Prognostic Meteorological Discussion
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000
FXUS10 KWNH 251829
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
128 PM EST SUN JAN 25 2015

VALID JAN 25/1200 UTC THRU JAN 29/0000 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.


MERGING SHORTWAVE MOVING INTO THE PLAINS WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE DETERMINISTIC GUIDANCE SHOWS MUCH LESS SPREAD THAN THE 00Z
GLOBAL ENSEMBLE SPREAD WITH THIS SYSTEM.  DUE TO THIS, PREFER A
COMPROMISE OF THE 12Z ECMWF/12Z GFS, WITH THE LINGERING SPREAD IN
THE GUIDANCE KEEPING CONFIDENCE AVERAGE.


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

THE GUIDANCE IS IN GOOD AGREEMENT HERE.


CLIPPER SYSTEM MOVING BY WISCONSIN MONDAY/TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE GUIDANCE SHOWS DECREASING SPREAD HERE, WITH THE 12Z GFS/12Z
ECMWF SPLITTING THE DIFFERENCE IN THE DETERMINISTIC AND GLOBAL
ENSEMBLE SPREAD.  A 12Z GFS/12Z ECMWF COMPROMISE IS PREFERRED WITH
AVERAGE CONFIDENCE CONSIDERING ITS QUICK PROGRESSION AND LINGERING
MODEL SPREAD.


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

THERE REMAIN SOME SLIGHT EAST-WEST AND SLIGHT PROGRESSION ISSUES
WITH THIS SYSTEM WHICH PLAY HAVOC WITH THE PRECIPITATION/WINTER
WEATHER FORECAST.  THE 12Z ECMWF, 12Z NAM, AND 12Z GFS HAVE WHAT
APPEAR TO BE CONVECTIVE FEEDBACK BULL`S EYES CONTAMINATING THEIR
SOLUTIONS -- THE 12Z UKMET/12Z CANADIAN ALSO SHOWS SIGNS OF GRID
SCALE FEEDBACK.  THE NAM/ECMWF BULL`S EYES OVER THE GULF STREAM
OFFSHORE THE EAST COAST APPEAR TO CAUSE AN EASTWARD SHIFT IN THEIR
12Z SOLUTION AT THE SURFACE AND ALOFT ON (DAY 2 ON THE NAM AND DAY
3 ON THE ECMWF).  THE GFS`S BULL`S EYE/QPF BOMB DRAGS ITS BOUNDARY
LAYER WIND CIRCULATION ACROSS CAPE COD AND THE ISLANDS ON ITS 12Z
RUN, MORE TO THE WEST OF THE OTHER GUIDANCE DESPITE ITS SURFACE
PRESSURE PATTERN.  THERE IS A CHANCE OF SOME WOBBLING/LOOPING OF
THE CENTER OF THE SURFACE LOW DUE TO AN INVADING SHORTWAVE
ROUNDING ITS SOUTHWEST SIDE ON TUESDAY, WHICH WOULD LEAD TO AN
UNEVEN FORWARD PROGRESSION.  THE 00Z GLOBAL ENSEMBLE GUIDANCE
ENVELOPE OF SOLUTIONS MIRRORS THE ENVELOPE OF DETERMINISTIC
SOLUTIONS AMONGST THE GFS, NAM, ECMWF, CANADIAN, AND UKMET.  THERE
IS NO OVERARCHING TREND SINCE THIS TIME YESTERDAY TOWARDS A
QUICKER OR SLOWER SOLUTION, THOUGH THE NAM/GFS/ECMWF/UKMET HAVE
TRENDED WESTWARD -- IN THE DIRECTION OF THE 12Z GFS.  THE
OCCASIONALLY SLOW/PLODDING 09Z SREF MEAN LIES IN THE MIDDLE OF THE
DETERMINISTIC MODEL SPREAD, QUICKER THAN THE 12Z NAM/12Z ECMWF
SOLUTIONS.  SINCE NO SOLUTION CAN BE COMPLETELY DISCOUNTED WHEN
USING THE SURFACE PRESSURE FIELD, 700 HPA HEIGHT FIELD, AND 500
HPA HEIGHT FIELD, FAVOR A COMPROMISE OF THE 12Z ECMWF/12Z
UKMET/12Z CANADIAN/12Z GFS/12Z NAM, WHICH ROUGHLY RESEMBLES THE
09Z SREF MEAN AT 500 HPA AND THE SURFACE.  FOR QPF AND WINTER
WEATHER CHOICES, SEE OUR QPF AND WINTER WEATHER DISCUSSIONS AND
GRAPHICS.


...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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