Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1239 PM EDT Tue Oct 09 2018

Valid Oct 09/1200 UTC thru Oct 13/0000 UTC

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

12Z Model Evaluation...with latest preferences and confidence
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...Overall Pattern Across the CONUS... 
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Preference: Blend of the 12Z GFS and 00Z ECMWF/UKMET
Confidence: Slightly above average

The upper level pattern across the CONUS remains highly amplified
featuring an anomalous subtropical ridge off the Mid-Atlantic
coast (+2.5 SD) to a deep longwave trough over the southern Plains
(-3.5 SD) and another ridge over the Pacific. Through the forecast
period (12z Saturday), the longwave trough will lift toward the
Upper Midwest, becoming positively tilted while energy from the
Pacific NW begins to phase with it. By Friday into Saturday,
additional shortwaves will traverse the northern tier US as
general troughing encompasses much of the CONUS. At the surface,
low pressure over the southern/central Plains will deepen and
accelerate toward the Upper Great Lakes region while a large dome
of high pressure builds in its wake.

In general, the suite of model guidance is in reasonable agreement
with the major features across the CONUS, outside of the west
coast by Friday/Saturday. There are some minor differences with
the longwave trough position and strength by Wednesday evening
across Minnesota, likely due to how quickly the northern and
southern stream energy phases. The 12z NAM is a bit stronger and
more pronounced with the tilt of the shortwave, closing off over
the Dakotas (similar to the 00z CMC). Meanwhile, the 12z GFS lines
up well with the 00z ECMWF/UKMET, keeping the trough more open as
it lifts through the northern tier. With the surface low track
across the Upper Midwest, the 12z GFS and NAM line up well with
the rest of the guidance.

Off the California coast by Friday into Saturday, there are
differences in the upper levels how the trough evolves and
possibly interacts with the remnants of Sergio. The 12z GFS/NAM
were slower, more pronounced and further north with a 500 mb
closed low forming well off the coast, compared to the ECMWF which
is more progressive and almost inland. The 00z CMC lies in between
of these solutions. But there is some higher uncertainty with this
feature compared to the rest of the CONUS.

Based on the latest model spread and clustering of solutions
across the CONUS for this period, except for the West Coast on day
3, a blend of the 12Z GFS with the 00z ECMWF and UKMET solutions
will be preferred.

...Hurricane Michael...
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Preference: See the latest NHC forecast advisory

The latest guidance agrees well in the near term, taking Hurricane
Michael northward then north-northeastward into the FL Panhandle
Wednesday afternoon/evening. The storm's track will then becoming
more northeasterly as it treks across southern GA into the
Carolinas. Differences in the guidance creep up with forward
speed, as the latest GFS trended slower (similar but not quite as
slow as the ECMWF) compared to previous cycles. The current NHC
forecast advisory is a compromise between the latest GFS solution
and the UKMET, perhaps leaning closer to the GFS solution for now.
Please consult the latest NHC forecast advisory for more details
on Hurricane Michael.

...Hurricane Sergio...
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Preference: See the latest NHC forecast advisory

Fairly tight clustering in the global models with the forecast
track of Sergio, as it accelerates northeast toward the central
Baja California peninsula over the next few days. The UKMET is a
faster solution, while the ECMWF/CMC on the slower side of the
spread. The current advisory lies about halfway between the GFS
and ECMWF solutions, though the GFS circulation is likely a bit
too strong off the Baja California. Please consult the latest NHC
forecast advisory for more details on Hurricane Sergio.


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

Taylor