Prognostic Meteorological Discussion
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000
FXUS10 KWNH 200638
PMDHMD

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
237 AM EDT Sun May 20 2018

Valid May 20/0000 UTC thru May 23/1200 UTC

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

00Z model evaluation...with preferences and confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Shortwave trough exiting the East through early Sunday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

The models show similarly with this system.


...Upper trough/cold front crossing the Northeast...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

The models show similarly with this system.


...Upper trough/closed low over the central Plains today and
crossing the Midwest by Monday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend
Confidence: Average

The guidance is finally fairly well clustered with the evolution
of this system, but there are still differences of note. The NAM
gradually becomes a little slower and deeper than the global
models as the energy crosses the Midwest. Regarding the global
models, there is notably better agreement as the ECMWF has slowed
down a little more and also the CMC and UKMET have clustered
toward the GFS solution. Based on the latest trends and
clustering, a non-NAM blend will be the preference.


...Upper trough digging into the West on Sunday...
...Closed low digging into the Southwest Monday and Tuesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

The models continue to show very good agreement with the mass
field evolution of this system with only some very modest depth
spread noted toward the end of the period. Will prefer a general
model blend.


...Mid level trough over the eastern Gulf of Mexico...
...Lifting up across the Southeast on Monday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Slightly above average

The models gradually take a rather broad mid level trough and
associated closed low up across the eastern Gulf of Mexico and
into the Southeast U.S. over the next couple of days. The guidance
has come into generally good agreement on just a weak surface
reflection with an inverted trough. Model spread is rather minimal
at this point as the CMC has trended slower and in line with the
remaining guidance. Thus, will prefer a general model blend.


...Shortwave energy/vorts lifting across the Plains Tuesday and
Wednesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of the 00Z UKMET and 00Z ECMWF
Confidence: Average

Multiple shortwave impulse are expected to lift northeast out of
the base of the Western U.S. trough and across the Plains on
Tuesday and Wednesday. The NAM and GFS are both rather aggressive
with their respective vorts and appear too strong considering that
the energy will be lifting northeast into a mean layer ridge.
There is evidence of convective feedback over deepening this
energy on both models. The CMC, UKMET and ECMWF all appear more
reasonable with the strength of their vorts, although the CMC does
look too deep with the energy it has over MN/IA at the end of the
period. Will favor a UKMET/ECMWF blend in general with the energy
attempting to eject out across the Plains Tuesday and Wednesday.


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

Orrison

$$





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