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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0702Z May 23, 2018)
 
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Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
302 AM EDT Wed May 23 2018

Valid May 23/0000 UTC thru May 26/1200 UTC

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

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

...Trough digging across the Northeast through Wednesday...
...Surface low crossing the Northeast...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

The guidance depicts an amplification of a northern stream trough
across the Northeast through Wednesday as a surface wave ejects
across the interior of the Northeast along a front settling
southeast across the region. There is good agreement seen out of
the models and so a general model blend will be preferred.


...Large scale trough/closed low impacting the West...
...Energy crossing the northern High Plains by Thursday...
...Arriving across the Upper Midwest Friday and Saturday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

The models take the closed low feature over the Intermountain West
and advance it off to the northeast on Wednesday, and the energy
should eject up over the northern High Plains on Thursday. By
Friday and Saturday, the closed low should weaken into a
progressive trough axis that will cross the Upper Midwest. The 00Z
UKMET slowed down just a little more from its previous run and is
close to the model consensus. Will recommend a general model blend
as a result.


...Mid level trough currently over the Southeast...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

The guidance is in very good mass field agreement with this
system, so a general model blend will be preferred.


...Upper trough/closed low offshore the West Coast by Wednesday
and Thursday...
...Closed low moving inland across CA on Friday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
Preference: General model blend
Confidence: Above average

The models drop another upper trough and associated closed low
feature south down off the West Coast by Wednesday and Thursday,
and then eject this system eastward across CA on Friday. The
guidance is rather well clustered on the progression of this
system, so a general model blend will be preferred.


...Weakening shortwave/front approaching the Pacific Northwest
late Friday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-CMC blend
Confidence: Above average

The models bring a weakening shortwave trough and associated cold
front in toward British Columbia and the Pacific Northwest by late
Friday. The 00Z CMC by the end of the period is a bit slower with
the shortwave. The remaining guidance is well clustered and so a
non-CMC blend will be preferred.


...Surface low development over the Gulf of Mexico by Friday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of the 00Z ECMWF and 00Z CMC
Confidence: Below average

The latest deterministic guidance and ensemble plots again are
rather strongly in favor a low to mid level low center evolving
near or north of Yucatan Peninsula by Friday that will be lifting
north toward the central Gulf of Mexico by Saturday. The 00Z NAM
is the deepest and also fastest solution. The 00Z ECMWF and 00Z
CMC are a bit slower and not as deep, but the CMC leans toward the
deeper side of the model suite. The CMC tracks the system a little
east of the ECMWF also. The 00Z GFS is farthest to the east with
the low and has the system over far western Cuba by the end of the
period. Meanwhile, the 00Z UKMET is the slowest and farthest south
with the system still over the western Caribbean Sea on Saturday.
The GFS and UKMET have very little ensemble support for their
respective solutions at least for this period and will be
discounted as the majority of European, Canadian and GEFS members
have the low somewhere over the central or eastern Gulf of Mexico
on Saturday with several members that are actually well north up
near the central Gulf Coast. The preference will be toward a blend
of the ECMWF and CMC as a means of compromising on location and
intensity. This will also be near the middle of the ensemble
spread.


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

Orrison