Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
224 AM EDT Sun Jul 26 2020
Valid Jul 26/0000 UTC thru Jul 29/1200 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
00Z Model Evaluation Including Preferences and Forecast Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...Mid-upper level troughing over the northern CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average
Mid to upper level energy over southern Canada is expected to
close off before settling over Ontario later in the period, while
the larger scale trough deepens over the Great Lakes region. At
the surface, a pronounced cold front is forecast to march across
the northern tier into the Great Lakes while upstream ridging
builds over the Canadian Rockies. In the increasingly amplified
pattern, the models have converged on a similar idea and show very
good agreement through 84 hours with the synoptic pattern.
...Tropical Storm Hanna...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Official NHC track
Best Model Proxy: Non-GFS model blend
Confidence: See latest NHC products
Gradual weakening over land will occur as the system tracks
westward then southwestward into the rugged terrain of Mexico on
Sunday and Sunday evening. The biggest spread in the models occurs
after the system moves into Mexico where the GFS is on the
southern side of the model spread. A CMC/ECMWF/UKMET/NAM blend is
the best proxy to the official forecast and for the latest
information on Hanna, please consult the latest NHC public
advisory.
...New upper trough/low approaching California by Tuesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-UKMET blend
Confidence: Slightly Above Average
Toward the end of day 2 and into day 3, another shortwave trough
approaches the Northwest Pacific and northern CA in all of the
guidance except the 00z UKMET which keeps the southern stream
shortwave in place west of 130W longitude. The 00Z guidance is
otherwise in good agreement showing some slight depth issues with
the northern stream shortwave moving by the Pacific Northwest late
Tuesday. As an approaching upper level low should act as a kicker
for the shortwaves in both streams Tuesday night, believe the 00z
UKMET has no support from the synoptic pattern either. A
compromise of the 00z GFS, 00z Canadian, 00z NAM, and 00z ECMWF is
preferred with slightly above average guidance.
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
Roth/Taylor