Prognostic Meteorological Discussion
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FXUS10 KWNH 181828
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
227 PM EDT FRI APR 18 2014

VALID APR 18/1200 UTC THRU APR 22/0000 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.


DEEP CYCLONE/SHARPENING TROUGH OFFSHORE WRN NORTH AMERICA
UPPER TROUGH REACHING NEW ENGLAND TONIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THE GUIDANCE IS IN GOOD AGREEMENT WITH THESE SYSTEMS.  A GENERAL
MODEL COMPROMISE IS PREFERRED TO DEAL WITH ANY LINGERING DETAIL
ISSUES WITH ABOVE AVERAGE CONFIDENCE CONSIDERING THE MINIMAL MODEL
SPREAD.


SHORTWAVE ENTERING THE PACIFIC NW SAT REACHING MN MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  CLOSEST TO THE ECMWF
CONFIDENCE:  AVERAGE

THE 12Z NAM KEEPS THE BULK OF ITS MID-LEVEL ENERGY WELL NORTH OF
THE US/CANADIAN BORDER, WHICH LEADS TO A MUCH MORE NORTHERLY
SURFACE LOW THAT FALLS OUTSIDE THE 00Z GLOBAL ENSEMBLE SPREAD --
ITS SOLUTION WILL NOT BE PREFERRED.  THE 12Z GFS APPEARS TO USE
GRIDSCALE FEEDBACK ACROSS SOUTHERN MANITOBA AND NORTHERN MN TO
DEEPEN ITS MID-LEVEL LOW AS IT MOVES THROUGH THE REGION, WHICH
LEADS TO A MORE SOUTHERLY/DEEPER SURFACE LOW -- THIS IS ALSO NOT
PREFERRED.  THE 12Z CANADIAN SHOWS ITS USUAL STRONG BIAS WITH THIS
SYSTEM, THOUGH THE SYSTEM SHOULD SHARPEN SOME ALOFT DUE TO
INCREASED RIDGING UPSTREAM -- THIS IDEA RULED OUT THE WEAKER 12Z
UKMET SOLUTION.  BELIEVE THE 12Z ECMWF IS THE BEST FIT TO THE FLOW
PATTERN AND 00Z GLOBAL ENSEMBLE GUIDANCE, SO PREFER ITS SOLUTION
WITH AVERAGE CONFIDENCE CONSIDERING THE SPREAD SEEN IN THE CURRENT
DETERMINISTIC GUIDANCE.


SYSTEM APPROACHING MAINE SUNDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  NON-NAM COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THIS SYSTEM ALOFT IS MOVING OVER THROUGH WHAT SHOULD OTHERWISE BE
A BROAD NORTHERN STREAM RIDGE, WHICH ARGUES FOR A WEAKER SOLUTION
ALOFT.  THIS RULES AGAINST THE 12Z NAM, AND TOWARDS THE NON-NAM
CONSENSUS, WHICH IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE
CONSIDERING THE FLOW PATTERN IN WHICH IT IS EMBEDDED.


DEEP CYCLONE MOVING OFFSHORE THE SOUTHEAST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  NON-NAM COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THE 12Z NAM IS UNIQUELY WEAK ALOFT, WHICH LEADS TO A MUCH WEAKER
AND MORE SOUTHERLY SURFACE LOW TRACK.  IT FALLS COMPLETELY OUTSIDE
THE SOUTHWEST SIDE OF THE 00Z GLOBAL ENSEMBLE SPREAD.  A NON-NAM
COMPROMISE IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE CONSIDERING
ITS RELATIVELY SLOW PROGRESSION.



SYSTEM MOVING FROM THE SOUTHWEST INTO THE LWR MS VLY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  NON-NAM COMPROMISE
CONFIDENCE:  AVERAGE

THE NAM IS WEAKER WITH THIS SYSTEM WHEN COMPARED TO THE OTHER
GUIDANCE.  AS UPSTREAM RIDGING IS BUILDING, WE PREFER A NON-NAM
COMPROMISE WITH ABOVE AVERAGE CONFIDENCE BASED UPON THE SYNOPTIC
PATTERN IN WHICH THE SYSTEM IS EMBEDDED.


...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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