Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
248 PM EDT Mon May 11 2020
Valid May 11/1200 UTC thru May 15/0000 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
12Z Model Evaluation Including Final Preferences and Confidence
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...Mid-level trough amplifying across the Northeast with
accompanying surface low through Tuesday morning...
...Shortwave moving across the Great Lakes and Northeast Tuesday
and Wednesday...
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Preference: General model blend
Confidence: Above average
...19Z update...
The 12Z CMC adjusted faster, toward the remaining model guidance,
with the lead shortwave and surface low moving through the
Northeast. Given good continuity from the 12Z ECMWF/UKMET, and
overall good agreement in place with the 12Z model suite, a
general model blend is preferred. Regarding the secondary
shortwave, very minor changes were noted with the 12Z
ECMWF/UKMET/CMC compared to their 00Z cycles.
...previous discussion follows...
A lead shortwave moving through the Northeast with an attendant
surface low shows relatively good agreement through Tuesday
morning, but the 00Z CMC is slower and west of the remaining
deterministic and ensemble means. Late Tuesday into Wednesday, a
second, compact mid-level closed low is forecast to sweep across
New England atop a cold and post-frontal environment. There are
only minor timing and latitude differences in place with this
second shortwave so a general model blend will work overall for
the Northeast.
...Shortwave energy shearing across the Southern Plains Monday
night and Tuesday...
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Preference: General model blend
Confidence: Average
...19Z update...
No significant changes were noted with the 12Z ECMWF/UKMET/CMC
compared to their 00Z cycles for this system.
...previous discussion follows...
A subtle shortwave will move through portions of the Desert
Southwest today before crossing into the southern Plains and lower
Mississippi Valley early next week. Regarding mass fields, only
minor differences are noted with the latest model guidance. The
differences in precipitation are driven more by mesoscale factors
which fall outside the scope of this discussion.
...Upper trough/closed low along the Northwest Coast through
Wednesday...
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Preference: 12Z NAM/GFS/ECMWF blend
Confidence: Average
...19Z update...
No significant changes were noted with the 12Z ECMWF/CMC compared
to their 00Z cycles for this system but the 12Z UKMET trended
slightly toward the CMC. The ensemble means show better support
for a 12Z NAM/GFS/ECMWF blend.
...previous discussion follows...
The models are in fair agreement with the mean closed mid-level
low position off of the Pacific Northwest through Wednesday, and
as the shortwave moves inland toward the end of the week. Only the
00Z CMC differed significantly enough with the center of the
closed low being displaced farther offshore compared to the good
agreement noted in the remaining deterministic and ensemble
guidance.
...Upper low closing off over western Canada on Tuesday before
moving east through the Canadian Prairie Wednesday-Thursday...
...Surface cyclone moving trough the north-central U.S. Wednesday
night...
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Preference: non 12Z UKMET blend
Confidence: Average
...19Z update...
Regarding the lead shortwave, no large changes were noted with the
12Z ECMWF/UKMET/CMC but the 12Z ECMWF strengthened slightly toward
the remaining consensus.
The 12Z UKMET remains separated with the trailing shortwave across
southwestern Canada although it did nudge in the direction of the
remaining consensus in the 12Z models. There are only minor timing
differences with the shortwave outside of the 12Z UKMET, with the
12Z NAM slowest and more weight preferred toward the 12Z
GFS/ECMWF/CMC.
...previous discussion follows...
A combination of shortwaves will impact the north-central U.S.
from Wednesday into Thursday. The first will be relatively weak,
emanating from ID/MT/WY Tuesday night. The 00Z ECMWF is weaker
with this feature compared to the remaining model consensus and is
noted with the 00Z ECMWF surface reflection differing from the
remaining guidance. The 00Z UKMET is similar to the remaining
guidance with this feature but differs up north with its handling
of a shortwave moving across southwestern Canada. With a more
elongated shortwave noted in the 00Z UKMET, a piece of shortwave
energy is left behind near northwestern Montana compared to the
remaining consensus. Overall, decent agreement is in place with
the 12Z NAM, 12Z GFS and 00Z CMC overall for the north-central
U.S., but aspects of the 00Z ECMWF and 00Z UKMET may be usable at
times.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Otto