Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
233 AM EDT Mon Jun 03 2019

Valid Jun 03/0000 UTC thru Jun 06/1200 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 12Z ECMWF and 00Z GFS;
            Slightly greater weight to the ECMWF
Confidence: Average

---06Z UPDATE---
No change to the preliminary preference. The 00Z GEFS Mean
continues to show a less amplified ridge in the central US
downstream of the ejecting trough from the Southwest. This is
closer to the ECMWF than the deterministic GFS. Therefore, a
GFS-ECMWF blend with a lean toward the ECMWF continues to be
preferred.

---PREVIOUS DISCUSSION---
The pattern over the CONUS will be dominated by relatively zonal
flow and low amplitude waves over the northern tier of states, and
a trough over the Southwest that will be ejecting east toward the
central and southern Plains by mid-week. The model preference is
for a blend of the ECMWF and GFS, with some inclusion of the
respective ensemble means. This provides good continuity with the
previous model preference, and a forecast with fairly good
ensemble support.

For the northern stream, models show excellent agreement in timing
and longitudinal placement of waves, but there is some north-south
spread in the height fields. This appears to be somewhat related
to the southern stream trough; models with stronger downstream
ridging from that trough also show higher mid-upper level heights
closer to the Canadian border. This includes the 12Z UKMET and 00Z
GFS and NAM. These models are on the stronger end of model spread
for ridge strength over the Midwest, with better ensemble support
for the ECMWF. Therefore, a slight lean toward the ECMWF is
preferred. The NAM is also excluded from the preference. It shows
convectively induced vorticity maxima developing in the northern
Plains and then propagating downstream leading to very focused and
significant swaths of rainfall.

Further south, the greatest uncertainty continues to be associated
with the interaction of an area of low pressure in the western
Gulf of Mexico and the ejecting trough from the Southwest. The
UKMET was near the outer extent of the model envelope with the
strength of the downstream ridge over the Midwest and Southeast,
and generally shows a faster northward motion of the Gulf low (and
thus a faster interaction). This is not preferred at this time
given limited support from other models. The NAM, by contrast,
stalls the Gulf low around 23N without much additional progress.
This also does not have much model support. Finally, the CMC shows
a much more focused surface low over the Gulf that is both faster
and much further east than other models (with similarly limited
model support). Therefore, the preference is for a blend of the
GFS and ECMWF which most closely match the ensemble means and have
the greatest ensemble support at this time.


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

Lamers