Prognostic Meteorological Discussion
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000
FXUS10 KWNH 250637
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
136 AM EST SUN JAN 25 2015

VALID JAN 25/0000 UTC THRU JAN 28/1200 UTC

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

00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


SHORTWAVE INTO THE PACIFIC NORTHWEST ON TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

WITH SLOWER ADJUSTMENTS MADE BY THE 00Z CMC...THE GUIDANCE NOW
SHOWS REASONABLE AGREEMENT WITH THIS SYSTEM.


CLOSED LOW MOVING INTO THE WEST EARLY TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS SHOW ENOUGH AGREEMENT HERE SUCH THAT A GENERAL MODEL
COMPROMISE CAN BE PREFERRED.


CLIPPER SYSTEM MOVING BY THE GREAT LAKES MON AND MON NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS / 00Z UKMET BLEND
CONFIDENCE: AVERAGE

MUCH OF THE GUIDANCE HAS TRENDED EAST OVERALL WITH THIS SYSTEM
SINCE YESTERDAY...BUT THE 12Z ECMWF/ECMWF MEAN ARE DIFFERENT FROM
THE REMAINING MODEL CLUSERTERING IN BEING QUICKER/SOUTH WITH THE
CORRESPONDING VORTICITY MAX NEAR 500 MB. THE 00Z ECMWF ADJUSTED
TOWARD THE GFS BUT THE 00Z UKMET IS A BETTER FIT IN THE BLEND THAN
THE 00Z ECMWF...SO A 00Z GFS/UKMET BLEND IS PREFERRED HERE WHICH
REPRESENTS THE MIDDLE OF THE LATEST DETERMINISTIC/ENSEMBLE SPREAD.


CLIPPER-TYPE SYSTEM CROSSING THE EAST COAST SUN NIGHT AND
STRENGTHENING COASTAL LOW OFF OF NEW ENGLAND ON TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 00Z GFS / 00Z ECMWF THROUGH 12Z/27
            BLEND OF 00Z GFS / 12Z EC MEAN BETWEEN 12Z/27-12Z/28
CONFIDENCE: BELOW AVERAGE

THERE HAS BEEN A DRAMATIC SHIFT IN THE GUIDANCE SINCE YESTERDAY TO
BE CLOSER TO THE NORTHEAST COAST TUE MORNING REGARDING A SURFACE
LOW...PARTIALLY DUE TO A STRONGER RIDGE OVER THE SRN HIGH PLAINS
AND DOWNSTREAM UPPER TROUGH SHARPER AND WEST OF PREVIOUS RUNS.
TAKING A LOOK AT 12Z/27...F060 HRS...THE LATEST ENSEMBLE
DISTRIBUTION OF SURFACE LOWS FROM 12Z/24 SHOWS THE ECMWF MEMBERS
STRONGLY CLUSTERED TO THE WEST OF THE RELATIVELY WELL CLUSTERED
GEFS WHILE CMC MEMBERS ARE SCATTERED ACROSS BOTH REGIONS. SUBTLE
RUN TO RUN CHANGES TRANSLATE INTO SIGNIFICANT IMPACT DIFFERENCES
ACROSS NEW ENGLAND.

THE CURRENT THINKING IS CLOSE TO WPC CONTINUITY BUT ADJUSTED FOR
THE LATEST GUIDANCE WHICH SHOWS THE 00Z GFS AND 00Z ECMWF CLOSE TO
WHAT IS EXPECTED TO OCCUR UNTIL ROUGHLY 12Z/27...AT WHICH POINT
THE 00Z ECMWF STARTS TO STRAY FROM THE PACK IN HOLDING THE SURFACE
LOW MORE SOUTH WHILE BETTER ENSEMBLE CLUSTERING AND THE LATEST
MEANS LIE TO THE NORTH. THIS PREFERENCE REFLECTS MODEL TRENDS AND
IS AWAY FROM THE EDGES OF THE ENSEMBLE CLUSTERING. HOWEVER...POOR
RUN TO RUN CONTINUITY AND ABOVE AVERAGE ENSEMBLE SPREAD LOWERS
CONFIDENCE FOR THIS FORECAST.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

$$




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