Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
155 AM EDT Fri Jun 29 2018

Valid Jun 29/0000 UTC thru Jul 02/1200 UTC

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

00Z NAM/GFS model evaluation...including preliminary preferences
and confidence
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...Western U.S. to the Northern Plains and Upper Great Lakes...
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Preference: Blend of the 00Z GFS/12Z ECMWF
Confidence: Average

A mean longwave trough initially anchored over the western U.S.
will gradually advance eastward while a potential disturbance well
south of El Paso, Texas should lift poleward toward the Southern
High Plains. Some of the most pronounced differences reside with
the longwave trough, particularly with timing and depth. 582-dm
ensemble spaghetti plots show 12Z ECMWF ensemble members in
advance of the slower 12Z GEFS solutions with such issues not
showing in prior model cycles. Considering other models, the 00Z
NAM stands out as a slow outlier early on with the 12Z CMC
eventually taken a slower path by Day 3 across the Middle
Mississippi Valley. The resultant differences aloft also reflect
at the surface as a wavy frontal zone arcs southwestward from the
Upper Great Lakes back to the Central Plains. Will see what the
00Z ECMWF does, but for now will take a split of the 00Z GFS/12Z
ECMWF solutions.


...Eastern U.S....
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Preference: Blend of the 00Z GFS/12Z ECMWF
Confidence: Average

As a shortwave trough exits into the western Atlantic, models are
in solid agreement about developing a large 594-dm mid-level ridge
across the mid-Atlantic. Underneath this, a slowly meandering
bundle of vorticity should retrograde from the southeastern U.S.
coast back toward the Florida panhandle. Model spread is on the
lower side with its position accompanied by general agreement on
well above average precipitable water values over the eastern Gulf
Coast. The 00Z NAM and 12Z CMC/UKMET show some impressively high
QPF values by Day 3 which will be of interest in the Excessive
Rainfall Outlook. Will play the more conservative approach with
the pattern leaning more toward the 00Z GFS/12Z ECMWF solutions.


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

Rubin-Oster