Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
251 PM EDT Mon May 13 2019

Valid May 13/1200 UTC thru May 17/0000 UTC

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

12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence
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...Overall Pattern across the CONUS...
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Preference: 12Z GFS/12Z ECMWF blend
Confidence: Average

...19Z update...

No significant differences were noted in the East with the 12Z
ECMWF/UKMET/CMC relative to their previous 00Z cycles. Out West
though, there has been some convergence with the 12Z
ECMWF/UKMET/CMC converged closer to the GFS solution with the
placement/strength of the low and mid-level low such that better
agreement is now in place. A non-12Z NAM blend weighted toward the
12Z GFS/ECMWF is considered best across the West Coast at this
time.

...previous discussion follows...

Amplified flow will be in place across the lower 48 through
Thursday with mid-upper level troughing out West, ridging across
the central CONUS and troughing in the East. The biggest
differences regarding mass fields are with a shortwave forecast to
reach the northern Mid-Atlantic region early Thursday morning. The
ensemble means show good agreement toward the timing of the 12Z
NAM/12Z GFS and 00Z ECMWF with the 00Z UKMET/CMC faster. Despite
some differences among the NAM/GFS/ECMWF, a blend of these three
models appears best across the East for Wednesday into Thursday.
Across the West, a potent upper trough is expected to reach
California Wednesday into Thursday. The guidance and ensembles
have trended stronger and farther south compared to yesterday. The
latest ensemble means support a solution close to the 12Z GFS with
the 00Z ECMWF a close second, though the ECMWF is stronger in the
low levels and displaced slightly to the west. The 00Z UKMET shows
similar to the 00Z ECMWF across the West. The preference will be
for a 12Z GFS/00Z ECMWF blend given some tempering of the ECMWF
strength and southward displacement is favored. Elsewhere across
the CONUS, differences are driven largely by differences in
convective evolution more so than mass field differences.

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

Otto