Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
319 AM EDT Tue Jun 04 2019

Valid Jun 04/0000 UTC thru Jun 07/1200 UTC

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

00Z Model Evaluation with Confidence and Preference
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...Overall Pattern Across the CONUS...
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Preference: Blend of 00Z GFS, 00Z ECMWF, 00Z UKMET
Confidence: Slightly above average

---07Z UPDATE---
The 00Z UKMET has slowed its progression of the low in the western
Gulf of Mexico and associated trough to be better in line with the
ECMWF and GFS. Therefore, a blend of the GFS, ECMWF and UKMET is
still preferred.

---PREVIOUS DISCUSSION---
Models continue to be in very good agreement with the northern
stream; this will begin with zonal flow near the Canadian border
at the beginning of the forecast period, and transition to a
pattern with troughs on either coast and a gradual amplification.
All of the deterministic model mid-upper level height forecasts
are contained well within the full envelope of ensemble spread.
The one exception is the 00Z NAM, which seems to progress the
amplifying trough in the Northwest faster than the other
deterministic models. Therefore, the NAM is not favored in the
model preference there.

Further to the south, models have gradually converged on a similar
forecast with how the area of low pressure in the western Gulf of
Mexico will interact with a mid-upper level low ejecting east into
the southern Plains. In particular, the 12Z ECMWF and UKMET and
00Z GFS are reasonably similar and have good support from ensemble
members. However, after 06.12Z (into the Day 3 QPF period), the
UKMET does begin to shift a surface low much further east along
the Gulf Coast than the GFS and ECMWF and their ensemble means.
Therefore, less weight was placed on the UKMET beyond Thursday
morning. The 00Z NAM and 12Z CMC seem to show a faster progression
of the trough than the other deterministic models (with very
little ensemble support), and the swaths of heavy QPF also make
more of an eastward progression by Thursday than the other models.
Those two models are not included in the model preference.


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

Lamers