Prognostic Meteorological Discussion
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000
FXUS10 KWNH 200425
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1124 PM EST SUN NOV 19 2017

VALID NOV 20/0000 UTC THRU NOV 23/1200 UTC

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

00Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


STRENGTHENING UPPER TROUGH OVER THE GULF OF MEXICO
BAROCLINIC LOW IN THE SOUTHEAST GULF WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CLOSEST TO UKMET; CONFIDENCE AVERAGE

DESPITE GOOD AGREEMENT UPSTREAM ACROSS THE PLAINS AND WEST, THERE
ARE SUBSTANTIAL ISSUES ALOFT IN THIS REGION WHICH LEAD TO A BIT OF
SPREAD AT THE SURFACE.  THE 12Z ECMWF WAS THE SHARPEST (THOUGH
WEAKEST WITH THE 500 HPA HEIGHT FIELD) ALOFT, WHICH LED TO THE
MOST SOUTHWESTERLY SURFACE LOW.  THE 12Z CANADIAN WAS MOST
PROGRESSIVE.  THE 00Z GFS HAD THE STRONGEST BUNDLE OF ENERGY ALOFT
THE FARTHEST NORTH.  THE AMPLIFYING FLOW PATTERN SUGGESTS LOWER
MID-LEVEL HEIGHTS THAN THE ECMWF ADVERTISES, A FARTHER SOUTH
MID-LEVEL BUNDLE OF ENERGY THAN SEEN IN THE 00Z GFS, AND LESS
PROGRESSION THAN ADVERTISED BY THE CANADIAN.  THE GUIDANCE CLOSEST
TO THE 12Z/18Z ENSEMBLE MEANS ARE THE 00Z NAM AND 12Z UKMET ALOFT,
BUT THE 00Z NAM HAS A BONUS SURFACE LOW OFFSHORE NORTHEAST FL NOT
SEEN IN THE OTHER GUIDANCE WHICH DISTORTS ITS FORECAST RAINFALL.
A SOLUTION CLOSEST TO THE 12Z UKMET IS PREFERRED WITH AVERAGE
CONFIDENCE.


NORTHEAST WEDNESDAY INTO THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NAM/ECMWF/GFS COMPROMISE; AVE CONFIDENCE

LIKE THE SOUTHEAST THERE ARE SUBSTANTIAL ISSUES ALOFT.  THE 12Z
CANADIAN/UKMET ARE THE MOST AMPLIFIED/SHARPEST WITH THIS ENERGY.
SINCE THE NORTHERN STREAM UPPER PATTERN IS BROAD, BELIEVE THEY ARE
TOO STRONG ALOFT AND TOO FAR WEST WITH THEIR SURFACE LOW
PROGRESSION.  WHILE THE 12Z ECMWF AND 00Z GFS SHOW UNUSUAL
CONVECTIVE FEEDBACK WITH A SURFACE LOW THEY TAKE INTO ATLANTIC
CANADA, THEIR SOLUTIONS DO NOT APPEAR TO CONTORT THE RAINFALL
PATTERNS TOO STRONGLY ACROSS THE NORTHEAST.  A COMPROMISE OF THE
00Z NAM, 00Z GFS, AND 12Z ECMWF IS PREFERRED WITH AVERAGE
CONFIDENCE.


WARM FRONT LIFTING NORTH NEAR THE NORTHWEST TUESDAY
DEEP LAYER CYCLONE OFFSHORE SOUTHWEST CANADA/THE NORTHWEST
LOW MOVING INTO THE NORTHERN PLAINS/MIDWEST WED/THU
SURFACE LOW MOVING BY THE CENTRAL US/CAN BORDER MON & TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE SYSTEMS.  A
COMPROMISE OF THE 00Z NAM, 00Z GFS, 12Z CANADIAN, 12Z UKMET, AND
12Z ECMWF IS ADVISED 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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