Prognostic Meteorological Discussion
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000
FXUS10 KWNH 011622
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1121 AM EST THU DEC 01 2016

VALID DEC 01/1200 UTC THRU DEC 05/0000 UTC

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

12Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SHORTWAVE AMPLIFYING IN THE SOUTHWEST FRI WITH A CLOSED LOW
FORMING AND ACROSS NORTHWEST MEXICO SAT SPURRING LEE SURFACE LOW
ACROSS NEAR S TX/NE MEXICO BY MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/06Z GEFS/00Z UKMET BLEND
CONFIDENCE: AVERAGE

OVERALL TRENDS HAVE BEEN TOWARD A COMMON CONSENSUS YET THERE
REMAINS A MODERATE TO HIGH SPREAD IN THE MODEL SOLUTIONS.  THE 00Z
ECMWF IS A STAND OUT WESTERN OUTLIER TO THE 00Z ECENS MEAN...DAY
TO DAY ENSEMBLE SPAGHETTI ANALYSIS SHOWS PERSISTENT 12Z/00Z
WAFFLING WITH THE ECENS MEAN AND GIVEN THE PROGRESSIVE STRONGER
WESTERLY FLOW FURTHER NORTH IT APPEARS TO BE A BIT TOO PHASED
GIVEN THE GENERAL CONSENSUS IN DEPTH OF LATITUDE THE CUT-OFF MAKES
INTO MEXICO.  WPC MEDIUM RANGE CONTINUES TO FAVOR A GFS/GEFS
SOLUTION FOR THIS SYSTEM FOR THE LAST FEW DAYS AND SEE NO
SIGNIFICANT REASON TO DEVIATE AT THIS TIME...THOUGH BEING A FAR
WESTERN SOLUTION THE 00Z OPERATIONAL ECMWF MAY HAVE SOME UTILITY
AT LOW WEIGHTING IN THE PREFERRED BLEND.

THE 12Z NAM CONTINUES TO PRESENT A DEEP TROF WITH A TIGHT INNER
CORE (THOUGH LESSENING WITH EACH RUN TOWARD THE GFS/ECWMF
APPEARANCE)...YET IS IS ALSO QUITE FAST SHIFTING EASTWARD AND IS
NOT WITHIN THE CURRENT PREFERENCE.  THE 12Z GFS TRENDED A BIT
WEAKER WITH THE SHORTWAVE ENERGY DIGGING OUT THE CLOSED SYSTEM.
THIS RESULTS IN LESS OF DROP IN LATITUDE AND SLIGHTLY
FASTER/EASTWARD SHIFT...WHICH WAS FIRST HINTED AT BY THE 00Z
PARALLEL GFS SOLUTION (BOTH MATCHING QUITE WELL).  THIS ALSO
ALIGNS WITH THE SHIFT EASTWARD SEEN IN THE 00 UKMET...FOR GOOD
ALIGNMENT OF THE TROF BY THE END OF DAY 3.  AS SUCH WPC PREFERENCE
IS A BLEND OF THE 12Z GFS/00Z UKMET AND 06Z GEFS SOLUTION.
CONFIDENCE IS RISING BUT REMAINS ON THE LOWER SIDE OF AVERAGE
GIVEN THE REMAINING SPREAD.


GREAT LAKES/NORTHEAST COASTAL LOW AND ASSOCIATED FRONTS EXITING
NORTHEAST THROUGH SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE 12Z NAM CONTINUES TO BE A BIT MORE AMPLIFIED BY SAT WITH THE
INNER CORE AS IT SHIFTS EAST THROUGH NORTHEAST NEW ENGLAND ON SAT
IN COMPARISON TO THE REST OF THE SUITE.  STILL GIVEN THESE
MINOR MASS DIFFERENCES EXIST THERE IS NO REASON TO SUGGEST ONE
PARTICULAR SOLUTION OVER ANOTHER. AS SUCH A GENERAL MODEL BLEND
SHOULD COVER THE UPPER LOW, SURFACE REFLECTIONS IN ONTARIO/QUEBEC
AND COASTAL DEVELOPMENT IN NEW ENGLAND INCLUDING THEIR
DEPTH/STRENGTH THROUGH THE REMAINING TIME AFFECTING THE CONUS.


