Prognostic Meteorological Discussion
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000
FXUS10 KWNH 030448
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1148 PM EST FRI DEC 02 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: 00-12Z ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

THE LARGER 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 00Z-12Z 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 12Z UKMET WAS CLOSE TO THE 12Z ECMWF ENSEMBLE MEAN
POSITION BY 12Z TUE...BUT THE 00Z RUN IS SLOWING DOWN AND IS
CLOSER TO THE ECMWF LIKE IT WAS LAST NIGHT...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 2 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 ECMWF AND UKMET AS WELL AS THE ECENS MEAN AND
GEFS MEAN ACROSS THE NORTHWEST...WITH DIFFERENCES MAGNIFYING 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 RESULT SIN 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.

...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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