Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
211 PM EST Thu Dec 05 2019
Valid Dec 05/1200 UTC thru Dec 09/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation with Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of 12Z ECMWF, 00Z ECMWF Ensemble Mean;
12Z NAM included outside of the West Coast
Confidence: Slightly above average
---18Z UPDATE---
No change to the preliminary preference. The 12Z ECMWF is very
well aligned with the prior 00Z ECMWF Ensemble Mean, and the 12Z
UKMET converged closer to the ECMWF along the West Coast.
---PREVIOUS DISCUSSION---
Model agreement is still relatively good overall across the CONUS,
particularly through 07.12Z (Saturday morning). However, there are
some important differences that led the model preference to lean
increasingly to a blend of the ECMWF, ECMWF Ensemble and NAM by
this weekend.
The greatest differences exist with the trough approaching the
West Coast. Over the past couple model cycles, the trend has
generally been closer to the ECMWF Ensemble mean and the 00Z
deterministic ECMWF is relatively close to that as well. This
provides a good anchor point to assess the other models. The 12Z
GFS is less amplified and faster with the trough, while the 06Z
GEFS members are much closer to the ECMWF Ensemble mean. The 00Z
CMC has a strong vorticity maximum near British Columbia on
Saturday morning, and that eventually digs south along the West
Coast and influences the pattern evolution. The 00Z UKMET and 12Z
NAM are much slower with the trough and are not supported by many
ensemble members. For these reasons, the preference is for a blend
of the ECMWF and ECMWF Ensemble Mean.
Outside of the West Coast, the 12Z NAM seems to be reasonably
close to the ECMWF and is included in the model preference. The
CMC, UKMET and GFS still show some other differences, with the GFS
much slower with the surface low or wave along the Gulf Coast this
Saturday, and the CMC and UKMET showing much more QPF near the
MN-Ontario border despite a relatively weak, low-amplitude wave.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Lamers