Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1157 AM EDT Tue Jun 25 2019

Valid Jun 25/1200 UTC thru Jun 29/0000 UTC

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

12Z Model Evaluation...with Final Confidence and Preferences
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...Overall Pattern Across the CONUS...
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Preference: GFS/ECMWF blend across northwest/northern tier
            General model blend elsewhere
Confidence: Average

Large scale flow across the CONUS is dominated by mainly zonal
flow with a large closed low anchoring along the NW Coast and
another closed/occluded low going off to die across James Bay/S
Hudson Bay...pressing the cold front off-shore of New England
today (with good model agreement).  The western closed low will
shift south and toward the OR coast slowly filling toward Thursday
with little model difference until very late stage breakdown
shearing across into SW Canada by the end of the forecast period. 
This is always difficult to precisely forecast given the smaller
scale internal waves and their precise magnitude.  The ECMWF/GFS
and their ensemble members favor a slower shearing toward the
northeast into Canada languishing across the western Columbia
River Valley. The 12z NAM/CMC favor more toward the northeast. 
Upstream interaction/flow out of the Gulf of AK should support the
GFS/ECMWF solution (and their ensembles) over the more
transitional NAM/CMC. 

The other significant feature was a subtle
Subtropical/southwesterly flow shortwave that emerges from the
Central Rockies into Thursday.  Here convective development
enhances the wave after topping the ridge into the Upper
Midwest/Great Lakes into Fri.  The 12z NAM and 00 UKMET are very
aggressive with vortex strengthening and convective response,
feeding back onto the wave.  This is not supported give proximity
to the dying but still important closed low over N Ontario...that
should favor more sheared/zonal flow undercutting it.  As such
will favor a GFS/ECMWF/CMC solution for this region as well.

Elsewhere, the subtropical ridge will dominate and the start of a
"Ring-of-Fire" convective pattern will start to emerge.  However,
there is good model agreement in a break in the ridge around
mid-South/central Gulf where some of the convective complex energy
will support a sheared MCV/vorticity center that will string out
and eventually start to retrograde by the end of the forecast
period.  The ECMWF is a bit slower and therefore west with the
weakness relative to the stronger GFS/NAM/UKMET but a general
model blend should suffice as the placement is not dramatically
different for such a small scale/convectively influenced feature.

Overall confidence is just average given the importance/influence
of small scale convectively induced features though large scale
features/flow pattern is slightly to above average in agreement.  


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

Gallina