Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
106 PM EDT Sat Sep 01 2018

Valid Sep 01/1200 UTC thru Sep 05/0000 UTC

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

00Z model evaluation...with latest model preferences and confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: General model blend...led by 12Z GFS/00Z ECMWF
Confidence: Average

Across the lower 48, ridging will remain over the Mid-Atlantic
region with mean troughing over the western U.S. through Tuesday.
Across the Gulf of Mexico, a couple of easterly waves are expected
to track west, one currently along the central Gulf Coast and a
second across Florida on Monday.

Up north, there is generally good agreement with timing of
shortwaves and placement of a frontal boundary extending through
the Great Lakes into the upper Midwest. Another cold front is
forecast to reach the northern Plains on Tuesday, meeting up with
the tail end of the upper Midwest boundary. Mass field differences
are relatively minor with these systems, with a blend of the 12Z
GFS/00Z ECMWF a decent compromise of the smaller scale differences.

Across the Gulf of Mexico, the 12Z NAM stands out with hanging
back the 1st wave along the western Gulf Coast on Monday into
Tuesday while the remaining consensus takes the mid-level energy
north into the southern Plains. Not going with the 12Z NAM across
the Gulf is preferred given a lack of support for its solution.

The second wave near Florida for early in the week shows some
placement and timing differences with the mean position in the
guidance nearest to a blend of the 12Z GFS/00Z ECMWF. The 00Z
ECMWF is much stronger compared to the 12Z GFS, but a blend of
position and strength is preferred at this time with ensemble
scatter low plots showing some weak support for a defined low,
similar to the 00Z ECMWF. The NHC is highlighting a 40 percent
chance of tropical cyclone formation for this system through the
middle of next week, so please refer to NHC products for the
latest updates on this system.

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

Otto