Prognostic Meteorological Discussion
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000
FXUS10 KWNH 261847
PMDHMD

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
246 PM EDT Sat May 26 2018

Valid May 26/1200 UTC thru May 30/0000 UTC

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

12Z model evaluation including final preferences and confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

***Subtropical Storm Alberto***
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: See NHC Forecast
Closest Guidance: 00z ECMWF/CMC blend

The majority of the guidance has come into better agreement on the
track and intensity of Alberto, which is currently near western
Cuba early Saturday afternoon.  The past few runs of the UKMET,
including today`s 12Z run, are east of the model consensus and not
supported by the ensemble mean guidance.  The 12Z ECMWF has
trended to the east of the 00Z run through early Monday.  By
Monday evening, the NAM and GFS are quickest with a landfall over
the Alabama coast, with the CMC and ECMWF closer to the slower
ensemble means.  The official NHC track and forecast has
additional information pertaining to this storm.


***Disturbances crossing the Great Lakes and Northeast U.S.***
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend through 18Z Monday, then non-NAM
consensus
Confidence: Above average

The model guidance is in decent overall agreement regarding a
series of shortwave perturbations in the northern stream flow
across the Great Lakes and the Northeast U.S. through early
Tuesday.  The NAM begins to differ some by midday Monday with a
stronger ridge over the Midwest and a more amplified and faster
trough approaching northern New England Monday night.


***Western U.S. closed low and surface cold front***
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

A large and slow moving upper low is expected over much of the
Intermountain West through the holiday weekend before evolving
into an open wave by early Tuesday.  The models continue to be in
good agreement with the evolution of the closed low over the Great
Basin Sunday into Monday.  Only modest differences become apparent
by Tuesday, with the GFS slightly more amplified and CMC slightly
more progressive, but they don`t deviate enough to discount from
the preferences.  A general model blend should suffice with above
average confidence on the synoptic scale.


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

Hamrick



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