Prognostic Meteorological Discussion
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000
FXUS10 KWNH 241834
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
133 PM EST SAT JAN 24 2015

VALID JAN 24/1200 UTC THRU JAN 28/0000 UTC

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

12Z MODEL EVALUATION WITH PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


SHORTWAVE NEAR THE PACIFIC NORTHWEST TUE NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GUIDANCE SHOWS REASONABLE AGREEMENT WITH THIS SYSTEM.


CLOSED LOW MOVING INTO THE WEST LATE MONDAY/TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z NAM IS THE STRONGEST WITH THIS SYSTEM ALOFT, WHICH IS ITS
TYPICAL BIAS.  PREFER A NON-NAM COMPROMISE WITH THIS SLOW-MOVING
AND RELATIVELY LARGE SYSTEM WITH ABOVE AVERAGE CONFIDENCE.


CLIPPER SYSTEM MOVING BY THE GREAT LAKES MON/TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GUIDANCE HAS OVERALL TRENDED EAST WITH THIS SYSTEM SINCE THIS
TIME YESTERDAY, MOSTLY DUE TO A STRONGER/BROADER RIDGE ACROSS THE
WEST, AND IS STRONGER AT THE SURFACE DESPITE ITS WEAK APPEARANCE
ALOFT.  PREFER A GENERAL MODEL COMPROMISE WITH THIS SYSTEM TO DEAL
WITH LINGERING DETAIL ISSUES.


CLIPPER-TYPE SYSTEM EVOLVING INTO A NOR`EASTER MON/TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: UKMET/CANADIAN COMPROMISE
CONFIDENCE: BELOW AVERAGE

THERE IS UNCERTAINTY WITH THIS SYSTEM, WITH SOME OF IT INTRODUCED
BY AN UPSTREAM SHORTWAVE STREAKING NEAR THE GREAT LAKES AND SOME
INTRODUCED BY ITS BURGEONING SIZE OF THE OVERALL SYSTEM AS IT
APPROACHES THE NORTHEAST/NEW ENGLAND.  THE 12Z GFS IS THE
STRONGEST/MOST CONSOLIDATED ALOFT.  THE 12Z ECMWF USES WHAT
APPEARS TO BE A CONVECTIVE FEEDBACK BULL`S EYE AT 60-66
HOURS/MONDAY NIGHT TO DRAG ITS SURFACE LOW DUE NORTH ONCE IT
EMERGES OFF CAPE HATTERAS, WHICH LOOKS UNREALISTIC.  WITH AT LEAST
TWO NOTABLE SHORTWAVES MERGING TO CREATE THIS LARGE SYSTEM, IT
COULD TAKE A WHILE TO CONSOLIDATE ALOFT, IMPLYING THE GFS IS
PROBABLY TOO DEEP ALOFT.  THE TREND IN THE ECMWF IS TOWARDS A MORE
SOUTHERLY SYSTEM, WHILE THE ECMWF/GFS/UKMET HAVE TRENDED STRONGER
ALOFT OVER THEIR PAST DAY OR SO OF RUNS, WHICH HAS FORCED A
WESTWARD TREND AT THE SURFACE.  WITH THE STRENGTHENING TREND
ALOFT/WESTERLY SURFACE CYCLONE TRACK TREND, THE 00Z GLOBAL
ENSEMBLE GUIDANCE APPEARS TO HAVE LITTLE UTILITY TODAY.  A
COMPROMISE OF THE 12Z GFS/12Z ECMWF, CLOSE TO THE 12Z UKMET/12Z
CANADIAN, IS PREFERRED WITH BELOW AVERAGE CONFIDENCE DUE TO THE
LARGE DAY-T0-DAY CHANGES SEEN IN THE DETERMINISTIC GUIDANCE.


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

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

ROTH
$$




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