Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
331 PM EDT Thu Jun 25 2020
Valid Jun 25/1200 UTC thru Jun 29/0000 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
12Z Model Evaluation Including Preferences and Forecast Confidence
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Closed low over Ontario/Quebec
Trough crossing the eastern U.S.
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Preference: 12Z GFS/00Z CMC/12Z ECMWF blend
Confidence: Slightly above average
The 12z GFS/12z Canadian/12z ECMWF are close to the consensus with
the surface closed low as it tracks across Ontario and Quebec.
The 12z UKMET and 12z NAM develop a low crossing the Great lakes
and northeast and have been joined by the Canadian/ECMWF/GFS. With
support from the ECMWF Ensemble Mean and GEFS/SREF Means, prefer
the cluster of the 12z GFS/ECMWF/Canadian global. The forecast
confidence remains slightly above average.
Strong shortwave trough over the Pacific Northwest Sat night/early
Sun-Northern Rockies/Great Basin/northern high Plains Sunday
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Preference: Blend of 12z ECMWF/12z GEFS Mean.
Confidence: Slightly Above Average
The models cluster well in developing a 700 mb closed low in
Washington state 12z Sun, moving it southeast to near southern ID
or adjacent bordering states 00z Mon. The spread grows on Sunday,
with north to south differences and typical timing differences.
The 12z NAM lowers height further north than the majority, and the
12z GFS further south. The 12z GEFS Mean/06z GFS and 12z ECMWF
form the middle of the suite of guidance solutions 00z Mon.
The surface front sags southeast across the Great Basin and
northern Plains Sunday with waves of low pressure along the front.
Modest timing differences exist, as well as strength of low
pressure centers as well. A general model blend would work to
resolve differences, with more weight on the 12z ECMWF/12z
Canadian/12z GEFS Mean.
Texas to the ARKLATEX
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Preference: 12Z GFS/12Z CMC/12Z ECMWF blend
Confidence: Slightly above average
As high pressure sfc/aloft builds west across the Gulf coast
states, the 700 mb wave in Texas drifts west. The 00-12z UKMET
has a stronger anticyclone in Fl/Gulf, so it creates stronger
height rises in TX/ARKLATEX. Fri afternoon. Overall, there is
fairly good clustering in the mid level flow. Based on this, a
general model blend is preferred, with slightly above average
confidence.
...Low forming north of MT 12z Sat and moving into Saskatchewan
and Manitoba...
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Preference: Blend of 12z NAM/00z ECMWF
Confidence: Average
The 12z NAM/00z ECMWF/12z GFS/00z UKMET/00z ECMWF ensemble mean
cluster well with low pressure north of the MT border 12z Sat.
Solutions start to spread as the low moves northeast towards the
Manitoba border. The 12z GFS has slower timing at 00z Sun to 12z
Sun. The 12z UKMET and 12z Canadian global axis of low pressure is
further south, and 12z ECMWF further north. With better
clustering among the 00z ECMWF/ECMWF Ensemble Mean and NAM, a
blend of these solutions is preferred. Confidence is lower in the
UKMET since it changed solutions from the 00z-12z run.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Petersen