Prognostic Meteorological Discussion
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000
FXUS10 KWNH 110711
PMDHMD

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
311 AM EDT Sat Jul 11 2020

Valid Jul 11/0000 UTC thru Jul 14/1200 UTC

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

00Z Model Evaluation with Final Preferences/Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Mid-level shortwave crossing the Great Lakes/Ohio Valley
through Sat...
...Associated cold front crossing the Great Lakes...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Average

The models show minor differences in the timing and strength of
the low to mid-level wave advancing through the Northeast
today/Saturday night. The new 00Z UKMET scaled back its previously
stronger depiction of the 700-500 mb low which was unsupported in
the remaining guidance. Therefore, a general model blend will work
well for this system.


...Tropical Depression Fay...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: non 00Z NAM blend is closest to 03Z NHC advisory
Confidence: refer to NHC discussion

The latest guidance is in good agreement concerning the track of
Fay until late Saturday when the 00Z NAM deviates west of the NHC
track. The difference is relatively minor when compared to the
remaining 00Z deterministic guidance, but enough to exclude it
from the preference at this time concerning the track of Fay.


...Mid-level shortwave to cross the northern Plains to Upper MS
Valley Sat, Ohio Valley Sunday,
Great Lakes to the Appalachians Monday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Near the 00Z UKMET/00Z CMC/12Z ECMWF mean/00Z GEFS mean
Confidence: Slightly below average

The models begin to diverge with the timing of the trough as it
reaches the OH Valley. The 00Z NAM and 00Z GFS are faster,
especially the 00Z GFS when compared to the remaining
deterministic guidance and the GEFS/ECMWF means. The 00Z UKMET/CMC
sped up their timing relative to their 12Z cycles which is a good
move. Poor run to run consistency exists with this feature as it
reaches the Northeast by Tuesday morning in many of the models
given a very complex interaction of vorticity maxima in
Ontario/Quebec which leans the preference toward the middle ground
of the ensemble means. The closest to the means is the 00Z UKMET
and 00Z CMC at this time.


...Longwave trough axis moving into western Canada and the
northwestern U.S. on Sun...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: non 00Z NAM blend
Confidence: Average

The models show a broad 500 mb trough and associated surface cold
front moving across the Pacific Northwest and Northern Rockies
Sunday to Sunday Night and Northern Plains Monday. Mainly minor
timing differences were noted in the latest guidance, but the 00Z
NAM differs with the core of the closed low that tracks through
Alberta and Saskatchewan when compared to the remaining
deterministic and ensemble mean guidance. This has some impacts
with the NAM`s timing over the Northern Plains as a cold front
sweeps through the region Monday into Tuesday.


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

This product will terminate August 15, 2020:
www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination.
pdf

Otto

$$





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