Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
226 AM EDT Sun Jun 09 2019

Valid Jun 09/0000 UTC thru Jun 12/1200 UTC

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

00Z Model Evaluation...with Confidence and Preferences
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...Overall Pattern Across the CONUS...
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Preference: Blend of the 00Z GFS and 00Z ECMWF
Confidence: Slightly above average

The blockiness of the upper air pattern across the eastern U.S.
will break down as a deep layer southern stream closed low and
associated trough moves east through the Tennessee Valley and
becomes elongated in a north/south on Sunday while spanning an
axis from the Ohio Valley south to the eastern Gulf coast region.
On Monday, a portion of the trough will actually get suppressed
down to the south and will become focused over the northeast Gulf
of Mexico through Tuesday. The models are in very good agreement
with the mass field evolution of this and the erosion also of the
deeper layer ridge that is currently in place over the Great
Lakes, northern Mid-Atlantic and southern New England.
 
At the surface, the models do still suggest a weak area of low
pressure lingering early Sunday just off the Mid-Atlantic coast
along a frontal zone. The guidance tends to advance the low
northwest and then north-northwest near the Delmarva by Sunday
night. On Monday, what is left of the low should lift north as a
warm front surges north along the East Coast in response to the
eroding ridge axis and also approach of a northern stream trough.
The 00Z NAM and 00Z CMC are on the stronger side of the guidance
with the low center, but the latest 00Z HREF members via the ARW,
NMMB and especially the ARW2 are flatter. The 00Z GFS, 00Z UKMET
and 00Z ECMWF are also flatter than the NAM and CMC. Surface
observations and the latest GOES-16 3.9 micron imagery do already
suggest a weak low center northeast of the NC Outer Banks.
However, the model preference with this system will be away from
the stronger NAM/CMC solutions.
 
Meanwhile, a strong intrusion of northern stream height falls
ejecting out of the Northwest and across the northern Plains and
Midwest will be a facilitator of a larger scale pattern change
across the U.S. All of the guidance shows a trough swinging
through the Great Lakes region by Monday and the Northeast on
Tuesday with additional northern stream shortwave impulses digging
down in behind it across the northern Plains and Midwest in
response to upstream ridging which builds along the West Coast.
The guidance has come into better timing agreement with the
initial surge of height falls across the Great Lakes region and
with the details of the a strong cold front that will cross Plains
and Midwest and eastern U.S. through the period. However, the 00Z
UKMET does get to be a bit stronger and little slower than the
remaining guidance as the upper trough pivots across the
Northeast. Gradually the UKMET slows its surface cold front down
as a result across this region. Additionally, there is some spread
with the additional upstream shortwave energy which begins to dig
across the Midwest late Tuesday through early Wednesday. The 00Z
CMC becomes a bit of a stronger outlier with this energy and
suggests a possible closed low development which the remaining
guidance at least through this period does not depict.
 
Based on all of this, the model preference for the CONUS will be
toward a consensus of the better clustered and ensemble-supported
GFS and ECMWF solutions.


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

Orrison