Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
132 PM EST Mon Mar 04 2019
Valid Mar 04/1200 UTC thru Mar 08/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation Including Preference and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...Deep trough over the Great Lakes/Northeast...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average
There is generally good large scale agreement with the models on
the deep trough that will be evolving over the Great Lakes region
and adjacent areas of the Northeast going through midweek. A
couple of shortwave impulses will be digging through the base of
the trough with impacts on the Midwest/OH Valley, but the guidance
shows only very modest differences with these features. A general
model blend will be preferred as a result.
...Deep closed low center near 32N 143W...
...Arriving across CA by Wed...
...Shearing downstream across the central Plains on Thurs...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend...through 60 hours
Non-GFS blend after 60 hours
Confidence: Above average
The models take a deep closed low near 32N 143W and eject it
progressive east into CA by Wednesday as an open shortwave trough
as the energy gets caught up underneath larger scale and stronger
height falls dropping south offshore the Pacific Northwest. The
guidance shows good agreement as the energy crosses CA on
Wednesday, but then on Thursday as the energy ejects out across
the central Plains, the 12Z GFS becomes a stronger outlier
solution which helps to bring a wave of low pressure a bit farther
northeast up across southeast KS and southwest MO along with a
downstream warm front that is farther north across the mid-MS
Valley. The remaining guidance agrees with a relatively flatter
evolution which makes more sense considering the downstream
confluent flow aloft over the Midwest that this energy will be
encountering. Will recommend a general model blend as the energy
initially advances inland, but after about 60 hours, a non-GFS
blend will be preferred.
...Deep closed low near the Pacific Northwest...
...Undercutting shortwave trough approaching CA on Thurs...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend
Confidence: Above average
A rather deep closed low will be positioned near the Pacific
Northwest for the next few days as shortwave energy drops down
around the west side of the height falls and undercuts the base of
the trough with a trajectory toward the West Coast and an emphasis
on CA. Differences with the closed low itself are quite modest
through the period, and have clustered together a bit better this
cycle. Regarding the shortwave undercutting the closed low and
approaching CA by Thursday, the 12Z NAM becomes a bit of a
stronger outlier compared to the global models. Will prefer a
non-NAM blend at this point considering the better overall
clustering seen now with the global models.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Orrison