Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
118 PM EDT Sat Mar 30 2019

Valid Mar 30/1200 UTC thru Apr 03/0000 UTC

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

12Z NAM/GFS Evaluation With Preliminary Preferences and Confidence
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...Cold front moving through the eastern third of the nation
through Sunday...
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Preference: General model blend
Confidence: Above average

Only minor differences remain with this system. Trends in timing
have been converging upon the steady ECWMF mean, with the latest
guidance showing reasonable agreement. Therefore, a general model
blend is preferred with this system.


...Four Corners to Southern Plains trough/closed low...
...Reaching the Gulf Coast/Southeast by Mon/Tues...
...Cyclogenesis near the Southeast Coast by Tues...
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Preference: 30% 12Z GFS/70% 00Z ECMWF
Confidence: Average

The 12Z GFS appears to be too fast as the mid-level shortwave
reaches Texas with a strong remaining consensus slower with the
wave. The 00Z CMC/UKMET are slower but the 12Z NAM ends up on the
slowest side of the ensemble envelope and a bit stronger as the
shortwave moves into the southeastern U.S. Recent trends with the
GFS and GEFS have been to slow down with shortwaves progressing
from west to east in this flow pattern and the 12Z GFS lies on the
faster edge of the guidance. Therefore, given some differences
aloft with the 00Z UKMET/CMC earlier with the handling of the
shortwave, the 00Z ECMWF, when blended with the 12Z GFS slightly,
is preferred for this system.


...Trough/Low approaching the West Coast on Mon...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Near the 12Z GFS
Confidence: Average

Reasonably good agreement exists with this system until late
Monday into Tuesday when the amplitude of the upper trough shows
differently in the models. The 00Z UKMET/CMC are near outliers
with their handling of the mid-level energy resulting in a closed
low off of Vancouver Island. The 12Z NAM is deeper with the trough
amplitude out West while the 00Z ECMWF is a bit flatter. The 12Z
GFS appears to be a good middle ground for this system.


...Upper trough over the Northern Plains/Midwest Tues...
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Preference: 12Z NAM/00Z ECMWF blend
Confidence: Average

The 12Z GFS is faster, noted with the 850-700 mb timing of the
wave, with the 00Z ECMWF and 12Z NAM showing good agreement from
the latest ensemble guidance.


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

Otto