Prognostic Meteorological Discussion
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FXUS10 KWNH 160406
Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1205 AM EDT Fri Mar 16 2018

Valid Mar 16/0000 UTC thru Mar 19/1200 UTC

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

00Z Model Evaluation including model preferences and forecast

...Deep cyclone over the Northeast U.S. and eastern Canada with
digging shortwaves from Hudson Bay region wrapping through south
side of the cyclone with gradual shift to the east By Sunday...
Preference: Non-CMC blend
Confidence: Above Average

Deep, occluded currently centered near Ile d`Anticosti will
continue to fill and wobble northward as a weak shortwave moves
through the base of the broader cyclone across the Mid-Atlantic
today.  Eventually, a strong pool of cold air and northwesterly
flow over eastern Nunavut plunges south with a strong shortwave
eventually replacing the center/focus of the larger scale vortex
over SE Canada (clipping northern New England) Sunday.  Model
guidance as come into stronger agreement in timing/shape of this
upstream stronger wave with exception of the 12z CMC.  The 12z CMC
while better than prior runs remains a less intense with higher
heights and is slightly displaced to the north and west to the
otherwise very tight clustering presented by the 00z GFS/NAM and
12z ECMWF/UKMET and their counterpart ensemble suite.   As such
will favor a non-CMC blend at Above average confidence.

...Negative-tilt shortwave ejecting into the Central Plains by
Friday with associated strong surface cyclogenesis...Deamplifying
through Ohio Valley and Carolinas this weekend...
Preference: 00z GFS and 12z ECMWF/UKMET blend
Confidence: Slightly Above Average

Goes-W WV depicts a strong shortwave at the base of the larger
scale western trof beginning to take more of a negative-tilt
orientation as it tracks through the four-corners currently.  A
lee cyclone is beginning to rapidly deepen across SE CO/SW KS at
this moment as well.  Guidance continues to evolve this wave into
a compact banded stacked system under the upper-level diffluent
pattern aloft across KS by midday today.  Eventually, riding into
the larger scale ridge over the MS River Valley, the system
quickly breaks down and shears into the westerly flow.  Guidance
has been trending toward a common solution with a lead weak piece
of energy leading the main core through the Ohio Valley and
eventually Mid-Atlantic/Carolinas Sat.  The NAM which had been a
faster solution has slowed with the 00z run, however, typical
negative bias of the NAM shows a more robust vorticity center with
the remaining inner core/upstream wave through the Ohio Valley
Sat.  This leads it to delay even further than the slowest other
solutions (12z CMC).  The 00z GFS continues to converge with the
12z UKMET/ECMWF solutions with respect to the wave elongation as
well as the depth/timing and placement of the surface wave; enough
so to continue a 00z GFS and 12z ECMWF/UKMET blend.  Confidence
remains slightly above average as well in this blend preference.

...Northern peripheral shortwave across S Canadian Rockies that
rotates to Vancouver Island late Saturday and then consolidates
and stalls just off WA/OR coast Sun/Mon...
Preference: 00z NAM/12z ECMWF blend
Confidence: Average

Goes-WV and Radar Mosaic depict center of elongating shortwave
feature across S Alberta at this time.  Guidance is fairly
confident in a retrograde across central BC over the next day or
so around the northern periphery of the larger scale vortex.  By
late Sat into Sunday, the wave will consolidate again near/along
the western coast of Vancouver island and settle south toward the
WA coast.  The 12z CMC is a bit more aggressive in drawing the
wave south with stronger ridging developing to the north.

The model spread begins to increase as the main vortex breaks down
as well as the approach of a stronger/more compact closed low from
the Central Pacific advances east; and by midday Sun the system
either begins to shift south or begins to elongate E-W in between
the two systems.  The 12z ECMWF/00z NAM are a bit more progressive
south while the GFS and the UKMET hang back and stretch.
Ensembles support there respective operational runs, however
ensembles supporting a slightly slower central Pacific wave would
shift favor slightly to the progressive solutions.  As such an 12z
ECMWF and 00z NAM blend is favored slightly over a general model
blend; confidence is average in this preference over the general
model blend.

...Core of large scale deep layered cyclone off OR coast enters
CA/NV Sat/early Sunday before swinging strong height-falls into
negative tilt trof through central Rockies with associated strong
lee sfc cyclone early Mon in Southern Plains...
Preference: General Model Blend
Confidence: Above average

Goes-W WV depicts a deep layered cyclone centered off the OR coast
at this time with an upstream shortwave near the Queen Charlotte
Islands.  This pair will go through a binary interaction...with
the main center slowly drifting across N CA into NV by Sat with
the upstream s/w descending in latitude paralleling the coast.  As
the main center translates east into the Great Basin, it weakens
slowly deferring to the strengthening s/w rounding its base Sun
into the four corners region. The wave then goes negative tilt
early Monday and spurs strong lee cyclogenesis in SE CO shifting
to OK by the end of the period.  The 00z trended ever so slightly
slower and while still a tad stronger in depth through the
evolution joins the remarkably strong clustering in timing and
evolution of the system anchored by the 12z ECMWF/UKMET and CMC as
well as the 00z GFS and its prior run(s).    While the NAM is
agreeable in mass fields there are issues with respect to the
placement of convective initiation and QPF (please refer to QPFPFD
for additional details).  Still all considering above average
confidence could be afforded in a general model blend.

Model trends at
500 mb forecasts at


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