Prognostic Meteorological Discussion
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000
FXUS10 KWNH 291642
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1241 PM EDT MON SEP 29 2014

VALID SEP 29/1200 UTC THRU OCT 03/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

==================================================
12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES
==================================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==================================================

...CYCLOGENESIS IN THE NORTHERN PLAINS...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS

AT THE LEADING EDGE OF A LARGE SCALE TROUGH...A SMALLER SCALE
CYCLONE WILL EVOLVE OVER THE NORTHERN PLAINS BEFORE LIFTING INTO
CANADA. MODELS SHOW STRONG AGREEMENT AS TO THE DETAILS.


...SHORTWAVES DIGGING THROUGH THE ROCKIES AND PLAINS WED/THU...

PREFERENCE: 12Z GFS

THE FORECAST HERE IS MADE PARTICULARLY CHALLENGING BY EXISTENCE OF
A SPLIT STREAM WITHIN NORTHWESTERLY FLOW AND ABOUT A 200 MILE
EAST-WEST SEPARATION BETWEEN THE GEFS MEAN AND ECMWF ENSEMBLE MEAN
ALONG THE LARGER SCALE TROUGH AXIS BY THURSDAY. THE PREVIOUS SHIFT
NOTED THAT THE OPERATIONAL ECMWF...BEING EVEN MORE PROGRESSIVE
THAN ITS ENSEMBLE MEAN...WAS THE WEAKEST AND MOST PROGRESSIVE
SOLUTION THAT CAN BE FOUND. MEANWHILE...THE GFS AND NAM HAVE SHOWN
CONSISTENCY WITH ONE ANOTHER AND RUN TO RUN CONSISTENCY IN THE
29/00Z TO 29/06Z AND 29/12Z RUNS. THEY ARE SUPPORTED BY THE 06Z
GEFS MEAN AND THE NAEFS MEAN WHICH INCORPORATES THE CANADIAN
MODELING CENTER ENSEMBLE. THIS CLUSTER OF MODELS HAS SHOWN A
DISTINCT TREND TOWARD THE SLOWER AND MORE AMPLIFIED SOLUTION IN
THE SOUTHERN PLAINS...AND ALSO A BREAKDOWN OF SHORTWAVE RIDGING
ALONG THE WEST COAST OF BRITISH COLUMBIA THURSDAY. ALTHOUGH
PERHAPS NOT DIRECTLY RELATED...SEEING DISTINCT TRENDS IN TWO KEY
AREAS OF THE MAP GIVES US INCREASED CONFIDENCE THAT THE MORE
RECENT GUIDANCE IS IDENTIFYING TRENDS THAT WILL STICK. THE NAM
BEING A BIT DEEPER/STRONGER IN THE PLAINS...WE RECOMMEND THE
SOMEWHAT MORE CONSERVATIVE 12Z GFS.


...SHORTWAVE TROUGH DIGGING INTO THE MID-ATLANTIC/SOUTHERN NEW
ENGLAND...

PREFERENCE: 00Z ECMWF

HERE MODEL DIFFERENCES ARE MINOR. THERE ARE NO OUTLIERS...AND ONE
COULD RECOMMEND A BLEND OF THE OPERATIONAL MODELS. WE HAVE A
SLIGHT PREFERENCE TOWARD THE ECMWF AND ECMWF ENSEMBLE MEAN...WHICH
MAINTAIN A CLOSED LOW FOR LONGER DURATION AND DRIFTING AT A
SLIGHTLY SLOWER PACE. THIS WOULD SEEM FAVORED BY ITS POSITION
WITHIN A LARGER SCALE SHORTWAVE RIDGE.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BURKE
$$




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