Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
308 PM EST Wed Feb 19 2020
Valid Feb 19/1200 UTC thru Feb 23/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation with Latest Preferences and Confidence
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Overall Pattern Across the CONUS
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Preference: General model blend through 21.00Z; then
GFS/ECMWF/UKMET blend
Confidence: Average to slightly above average
20Z update: With the rest of the 12Z guidance now available, there
remains fairly good consensus through about 21.00Z to go with a
general model blend across the CONUS. Differences then begin along
both coasts. First, for the coastal storm off NC, the NAM remains
the outlier with its low position off NC by 21.00Z. For Day 3
across the Southwest U.S., the 12Z CMC is considerably faster with
the closed low tracking toward the Four Corners region, even ahead
of the typical fast GFS. It was considered less useful for that
area. As such, the model preference was adjusted to go with a
GFS/ECMWF/UKMET blend beyond 21.00Z.
The synoptic pattern at the beginning of the forecast period is
expected to feature mostly zonal flow across the central/eastern
U.S. while a western ridge remains anchored through much of the
west coast and Pacific Northwest. A shortwave trough swings
through the Great Lakes region Thursday, reaching the Atlantic
toward Friday while out west, a closed low develops off the
southern California coast, creating a split flow through the
CONUS. The closed ULL reaches the Four Corners region by the end
of the forecast period.
Low pressure is expected to form off the North Carolina coast late
Thursday. Model guidance has trended tighter and there is somewhat
less spread in the low positions over the last 4 model cycles. The
NAM remains the bullish solution, with a low closer to the coast,
while the ECMWF deterministic is still further offshore. The 12Z
GFS lies in between, closer now toward the ECMWF solution.
Overall, the NAM is still considered a bit of an outlier and was
not preferred for day 2/3.
For the closed low out west, there is reasonable consensus and
agreement through most of the period. Toward the end of day 3, the
GFS becomes a bit fast with its progression over the Four Corners
but the spread is still fairly minimal such that a general model
blend would suffice there.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Taylor