Prognostic Meteorological Discussion
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000
FXUS10 KWNH 260648
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 AM EST WED NOV 26 2014

VALID NOV 26/0000 UTC THRU NOV 29/1200 UTC

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

00Z NAM/GFS EVALUATION INCLUDING THE UKMET/CANADIAN/ECMWF AND
PREFERENCES

...LOW PRESSURE OVER THE NORTHERN PLAINS...

THE MODELS HAVE COME INTO GOOD AGREEMENT INCLUDING WITH THE NEW
ECMWF TO SUGGEST EQUAL USE OF THE GUIDANCE.

...LOW PRESSURE FORMING ALONG THE EAST COAST...

PREFERENCE: HALFWAY BETWEEN THE NAM AND GFS...ESSENTIALLY A MODEL
CONSENSUS
CONFIDENCE: AVERAGE

OTHER THAN THE CANADIAN...00Z GUIDANCE IS WELL CLUSTERED...WITH
TRENDS SUPPORTING A SLIGHT SLOWING AND WESTWARD SHIFT TO THE
PREVIOUS FORECAST...BUT ONLY SO MUCH AS SO AS TO REPRESENT A
SLIGHT CHANGE...AS THE MODELS CONTINUE TO SHOW ENOUGH SPREAD AND
RUN-TO-RUN VARIABILITY TO WARRANT A FOCUS ON A MODEL CONSENSUS AND
FORECAST CONTINUITY.  AN EQUAL BLEND OF THE NAM AND GFS SEEM TO
BEST REPRESENT THIS CONSENSUS AS IT IS SIMPLE.  HOWEVER...OTHER
COMBINATIONS WILL ALSO WORK.  TWO SOLUTIONS FROM 00Z THAT ARE
FARTHEST FROM THE CONSENSUS INCLUDE THE CANADIAN WHICH PRESENTLY
LIES NEAR THE NORTH AND NORTHEASTERN SIDES OF THE GUIDANCE...AND
THE ECMWF WHICH HAS MADE ONE OF THE LARGER RUN-TO-RUN CHANGES BY
DRIFTING TOWARD THE WESTERN EDGE OF THE GUIDANCE FROM 00-12Z
THU...INCLUDING WITH RESPECT TO ITS OWN ENSEMBLE MEMBERS.  IF ONE
WERE TO USE THE ECMWF...ONE RECOMMENDATION IS TO BLEND IT WITH THE
PREVIOUS RUN OR OTHER 00Z GUIDANCE TO SMOOTH ITS MORE WESTERN
ORIENTED SOLUTION THAT PRESENTLY HAS VERY FEW SUPPORTING
SOLUTIONS.

...SHORTWAVE TROUGH INFLUENCING THE PACIFIC NORTHWEST AND NORTHERN
ROCKIES THU/FRI...

PREFERENCE: BEFORE 12Z FRI...NAM OR ECMWF
             AFTER 12Z FRI...ECMWF
CONFIDENCE: ABOVE AVERAGE

THE NAM AND ECMWF SHOW STRONG AGREEMENT WITH EACH OTHER AND
CLUSTER WELL WITH THE REMAINING SOLUTIONS AND THE ENSEMBLE MEANS
EXCEPT THE GFS WHICH IS NEARLY A FAST OUTLIER WITH THE NORTHERN
STREAM ACROSS CANADA RESULTING IN A VERY DIFFERENT FRONTAL
DEPICTION OVER THE DAKOTAS BY EARLY SATURDAY.  AFTER 12Z
FRIDAY...THE GFS REMAINS TOO FAST OVER CANADA AND THE NAM TOO
PROGRESSIVE WITH THE SOUTHERN STREAM ENTERING THE WEST COAST.
MEANWHILE...THE ECMWF LIES NEAR THE MIDDLE OF THE SOLUTION
ENVELOPE AND HAS THE STRONGEST SUPPORT FROM THE ENSEMBLE MEANS.
THEREFORE...RECOMMEND THE ECMWF FROM FRIDAY ONWARD.

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

JAMES

$$





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