Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1223 AM EDT Sun Aug 19 2018

Valid Aug 19/0000 UTC thru Aug 22/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Synoptic Pattern across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 00Z GFS, 00Z NAM, 12Z CMC
Confidence: Slightly below average

Other than over the Southeast, near the westward extension of the
Bermuda ridge, model ensemble spread (500mb heights) is greater
than the past 30-day average over most of the CONUS. This reduces
forecast confidence a bit. Significant amplification of a ridge
into western Canada will have implications for amplification of
the pattern downstream. Models show differences in how they handle
the troughs. The 12Z ECMWF is much slower than the other
deterministic models with its surface low in the Midwest, as it is
with the trough axis aloft. It has reasonably good support from
its ensemble mean, but all other available models show a faster
progression. Because of this, the forecast was trended away from
the ECMWF for the WPC QPF. Out in the Western US, the 12Z UKMET is
out of phase with a secondary trough axis relative to the other
models. This also leads to greater differences downstream.
Therefore, the UKMET is not included in the preference either.
Otherwise, the GFS, NAM and CMC offer a decent consensus and
reasonable agreement on the overall synoptic pattern.


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

Lamers