Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1244 PM EDT Fri Jul 24 2020
Valid Jul 24/1200 UTC thru Jul 28/0000 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
12Z Model Evaluation Including Preferences and Forecast Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...Mid-upper level troughing tracking from the Northwest into the
north-central U.S. through the weekend...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend...through 60 hours
12Z GFS/00Z UKMET/00Z ECMWF blend...after 60 hours
Confidence: Average
A mid-level closed low/shortwave trough will track through
southwestern Canada through Saturday with a cold front at the
surface and extending into the northwestern U.S. As this energy
reaches the northern Plains late in the weekend, it will phase
with some southern stream energy lifting through the Front Range
and central Plains, which will allow the trough to deepen over the
northern Plains and upper Midwest. The latest guidance is in good
agreement through about 60 hours, with some tendency for the 00Z
CMC to lag the remaining guidance with its height fall progression
thereafter. Also, the 12Z NAM after 60 hours may be a tad too
strong with its trough over the upper Midwest. So, a general model
blend will be preferred through 60 hours, followed by a blend of
the well clustered 12Z GFS/00Z UKMET and 00Z ECMWF thereafter.
...Tropical Storm Hanna...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Official NHC track
Best Model Proxy: 12Z GFS/00Z UKMET and 00Z ECMWF blend
Confidence: See latest NHC products
The latest model guidance continues to show fairly good clustering
with the track and speed of the T.S. Hanna over the next 24 hours
as the system approaches and ultimately makes a landfall along the
south-central Texas coastline. The 12Z GFS and 00Z ECMWF are
generally close or perhaps locally a tad south of the 15Z NHC
track of Hanna, with the 12Z NAM and 00Z CMC a bit farther north
leading up to landfall. The 00Z UKMET is quite close to the latest
NHC track. Overall, the NAM appears to be too fast with the
forward speed of Hanna, with the CMC too slow. Some strengthening
of the mid-level subtropical ridge north of Hanna should steer the
system more westward by Saturday and then west-southwestward
Saturday night as the system crosses through the lower Rio Grande
Valley. On Sunday, Hanna should be weakening over northeast
Mexico.
...Upper low/trough over California...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average
A broad upper trough and embedded closed low over CA will
generally remain in place through early next week, with some
tendency for the energy to begin lifting north by the end of the
period. Overall, the models are in good agreement through the
period with the handling of this energy, so a general model blend
will be preferred.
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
Orrison