the preference, with slightly
less weight placed on the 12Z GFS due to a tendency toward lower
heights in the southern stream and slightly faster progression of
a shortwave trough in the Southwest on Monday (contrary to
consensus and its ensemble mean).
The one exception will be the 12Z NAM, which is not included in
the preference. The NAM shows a much stronger shortwave digging
south along the West Coast and eventually arriving in the
Southwest, which is only marginally supported by the 00Z UKMET.
Additionally, despite a similar evolution of the trough and
surface low track over the eastern half of the country, it
concentrates much of its heavier QPF along the Atlantic coast on
Sunday Night and Monday, with much lower QPF further inland in the
Ohio Valley and Great Lakes. This is in contrast to all of the
global models, and the preference is to lean toward the global
models which have much stronger ensemble support.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Lamers