Prognostic Meteorological Discussion
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000
FXUS10 KWNH 220643
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
143 AM EST WED NOV 22 2017

VALID NOV 22/0000 UTC THRU NOV 25/1200 UTC

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

00Z MODEL PREFERENCES AND CONFIDENCE INTERVALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


SYSTEM APPROACHING THE WEST COAST SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND; CONFIDENCE ABOVE AVERAGE

THE 00Z GFS MOVES THIS SYSTEM A BIT QUICKER THAN THE OTHER
GUIDANCE, WHICH MIGHT BE DUE TO LIMITED CONVECTIVE/GRIDSCALE
FEEDBACK NOTED IN ITS FRIDAY SOLUTIONS WELL OFFSHORE CA.  ALOFT,
THE FLOW IS BECOMING WELL AMPLIFIED, WHICH SHOULD RESULT EITHER IN
A SLOWER MOVING SYSTEM OR A SYSTEM WITH LESS AMPLITUDE THAN THE
GFS IS ADVERTISING.  A COMPROMISE OF THE 00Z NAM, 00Z UKMET, 00Z
CANADIAN, AND 00Z ECMWF IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE.


SLOW MOVING MID-UPPER LEVEL TROUGH ALONG THE GULF COAST
SURFACE LOWS IN THE EASTERN GULF OF MEXICO/NEAR FLORIDA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF/GFS/UKMET BLEND; CONFIDENCE AVERAGE

STARTING FRIDAY, THE NAM STARTS DIVERGING FROM THE OTHER GUIDANCE
IN BECOMING DEEPER/SLOWER ALOFT/MORE WESTERLY AT THE SURFACE WITH
THIS SYSTEM -- ITS USUAL BIAS AT THIS TIME RANGE.  THE 00Z UKMET
IS FLATTER ALOFT AND EVENTUALLY MORE EASTWARD WITH THE SURFACE LOW
TRACK OFFSHORE THE SOUTHEAST.  THE 12Z GLOBAL ENSEMBLE SPREAD IS
NOT LARGE ENOUGH TO CAPTURE THE NAM OR UKMET SOLUTIONS, SO THEY
ARE NOT PREFERRED.  THE 00Z GFS SHOWS EVIDENCE OF
CONVECTIVE/GRIDSCALE FEEDBACK ACROSS FL WHICH DEEPENS ITS LOW AS
WELL.  HOWEVER, ITS SURFACE TRACK RESEMBLES THE OTHER GUIDANCE.
TO ACCOUNT FOR THE UNCERTAINTY, A COMPROMISE OF THE 00Z GFS, 00Z
CANADIAN, AND 00Z ECMWF IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE
CONFIDENCE. FOR QPF CONSIDERATIONS...SEE OUR QUANTITATIVE
PRECIPITATION DISCUSSION (QPFPFD).


SYSTEM MOVING NEAR/NORTH OF THE US/CANADIAN BORDER
UPPER TROUGH AFFECTING THE GREAT LAKES/NORTHEAST WED-FRI
SURFACE LOW MOVING INTO ATLANTIC CANADA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE FEATURES.  A
COMPROMISE OF THE 00Z CANADIAN, 00Z UKMET, 00Z NAM, 00Z GFS, AND
00Z ECMWF IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE.


www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

Roth
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