Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
121 AM EST Mon Mar 04 2019
Valid Mar 04/0000 UTC thru Mar 07/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
00Z Model Evaluation Including Preference and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend
Confidence: Slightly above average
07z update: No significant changes in the 00z UKMET/CMC/ECMWF
further support the initial thinking of general model blend.
---Prior Discussion---
Large scale model agreement continues to solidify especially with
the vast global scale cyclone over the eastern half of the
continent. Internal waves show similar depth and timing even as
the vortex breaks down into Wed/early Thurs with some mild spread
in eastern Canada with limited affects in the Northeast CONUS.
The West there is more substantial spread especially by day 3,
mainly in multiple stream mid-troposphere interactions/"Fujiwara".
The main QPF driver is a southern stream shortwave emanating out
of the Central Pacific today approaching CA late Tuesday into Wed.
While there are some interaction with the closed low to the north
(described below), it is minor allowing typical progression into
CA, terrain and through the Intermountain West by late Wed/early
Thursday. The 12z ECMWF is a shade further north with the inner
core of the upper low, allowing increased interaction with the
northern stream, breaking down the cyclone as a whole through the
Intermountain West. By Thursday the GFS/CMC are a bit faster with
the wave lifting into the Plains, but again this appears minor to
support a general model blend here as well at slightly above
average confidence.
The greatest mass differences remain in the Pacific Northwest,
where there is limited moisture to lead to only minor QPF
differences Wed into Thurs. The closed low over S BC will dance
with another compact wave out of the NE Gulf of AK late Tuesday,
there has been growing consensus with this binary interaction with
the GFS trending faster with the 18z run and maintaining at 00z.
The NAM is the slowest, while the UKMET is fastest. The main
difference by Wed is the EC/CMC trending west (favoring the
northern vort center) while the GFS/UKMET press height-falls a bit
east in WA, which in turn slides QPF a bit east. A compromise
between camps appears appropriate and in line with overall
ensemble mass trends.
Further model spread occurs as initially the GFS, followed by the
NAM break down the Gulf of AK ridge and blast strong shortwave
height-falls SE stretching the upper low over SW BC into a SW-NE
elongation into the Pacific. There is limited support for this
magnitude/timing of breaking down the ridge even with GEFS
ensemble members (as well as ECENS/CMCE members). So would be
favoring something closer to UKMET/CMC/ECMWF blend for this area
with a more concentric closed low. This is still upstream of the
CONUS and blends into preferences by WPC medium-range forecasts
(please refer PMDEPD).
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Gallina