Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
243 PM EDT Sat Jun 15 2019

Valid Jun 15/1200 UTC thru Jun 19/0000 UTC

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

12Z Final Model Evaluation...with Confidence and Preferences
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...Overall Analysis Across the CONUS...
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Preference: 12Z GFS, 12Z NAM, 12Z ECMWF
Confidence: Slightly Above Average

---18Z UPDATE---
No change to the preliminary preference. The CMC continues to be
faster with the shortwave pushing into the Ohio Valley and Mid
Atlantic, and the UKMET continues to have higher heights through
the Midwest and South.

---PREVIOUS DISCUSSION---
Models are in fairly good agreement across much of the northern
tier of the country (with a relatively persistent, broad trough)
and across the West (with a strong ridge building on to the West
Coast). Greater variability exists in the Midwest, Ohio Valley and
South, where rainfall is expected to be primarily driven by
convection. Some of this is the typical convective variability,
but there are additional differences related to the strength of
primary shortwaves embedded in the flow.

A strong MCV was noted on satellite over eastern Missouri.
Generally, the 12Z NAM and GFS have led the model trend with a
stronger shortwave in this area, while the 00Z ECMWF was weaker
and still trending in that direction. All of the models have a
coherent shortwave continuing east into the Mid Atlantic through
Sunday, however the NAM and GFS may best capture the strength of
the wave.

A second shortwave was situated over New Mexico and is expected to
gradually make progress east toward the Ohio Valley by Tuesday.
The 00Z UKMET seems to shear out a lot of the shortwaves in this
region of the country, and as a result has higher heights than all
the other deterministic models and many of the ensemble members.
This has been consistent over the past few runs, but given the
lack of ensemble support, the UKMET is excluded from the
preference. Additionally, the 00Z CMC seems to speed up the
shortwave much more than the other models by Tuesday, and
similarly has limited ensemble support. Therefore it is also
excluded from the preference.

The NAM, GFS, and ECMWF have reasonably similar timing of this
feature. However, the NAM and GFS are stronger (possibly due to
convection). There is also additional uncertainty about a
secondary shortwave or MCV developing ahead of the primary wave.
All three models show a separate vorticity maximum developing
ahead of the shortwave by tonight, but the ECMWF quickly weakens
it while the GFS and NAM show it propagating downstream. There is
no clear preference of the NAM/GFS versus the ECMWF in this
region, and a blend should account for some of the inherent
uncertainty better.


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

Lamers