Prognostic Meteorological Discussion
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536
FXUS10 KWNH 030637
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 AM EST SAT DEC 03 2016

VALID DEC 03/0000 UTC THRU DEC 06/1200 UTC

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

00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SHORTWAVE AMPLIFYING INTO A CLOSED LOW ACROSS NORTHERN MEXICO
SAT/SUN LIFTS INTO TX BY MON SPURRING SURFACE LOW DEVELOPMENT IN
WESTERN GULF MON LIFTING INTO LOWER MS VALLEY

PREFERENCE: 12-00Z ECMWF/00Z UKMET BLEND
CONFIDENCE: AVERAGE

THE LARGE SPREAD IS PERSISTENT WITH TIMING ISSUES YET TO BE
RESOLVED ON THE FORWARD PROGRESSION OF THE 700 MB WAVE AND SURFACE
LOW REFLECTION ACROSS THE LOWER MS VALLEY INTO THE TN AND OH
VALLEYS.  THE NAM AND 21Z SREF MEAN ARE ON THE FASTER/NORTHERN
EDGE OF THE SOLUTION CLUSTER AND GFS/GEFS MEAN ON THE
SOUTHERN/SLOWER END. THE 12Z-00Z ECMWF CONTINUE TO BE SLOWER AND
MORE WOUND UP THAN THE 12 ECENS...WHICH REMAINS FASTER THAN THE
OPERATIONAL RUN IN MOVING THE SYSTEM NORTH ACROSS THE LOWER MS
VALLEY AND INTO THE OH VALLEY MON NIGHT.  THE 00Z UKMET HAS SLOWED
DOWN TO GET CLOSER TO THE OPERATIONAL ECMWF RUN..SO THE FASTER
UKMET TREND ON THE 12Z RUN HAS REVERSED.

CONTINUE TO PREFER THE MIDDLE OF THE CLUSTER UNTIL MODEL TO MODEL
AND ENSEMBLE TO MODEL DIFFERENCES GET RESOLVED...SO IN THIS CASE
THE MIDDLE IS FORMED BY THE LAST 3 RUNS OF THE ECMWF AND 00Z
UKMET.


SHORTWAVE CROSSING SOUTHWEST NORTHERN PLAINS SAT...WESTERN GREAT
LAKES SUNDAY...NEW ENGLAND MON

PREFERENCE: GFS/ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS SHOW A 700 MB WAVE CROSSING THE NORTHERN PLAINS TODAY
AND UPPER MS VALLEY SUNDAY BEFORE GRADUALLY DEAMPLIFYING AS IT
CROSSES THE GREAT LAKES SUN NIGHT AND MON...WHEN IT MOVES INTO
NY/NEW ENGLAND.  THE 00Z NAM AND 21Z SREF MEAN ARE FASTER IN
DEAMPLIFYING THE WAVE THAN THE ECMWF/GFS/UKMET.  THE
GFS/UKMET/ECMWF CLUSTER IS PREFERRED AND HAVE ABOVE AVERAGE
AGREEMENT ON THE TIMING AND EVOLUTION OF THE WAVE WITH LOW
PRESSURE WEAKENING CROSSING THE GREAT LAKES.  THIS PROVIDES ENOUGH
SUPPORT TO SUGGEST A GFS/UKMET/ECMWF MODEL BLEND AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.


...SHORTWAVE CROSSING THE PACIFIC NORTHWEST AND NORTHERN ROCKIES
SUN AND THEN NORTHERN PLAINS BY MONDAY/UPPER MS VALLEY MON NIGHT...

PREFERENCE: UKMET/ECMWF/NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE NEXT WAVE ENTERS THE PACIFIC NORTHWEST/VANCOUVER ISLAND FROM
THE NORTH PACIFIC ON SUNDAY MORNING.  THERE IS PRETTY GOOD
CLUSTERING AMONG THE 12Z ECMWF AND UKMET AS WELL AS THE ECENS MEAN
AND GEFS MEAN ACROSS THE NORTHWEST...WITH THE 00Z ECMWF A FEW
HOURS FASTER WITH THE WAVE.
DIFFERENCES MAGNIFY IN THE NORTHERN PLAINS/UPPER MS VALLEY MON/MON
NIGHT. THE GFS/GEFS MEAN HAVE A HIGHER AMPLITUDE 700 MB WAVE WHICH
RESULTS IN THE SURFACE LOW PRESSURE DEVELOPING FURTHER NORTH THAN
IN THE NAM/UKMET/ECMWF. THE EC ENSEMBLE MEAN DEVELOPS LOW PRESSURE
00Z TUE EVEN FURTHER SOUTH THAN THE OPERATIONAL RUN NEAR THE MN/SD
BORDER.  AS SUCH WILL PREFER A 00Z NAM/UKMET/ECMWF BLEND AT
SLIGHTLY ABOVE AVERAGE CONFIDENCE.


LOW DEVELOPING OVER THE NORTHEAST PACIFIC AND MOVING JUST OFF
VANCOUVER ISLAND 12Z MON AND INTO WA/OR THROUGH MON NIGHT

PREFERENCE: BLEND OF ECMWF/UKMET/NAM
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A 700 MB WAVE FORMS OVER THE NORTHEAST PACIFIC AND MOVES SOUTHEAST
TOWARDS VANCOUVER ISLAND  SUNDAY NIGHT AND ACROSS WA/ADJACENT OR
MON AND MON NIGHT. THE 12Z UKMET WAS A BIT DEEPER WITH THE WAVE AS
IT CROSSES INTO THE PACIFIC NORTHWEST AT THE END OF DAY 3 BUT IS A
LITTLE WEAKER ON THE 00Z RUN. THIS RESULTS IN A GOOD CLUSTER OF
SOLUTIONS AMONG THE NAM/GFS/ECMWF/UKMET.
THIS SUGGESTS USING A CONSENSUS BASED APPROACH...OR BLENDING THE
00Z NAM/12Z ECMWF/00Z UKMET.
THE 00Z GFS HAS A SECONDARY LOW PRESSURE CENTER 12Z TUE OFF THE OR
COAST NOT IN THE OTHER MODELS.  THE 0Z0 ECMWF TRENDED A FEW HOURS
FASTER WITH THE 700 MB WAVE ACROSS ID...WHICH WAS ALSO SEEN IN THE
00Z GEFS MEAN.

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

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

PETERSEN

$$





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