SHORTWAVE CROSSING SOUTHWEST CANADA FRI INTO SAT TRACKING ACROSS
THE NORTHERN PLAINS TOWARD THE WESTERN GREAT LAKES BY SUNDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/GFS AND 00Z UKMET BLEND
CONFIDENCE: AVERAGE

A STRONG 150+ KT JET STREAK APPROACHES AND REACHES VANCOUVER
ISLAND ON SAT.  THE WAVE DOWNSTREAM FROM THE JET MAX WILL BEGIN TO
AMPLIFY ACROSS THE SOUTHERN CANADIAN/NORTHERN U.S. ROCKIES AND
SUPPORT A WEAK SURFACE DEVELOPMENT IN THE LEE ACROSS SW
SASKATCHEWAN BY SAT EVENING.   THEREAFTER MODEL SPREAD INCREASES
SLIGHTLY AS THE TROF AMPLIFIES AND COLLECTS ANY REMAINING ENERGY
OF THE PRECEDING WAVE THAT SHEARED THE BULK OF ENERGY SOUTH AS IT
SHIFTS INTO THE CENTRAL PLAINS.  THE MORE ENERGY REMAINING PHASED
WITH THE SOUTHERN STREAM LEADS TO DEEPER AMPLIFICATION OF THE WAVE
AS A WHOLE CROSSING INTO THE WESTERN GREAT LAKES BY SUN NIGHT.
THIS INCLUDES THE 00Z UKMET/CMC/ECMWF AND LESSER SO 12Z NAM/GFS.
THE 12Z GFS DID TREND A BIT MORE AMPLIFIED THAN THE 00Z/06Z RUNS
BUT REMAINS A BIT FASTER THAN THE 12Z NAM/00Z UKMET.

THE 09Z SREF SEEMS MOST OUT OF PLACE OVERALL WITH THE TIMING AND
SHAPE OF THE SOLUTION 70-90 DEGREES DIFFERENT WITH THE HEIGHT
PACKING OVER THE OH VALLEY BY DAY 3.  PREFERENCE TOWARD LESS
INTERACTION WITH THE SOUTHERN STREAM CUT-OFF SEEMS MORE REASONABLE
GIVEN DIFFERENCES THERE (SEE ABOVE).  AS SUCH WILL PREFER THE 12Z
GFS AND INCLUDE THE 12Z/00Z UKMET TO HEDGE SOME OF THE HIGHER
AMPLIFIED SOLUTIONS PRESENTED IN THE ENSEMBLE SUITE.  CONFIDENCE
IS QUITE HIGH THROUGH EARLY SAT...BUT EVENTUALLY REDUCES TO
AVERAGE BY SUN.


SHORTWAVE TRACKING INTO NW WA/VANCOUVER ISLAND EARLY SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/CMC/ECENS MEAN AND 06Z GEFS MEAN
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE MODELS START TO BUCKLE THE WESTERLY ONSHORE FLOW WITH A LOW
AMPLITUDE WAVE CROSSES THE NORTHEAST PACIFIC SUN PRECURSORY TO THE
DEEPER WAVE/CLOSING OFF LOW DEVELOPING IN THE GULF OF AK.   THE
12Z GFS FOLLOWED BY THE 12Z NAM ARE MORE AGGRESSIVE AND AMPLIFIED
WITH THIS WAVE SUPPORTING A DEEP SURFACE CYCLONE LEE OF THE
NORTHERN MT ROCKIES BY THE END OF DAY 3.  THE 06Z GEFS DOES
SUPPORT A DEEPER WAVE THAN THE FLATTER 00Z NON-NCEP MODELS AND
ECENS MEAN...YET THERE APPEARS TO BE A MODERATE SPREAD IN THE GEFS
SOLUTIONS TO SUGGEST THE 12Z GFS IS A BIT TOO AMPLIFIED AND FAST.
AS SUCH WILL FAVOR THE MORE TEMPERED/SLOWER 00Z ECMWF/UKMET/CMC
WITH INCLUSION OF THE 06Z GEFS IN THE PREFERENCE.  CONFIDENCE IS
SLIGHTLY BELOW AVERAGE GIVEN THE TIMING/AMPLITUDE OF THE WAVE ARE
NOT WELL ESTABLISHED IN CONTINUITY WITH CONTINUED RUN TO RUN
VARIABILITY EXPECTED.


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

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

GALLINA

$$





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