Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
126 AM EST Thu Dec 26 2019
Valid Dec 26/0000 UTC thru Dec 29/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
00Z Model Evaluation with preferences/confidence intervals
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NAM/GFS initialization errors do not seem to degrade their short
range forecasts.
System approaching Pacific Northwest Sunday morning
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Preference: Non-NAM compromise
Confidence: Above average
There are competing factors clouding the forecast picture across
the Pacific Northwest and Plains/Midwest by Sunday. A system
approaching the Pacific Northwest at that time has a building
ridge seen in all the guidance in its wake, which should yield a
strengthening system aloft moving towards the region, which the
00z guidance is trending toward. The 00z NAM has a strong leading
shortwave moving by western WA Saturday night that looks a bit
weaker in the other guidance (weaker is a better fit to the
synoptic pattern in which it is embedded). A compromise of the
00z GFS/00z UKMET/00z ECMWF/00z UKMET looks ideal with the
Northwest system with above average confidence.
System moving from the West into the Midwest Fri-Sun
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Preference: ECMWF/UKMET/Canadian compromise
Confidence: Slight Above Average
Downstream, the guidance is plagued with stream interaction as the
system moving from the West into the Plains starts out unphased
but becomes phased with time as a sharply amplified ridge building
into western Canada. The quickest solutions with the
Plains/Midwest system are the 00z GFS and 00z NAM -- the other
guidance is a bit slower. Since the flow overall is becoming more
amplified, a slower solution in the Plains/Midwest is preferred by
Sunday morning since the kicking influence of the system
approaching the Pacific Northwest shouldn't be felt quite yet
(over 15 degrees latitude/900 miles away). Prefer a compromise of
the 00z ECMWF/00z UKMET/00z Canadian with the Plains/Midwestern
system with slightly above average confidence.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Roth