Prognostic Meteorological Discussion
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428
FXUS10 KWNH 191714
PMDHMD

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
113 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 NAM/GFS evaluation...with preliminary 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/00Z ECMWF
Confidence: 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. At
the surface however, the ensemble means agree best with a 12Z
GFS/00Z ECMWF blend with the 00Z UKMET a close second option
through about 12z/22. However, the 00Z UKMET has a stronger wave
over New England by 00Z/23 which is not supported in the model
consensus and appears a bit fast. 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.


...Mid level trough developing over the eastern Gulf of Mexico by
Sunday...
...Lifting up across the Southeast on Monday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of the 12Z GFS and 12Z NAM
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 00Z ECMWF is weakest with this system and the 00Z UKMET is
strongest in the mid-levels. 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 appraoch led by a blend of the non-00Z ECMWF guidance,
but mostly the 12Z GFS and 12Z NAM. Overall, differences at the
surface are not too large.


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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