Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1113 AM EST Tue Feb 25 2020
Valid Feb 25/1200 UTC thru Feb 29/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation Including Preliminary Preferences
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...Eastern Half of North America...
Preference: Blend of 12Z NAM with 00Z ECMWF/UKMET
Gradual phasing of northern and southern streams will lead to
mature cyclone development over the northeastern U.S. and
southeast Canada by Thursday. The then-mature, full latitude
trough will occupy the eastern U.S. for another day or two.
The models are all generally agreeable aloft. The main deviant
model, as noted overnight, was the 00Z Canadian with its more
fully developed coastal low. Most solutions do have a semblance of
a double-barrel low, with the primary tracking into Quebec, and
another low attempting to form along the coast from Maine to the
Canadian Maritimes. But the Canadian solution is more bullish
along the coast.
In the 12Z cycle what stands out is a sudden and stark deepening
trend in the GFS, which takes the primary surface low down to 983
mb at 28/00z, a time when the GEFS mean is only 989 mb, and other
global models are squarely in that 988 to 992 range. The GFS gets
there by means of a sharper, more energetic wave emerging from the
southern Rockies this evening. Although 500-250 mb observed winds
were impressive at Albuquerque and Amarillo this morning, there
does not appear to be anything especially impressive about this
wave, and the fact that the NAM - whose bias is strong and deep -
does not support this trend, perhaps speaks volumes. We therefore
prefer the NAM along with the better solutions from overnight, the
ECMWF and UKMET.
...Western U.S...
Preference: Blend of the 00Z ECMWF/Canadian
A minor shortwave trough will scoot through the northwest U.S.
today and tomorrow. Then expect a building shortwave ridge in
advance of what looks like a Day 4 system to arrive Friday night /
Saturday. The NCEP solutions have been noticeably much faster than
the other global guidance in bringing the next wave toward the
coast on Friday. On the other hand, the 00Z UKMET set the slow and
strong side of the envelope. Wave spacing across the Pacific
suggest a trough about in the position of the ECMWF and Canadian
solutions as of 29/00Z, the end of the short range period. This is
our preference, and the GFS did trend a bit toward this preference
while still looking a tad fast.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Burke