Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
243 AM EDT Thu May 30 2019

Valid May 30/0000 UTC thru Jun 02/1200 UTC

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

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

...Overall Pattern Across the CONUS...

Preference: General Model Blend
            Less weight to 12Z UKMET, 00Z NAM
Confidence: Average

---06Z UPDATE---
No change to the preliminary preference. 00Z models remained
relatively consistent with the previous model cycle.

---PREVIOUS DISCUSSION---
The greatest sources of model spread over the next few days in and
near the CONUS are associated with (1) a strong upper level closed
low over Nunavut that will dig as a shortwave into the western
Great Lakes this weekend, AND (2) the trough currently over the
Midwest that will eject east into the Mid Atlantic on Friday.
Otherwise, model mass fields are in reasonably good agreement.
Over the West, ECMWF ensemble spread for 500mb heights is well
below the previous 30-day average.

Despite the aforementioned differences, there are not large
variations between model QPFs. Overall, QPF maxima are placed in
similar locations and the magnitudes are similar. The greatest
differences seem to be in the Great Lakes region, and are likely
due to the model spread with the two features described above.

With those two features, the 00Z NAM and 12Z UKMET exhibit the
largest deviations from the median model and ensemble means. By
02.12Z, the NAM shows generally lower heights across much of the
central and eastern CONUS as compared to the other deterministic
models. And the UKMET shows a significantly stronger and faster
wave in the western Great Lakes, with more substantial ridging
over the High Plains. Less weight was placed on those models given
less ensemble support. The UKMET in particular is near outer edges
of envelope of ensemble forecasts in some cases.

The model preference is for a general model blend, with less
weight to the NAM and UKMET. The overall lean is toward a mixture
of the ECMWF and GEFS ensemble means, which is similar to a blend
of the GFS, ECMWF and CMC.

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

Lamers