Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1234 PM EDT Sun Jun 03 2018

Valid Jun 03/1200 UTC thru Jun 07/0000 UTC

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

12Z NAM/GFS evaluation with preliminary preferences


...Departing upper trough over the Mid-Atlantic coast today...
...Coastal low off of the northern Mid-Atlantic/New England coast
through Tuesday morning...

Preliminary Preference: 12Z GFS/00Z ECMWF blend
Confidence: Average

Upper trough across the Mid-Atlantic today is expected to move
eastward by tonight, with the associated surface low tracking
northeastward off the Mid-Atlantic/Northeast coast. Models handle
the upper wave similarly, and the most significant differences are
with the track of the surface low off the coast by late Monday.
The NAM and 00Z UKMET were on the left side of the spread by 00Z
Tue, while the 12Z GFS and 00Z ECMWF were very close to a
relatively tightly clustered ensemble consensus. Thus, a blend of
the 12Z GFS and 00Z ECMWF is preferred.


...Negatively titled upper trough crossing the Great Lakes today
with likely closed low over southeastern Canada Tuesday morning...
...Additional surface low developing along the Mid-Atlantic coast
by late Tue...

Preliminary Preference: 00Z ECMWF
Confidence: Average

Models handle the trough/upper low similarly through Tue. The 12Z
NAM is slightly more amplified than consensus with the trough axis
across the Ohio Valley/Appalachians by 00Z Wed and this continues
as the trough moves offshore. As another surface low develops
across the northern Mid-Atlantic region late Tue, models show a
range of solutions primarily with respect to timing as the feature
moves northeastward off the coast. The 12Z NAM is on the slow side
of the spread while the GFS is on the fast side. The 00Z ECMWF was
the solution most closely aligned with an ensemble-based
consensus, and is the preferred solution at this time.


...Shortwave over the Southwest U.S. today, reaching the Plains on
Monday...

Preliminary Preference: 00Z ECMWF
Confidence: Average

Models handle this feature similarly initially as the feature
crosses the Four Corners region through tonight. By Mon as the
wave reaches the plains, the NAM is the most amplified of the
deterministic solutions while the GFS makes up the least amplified
side of the spread. The 00Z ECENS/NAEFS means both support
something in between these two extremes, closest to the 00Z ECMWF,
which is the preference at this time.


...Upper level troughing along the West Coast through Tuesday...

Preliminary Preference: GFS/00Z ECMWF blend
Confidence: Average

A series of mid/upper-level shortwaves will traverse a broader
upper trough, reaching the West Coast starting later today. The
evolution of this is a bit complex, with one of the shortwaves
quickly crossing the northern Rockies and reaching the northern
plains by Wed morning, while energy and a trough axis linger along
the West Coast as well. Models generally handle these features
similarly through Monday. As the energy ejects east across the
northern Rockies/plains Tue-Wed, models show some small timing and
amplitude differences, with the NAM seemingly underamplified, and
the 12Z GFS/00Z ECMWF showing a similar amplitude but minor timing
differences. The GFS/00Z ECMWF also show similar solutions with
the trough axis lingering along the West Coast into mid-week. Thus
will recommend a blend of these two solutions at this time.


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

Ryan