Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1244 AM EDT Sun Mar 17 2019
Valid Mar 17/0000 UTC thru Mar 20/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
00Z Model Evaluation Including Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of 12Z ECMWF and 00Z GFS
Confidence: Slightly Above Average
The primary synoptic pattern over the next few days will feature a
ridge amplifying considerably over the West, with a gradually
eroding trough in the Great Lakes and Northeast. The position of
these features, as well as expansive surface high pressure over
most of the country should keep precipitation generally
concentrated over the Gulf of Mexico and Florida, and off the West
Coast for much of the forecast period.
There will be several exceptions to that, and those are the areas
of greatest model disagreement at the moment. First, models are in
excellent agreement that a shortwave will dig sharply south from
Canada into the Plains early next week as the western ridge
amplifies. However, they do show notable differences in timing and
amplitude. In general, the 12Z ECMWF and 00Z GFS offer a
reasonable consensus. Other models do not extend the digging
trough as far to the west, and the 00Z NAM and 12Z CMC and UKMET
are less amplified than even the ensemble means. They also show a
faster progression. The preference is to lean closest to the
deterministic models that resemble the ensemble means.
Second, the timing of the arrival of a trough into California has
reasonably large spread by Wednesday morning. The 00Z GFS and NAM
are a full degree or two of longitude faster than the remaining
deterministic models, and even faster than the 18Z GEFS Mean. It
is a typical bias for the ECMWF to be on the slow end and the GFS
to be on the fast end, so a compromise between these extremes is
preferred, with perhaps a slight lean toward the ECMWF given that
the GFS is faster than its ensemble mean as well.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Lamers