Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
247 AM EDT Thu Mar 21 2019
Valid Mar 21/0000 UTC thru Mar 24/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
00Z Model Evaluation Including Preferences and Confidence
...Trough(s) and Developing Low in the East...
Preference: General model blend (weight to ECMWF/GFS/UKMET)
Confidence: Slightly above average
07z update: With the rest of the 00z guidance now available, the
agreement has improved and now the CMC mirrors the rest of the
guidance very well. As such, a general model blend can be used for
the east coast system mass fields.
Two pieces of mid/upper level energy rotating through the Great
Lakes and Mid-Atlantic regions will phase in the next 24-48 hours
over the Northeast US, eventually closing off Friday night off the
Northeast US coast. A surface low, currently near the SC/NC
border, will track up the East Coast, deepening as it moves toward
the Gulf of Maine. Mass fields between the various deterministic
models are in much better agreement compared to the past few
cycles, particularly in the first 24-36 hours. The mid/upper level
pattern is fairly similar across the board, while at the surface,
there remains a few differences in the track/position. The 12z CMC
is further east compared to the model consensus, while the rest of
the guidance is nearly identical in track and magnitude. As such,
will lean on a non-CMC blend for this system with the heaviest
weight given to the ECMWF/GFS/UKMET.
...Remainder of the CONUS...
Preference: General model blend
07z update: The rest of the 00z guidance looks reasonable for the
western/central US through the period. The preference for a
general model blend continues.
The strong elongated ridge in place across the Plains will
continue early in the forecast period while a slightly negatively
titled trough weakens and splits as it moves onshore the west
coast. The main energy source will pinch off toward the Southwest
US, eventually closing off over Utah by Friday. Through then,
model agreement is above average and a general model blend can be
used for the mass fields.
Some of that energy eventually makes it way toward the central
Plains by Saturday where there are some disagreements in timing
and location. The ECMWF is further south with the mid/upper low
position compared to the CMC which is on the northern edge of the
model consensus. The latest (00z) GFS/NAM split the difference but
appear to be slightly faster as well. But overall, the differences
are not substantial and a general model blend probably would yield
a reasonable result for 3 days out.
Weak troughing will remain in place across northern California
into the Pacific Northwest for the end of the forecast period.
There are differences on how strong (south) the trough influence
is, but again, model differences are not significant enough to
lean/prefer one solution over another.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml