Prognostic Meteorological Discussion
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000
FXUS10 KWNH 290414
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1213 AM EDT MON JUN 29 2015

VALID JUN 29/0000 UTC THRU JUL 02/1200 UTC

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

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


SHORTWAVE MOVING INTO THE NORTHERN PLAINS WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THERE ARE TWO CAMPS OF SOLUTIONS -- THE SLOWER 12Z CANADIAN (WHICH
IS ALSO STRONGER)/00Z GFS CAMP AND THE QUICKER 12Z ECMWF/00Z
NAM/12Z UKMET CAMP.  BOTH THE CANADIAN AND UKMET APPEAR TO BE
SHOWING THEIR USUAL BIASES, IMPLYING AN INTERMEDIATE SOLUTION IS
IDEAL.  PREFER A GENERAL MODEL COMPROMISE, WHICH SHOULD RESEMBLE A
COMPROMISE OF THE 12Z ECMWF/00Z GFS BEST FOR THE TIME BEING.


SYSTEM LIFTING OVER THE WESTERN RIDGE INTO THE PLAINS/MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/ECMWF/NAM COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z CANADIAN/12Z UKMET ARE SLIGHTLY QUICKER/DEEPER WITH THIS
SYSTEM WHICH SPAWNS AN ELONGATED SURFACE LOW ACROSS THE MID-SOUTH.
 AT THE SURFACE, THE 18Z GEFS MEAN IS MORE NORTHERLY WITH THE
SURFACE FEATURE, WHICH DOES NOT FIT IN WELL WITH THE 12Z GLOBAL
ENSEMBLE GUIDANCE (GEFS INCLUDED).  CONSIDERING THE AMPLIFICATION
OF THE EASTERN TROUGH, BELIEVE THE 18Z GEFS MEAN IS LESS THAN
IDEAL.  THE BIGGEST FLY IN THE OINTMENT WHICH MIGHT PREVENT A MORE
AMPLIFIED CANADIAN/UKMET SOLUTION IS THAT THERE IS AN UPSTREAM
SHORTWAVE NEAR THE US/CANADIAN BORDER WEDNESDAY NIGHT.  PREFER A
COMPROMISE OF THE 00Z GFS/00Z NAM/12Z ECMWF HERE WITH SLIGHTLY
ABOVE AVERAGE CONFIDENCE.


UPPER LOW SLOWLY RETROGRADING THROUGH MEXICO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CANADIAN COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z CANADIAN RETROGRADES THIS SYSTEM QUICKER WESTWARD THAN
SEEN IN THE OTHER DETERMINISTIC GUIDANCE.  THE SYSTEM APPEARS TO
RESIDE IN AN AREA WITH MINIMAL STEERING (COL) TO THE SOUTHEAST OF
A RIDGE ACROSS THE WEST AND WEST OF A WEAK SEGMENT OF THE
SUBTROPICAL RIDGE.  IN ADDITION, DETERMINISTIC GUIDANCE
OCCASIONALLY RETROGRADES SYSTEMS IN THE TROPICS/SUBTROPICS TOO
QUICKLY TO THE WEST.  PREFER THE SLOWER NON-CANADIAN GUIDANCE WITH
THIS SYSTEM WITH ABOVE AVERAGE CONFIDENCE.


CYCLONES MOVING THOUGH THE GREAT LAKES INTO QUEBEC
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE GUIDANCE SHOWS REASONABLE AGREEMENT WITH THESE SYSTEMS.


...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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