Prognostic Meteorological Discussion
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FXUS10 KWNH 191832
PMDHMD

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
231 PM EDT Sat May 19 2018

Valid May 19/1200 UTC thru May 23/0000 UTC

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

12Z model evaluation...with final preferences
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Broad upper trough and embedded MCVs over the East through
Sunday morning...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

The models show similarly with this system.


...Upper trough crossing the upper Midwest today/tonight...
...Cold front/surface wave crossing the Great Lakes/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: Blend of the 12Z GFS/12Z ECMWF
Confidence: Slightly below average

Convergence continues with this system aloft, but detail
differences remain both aloft and at the surface. The 12Z NAM is
slowest with the 500 mb reflection of the shortwave while the 00Z
ECMWF is fastest with the leading edge of the mid-level wave. The
12Z ECMWF slowed down relative to its previous cycle, such that
better agreement is seen in the 12Z deterministic model suite.

At the surface, the ensemble means agree best with a 12Z GFS/12Z
ECMWF blend with the 12Z UKMET/CMC suppressed/weaker/south with
the main surface low tracking into the Ohio valley. Given the weak
nature of the system as it moves east, detail differences continue
to make for a below average confidence level.


...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 show remarkable agreement with this system through the
short range period with little overall spread in the
deterministic/ensemble guidance. Some minor timing differences
show up by 00Z/23Z, but spread is small enough at this time to
prefer a general model blend.


...Mid level trough developing over the eastern Gulf of Mexico by
Sunday...
...Lifting up across the Southeast on Monday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: non 12Z CMC blend
Confidence: Average

The models develop a weak mid level trough and possible closed low
over the eastern Gulf of Mexico along with a weak surface low/wave
by late Sunday which then lifts up across the Southeast on Monday.
The 12Z ECMWF trended toward the consensus regarding the strength
of the low-mid level reflection of this system compared to the
weaker 00Z ECMWF. The ensemble scatter low plots continue to show
very little support for a defined surface low, but none of the
deterministic guidance shows a closed isobar around their surface
low forecasts. Therefore...will prefer a consensus approach
excluding the 12Z CMC given the CMC is much quicker to thrack the
low to the north compared to the remaining available guidance.


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

Otto

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