Prognostic Meteorological Discussion
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000
FXUS10 KWNH 280634
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 AM EDT WED SEP 28 2016

VALID SEP 28/0000 UTC THRU OCT 01/1200 UTC

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

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


BINARY INTERACTION NEAR THE WEST COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: BELOW AVERAGE

THERE ARE MODEST DIFFERENCES ALOFT NEAR AND OFFSHORE THE WEST
COAST WHICH APPEAR TO HAVE BEARING ON THE MOVEMENT OF THE SYSTEM
IN THE MIDWEST/OHIO VALLEY.  THE 00Z GFS IS THE SLOWEST/MOST
AMPLIFIED WITH THE TROUGH NEAR CA FRIDAY NIGHT, MAINLY BECAUSE IT
IS THE MOST NORTHERLY WITH THE DEEP CYCLONE OFFSHORE SOUTHWEST
CANADA.  BINARY/FUJIWHARA INTERACTIONS SUCH AS THESE ARE TRICKY,
AND LEAD TO BELOW AVERAGE FORECAST CONFIDENCE.  FOR THE TIME
BEING, PREFER A COMPROMISE OF THE AVAILABLE GUIDANCE, WHICH WOULD
PLACE LESS WEIGHT ON THE 00Z GFS SOLUTION.


DEEP CYCLONE ACROSS MIDWEST DOUBLING BACK TOWARDS MI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF/UKMET COMPROMISE
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE 00Z GFS ENDS UP BEING THE FARTHEST SOUTH WITH THIS SYSTEM BY
FRIDAY NIGHT.  THIS APPEARS TO BE DUE TO ITS SLOWER UPPER TROUGH
OFFSHORE THE WEST COAST AND DOWNSTREAM RIDGING ACROSS THE PLAINS
WHICH IS MORE ENHANCED THAN MUCH OF THE GUIDANCE.  WE HAVE TWO
COMPETING INFLUENCES WITH THIS SYSTEM`S MOVEMENT -- THE
STRONG/NORTHERLY DISPLACED SUBTROPICAL RIDGE NORTH OF THE SARGASSO
SEA AND THE UPSTREAM TROUGH/RIDGE COUPLET.  NO MATTER WHICH
SOLUTION YOU PICK, THE ATLANTIC RIDGE IS STRONG AND SHOULD LEAD TO
SOME NORTHERLY RETURN AFTER THURSDAY NIGHT AS THE RIDGE IN THE
PLAINS IS WEAKENED BY A SHORTWAVE MOVING THROUGH MT.  FOR NOW,
WILL CONSIDER THE 00Z GFS A LOWER PROBABILITY ALTERNATIVE SCENARIO
AND GO WITH A COMPROMISE OF THE 00Z UKMET/00Z ECMWF -- WHICH IS
CLOSEST TO THE 12Z ECMWF/00Z GEFS MEAN SOLUTIONS -- WITH SLIGHTLY
BELOW AVERAGE CONFIDENCE.


CLOSED LOW LIFTING OUT OF THE SOUTHWEST
SHORTWAVE LIFTING MOVING THROUGH MT EARLY FRI MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE SYSTEMS.  A
COMPROMISE OF THE AVAILABLE GUIDANCE IS PREFERRED TO DEAL WITH ANY
LINGERING DETAIL ISSUES WITH ABOVE AVERAGE CONFIDENCE.



...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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