Prognostic Meteorological Discussion
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000
FXUS10 KWNH 041723
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
122 PM EDT TUE AUG 04 2015

VALID AUG 04/1200 UTC THRU AUG 08/0000 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 APPEAR TO DEGRADE THEIR SHORT
RANGE FORECASTS.


CLOSED LOW APPROACHING CA THU NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE GUIDANCE IS IN GOOD AGREEMENT WITH THIS SYSTEM.


POSSIBLE CLOSED LOW MOVING ALONG WESTERN US/CAN BORDER
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NAM/ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE GUIDANCE SHOWS CONSIDERABLE SPREAD WITH THIS SYSTEM.  THE
SYSTEM IS MOVING OVER THE TOP OF A SOUTHERN STREAM RIDGE WOULD
TEND TO ARGUE FOR A FASTER SOLUTION...WHILE THE IDEA THAT IT IS
MOVING WITHIN THE SOUTHWEST PORTION OF AN OMEGA-TYPE BLOCK ACROSS
CANADA ARGUES FOR A SLOWER SOLN.  THE INTERMEDIATE GUIDANCE HERE
OF THE 00Z ECMWF/12Z NAM SPLIT THE DIFFERENCE AND A COMPROMISE OF
THE TWO IS PREFERRED WITH AVERAGE CONFIDENCE.


NORTHERN STREAM SHORTWAVES CROSSING THE DAKOTAS/MN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON NAM/NON UKMET COMPROMISE
CONFIDENCE: AVERAGE

THE 12Z UKMET BECAME EVEN MORE OUT OF SYNC WITH OTHER MODELS...NOW
SHOWING A RIDGE WHERE MOST OF THE OTHER MODELS SHOW A TROF BY
06/18Z.  THE NAM APPEARED TO BE OVERLY DEEP.  REMOVING THOSE TWO
LOOKS LIKE IT SHOULD YIELD A REASONABLE COMPROMISE WITH AVERAGE
CONFIDENCE.


SHORTWAVE CROSSING THE MID-SOUTH/SOUTHEAST WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS...04/00Z ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE GUIDANCE HAS TRENDED NOTICEABLY WEAKER WITH THIS SYSTEM SINCE
YESTERDAY.  THE 12Z CANADIAN REMAINED A STRONG OUTLIER -- ITS
USUAL BIAS.  THE 12Z NAM SURFACE LOW RESIDES COMPLETELY OUTSIDE
THE NORTHEAST FRINGE OF THE 00Z GLOBAL ENSEMBLE SPREAD BY FRIDAY
MORNING.  A COMPROMISE OF THE 12Z GFS AND 04/00Z ECMWF LOOKS
REASONABLE HERE.


LOW PRESSURE MOVING FROM GA COAST TO THE CAROLINA COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/NAM/CANADIAN COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE SYSTEM LOOKS BETTER IN TERMS OF CONVECTION AND THE FACT THAT
THE CIRCULATION HAD BECOME BETTER DEFINED.  THUS AM NOT INCLINED
TO SUMMARILY DISMISS THE STRONGER CANADIAN SOLN AS THE SYSTEM
PULLS EAST AND MERGES WITH A FRONTAL SYSTEM.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BANN

$$




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