Prognostic Meteorological Discussion
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000
FXUS10 KWNH 251621
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1120 AM 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 NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


MERGING SHORTWAVE MOVING INTO THE PLAINS WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: TOWARDS THE ECMWF
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 GUIDANCE, WHICH IS CLOSE TO THE 00Z ECMWF, 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: TOWARD THE GFS
CONFIDENCE: AVERAGE

THE GUIDANCE SHOWS SOME SPREAD HERE, WITH THE 12Z GFS SPLITTING
THE DIFFERENCE IN THE DETERMINISTIC AND GLOBAL ENSEMBLE SPREAD.  A
SOLUTION TOWARDS THE 12Z GFS 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
QPF/PRECIPITATION/WINTER WEATHER FORECAST.  IN REVIEWING THE 00Z
ECMWF, 12Z NAM, AND 12Z GFS, ALL THREE HAVE WHAT APPEAR TO BE
CONVECTIVE FEEDBACK BULL`S EYES CONTAMINATING THEIR SOLUTIONS.
THE ECMWF`S SLOWS DOWN THE OVERALL CYCLONE MORE THAN THE OTHER
GUIDANCE STARTING TUESDAY NIGHT.  THE NAM`S BULL`S EYES OVER THE
GULF STREAM OFFSHORE THE SOUTHEAST APPEAR TO CAUSE AN EASTWARD
SHIFT IN ITS 12Z SOLUTION AT THE SURFACE AND ALOFT.  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 OF THE OVERALL SYSTEM DUE TO AN
INVADING SHORTWAVE ROUNDING ITS SOUTHWEST SIDE ON TUESDAY, WHICH
WOULD LEAD TO A LESS EVEN 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/00Z 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 00Z
ECMWF/00Z UKMET/00Z 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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