Prognostic Meteorological Discussion
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FXUS10 KWNH 021836
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
136 PM EST FRI DEC 02 2016

VALID DEC 02/1200 UTC THRU DEC 06/0000 UTC

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

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

SHORTWAVE AMPLIFYING 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: 12Z GFS/ECMWF BLEND
CONFIDENCE: AVERAGE

THE LARGER SPREAD CONTINUES TO EVAPORATE WITH THE CAMPS FROM A FEW
DAYS AGO SWAPPING POSITIONS: GFS/UKMET FASTER  AND ECMWF/NAM
SLOWER.  THE 00Z ECMWF CONTINUES TO BE SLOWER AND MORE WOUND UP
THAN THE MAJORITY OF THE 00Z ECENS MEMBERS MAKING THE ECENS MEAN
UNCHARACTERISTICALLY FAST ESPECIALLY IN A DEEP SOUTHERN CUT-OFF
ENVIRONMENT.

OVERALL MODELS ARE IN GOOD ALIGNMENT IN EVOLUTION
SHAPE/TIMING/STRENGTH THROUGH THE NORTHERN MX PLATEAU THROUGH SUN.
 TIMING/RETENTION OF STRENGTH DIFFERENCES EXPAND THE SPREAD
SLIGHTLY AS THE UPPER LOW CROSSES THE NORTHERN SIERRA MADRE
ORIENTAL.  THIS IS MOST EVIDENT IN THE 12Z NAM...NOW THE SLOWEST
RETAINING THE STRENGTH OF THE UPPER LOW.  THIS IS OPPOSITE OF ITS
POSITION IN THE SOLUTION OVER THE PAST FEW DAYS...MAKING IT LOWER
CONFIDENCE IN USING IT WITHIN THE BLEND.  THE 12Z GFS LIKE THE 06Z
GFS ARE A BIT WEAKER TRAVERSING MEXICO AND BECOME FASTER EVEN AND
BECOME AN OPEN WAVE BY MON EVENING COMPARED TO THE 00Z GFS/06Z
GEFS BUT IS ALSO COMPARABLE TO THE 00Z GFS PARALLEL AND 00Z ECMWF.
 THE 00Z UKMET/CMC ALSO MATCH WITH TIMING OF THE ECMWF/GFS THOUGH
THE UKMET IS A BIT FURTHER NORTH WITHIN THE SUITE.  ALL CONSIDERED
A NON-NAM BLEND (NOR 09Z SREF/00Z ECENS MEAN) IS PREFERRED IN THE
A BLEND.  CONFIDENCE IN THESE SOLUTIONS IN THE BLEND IS INCREASING
TO THE POSITIVE SIDE OF AVERAGE.

19Z UPDATE: THE 12Z GEFS MEMBERS CONTINUE TO SHOW THE UNCERTAINTY
WITH RESPECT TO DAY 3 IN THE TIMING/HOW LONG TO MAINTAIN A CLOSED
SYSTEM AND THEREFORE THE MEAN LAGS THE OPERATIONAL 12Z GFS.  THIS
IS FURTHER COMPOUNDED BY THE 12Z UKMET TRENDING FASTER WHILE THE
12Z CMC TRENDED SLOWER IN THE REALM OF THE 12Z NAM.  THE 12Z ECMWF
CONTINUES WITH CONSISTENT TIMING BUT LIKE THE GFS IS A BIT WEAKER
THAN PRIOR RUNS.  THE MIDDLE GROUND IS BEST REPRESENTED BY THE 12Z
GFS/ECMWF AND SO WILL EXCLUDE THE 12Z VERSIONS OF THE UKMET/CMC
FROM THE PREFERENCE.  CONFIDENCE REMAINS AVERAGE.


SHORTWAVE CROSSING SOUTHWEST CANADA FRI...NORTHERN PLAINS
SAT...WESTERN GREAT LAKES SUNDAY...NEW ENGLAND MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

LINGERING SHORTWAVE ENERGY ACROSS W WY AT THIS TIME WILL BE
LIFTED/COMBINED WITH ENERGY AT THE LEADING EDGE OF 150+ KT JET
ENTERING THE PACIFIC NORTHWEST TODAY.  AS THE WAVE CONSOLIDATES
CROSSING THE ROCKIES THERE REMAINS SOME WEAK PHASED NATURE WITH
THE SOUTHERN STREAM CUT-OFF AND INCREASE IN AMPLIFICATION THE
CENTRAL PLAINS BEFORE DECOUPLING AND SWINGING NORTHEASTWARD
THROUGH THE GREAT LAKES/NEW ENGLAND SUN AND MON RESPECTFULLY.  THE
ENSEMBLES CONTINUE TO SHOW A SLOWING TREND WITH INCREASED
AMPLIFICATION TOWARD THE MOST AMPLIFIED EXAMPLE IN THE ECMWF
SOLUTION.  THOUGH THE 12Z GFS REMAINS SLIGHTLY FASTER AND LESS
AMPLIFIED, IT IS TRENDING MORE SO THE THE ECMWF/SLOWING A BIT.
THIS WAS ALSO SUPPORTED BY THE TREND IN THE 12Z NAM AS WELL.  THE
00Z CMC/UKMET ARE ALSO GENERALLY SUPPORTIVE OVERALL.  THIS
PROVIDES ENOUGH SUPPORT TO SUGGEST A GENERAL MODEL BLEND AT
SLIGHTLY ABOVE AVERAGE CONFIDENCE.

19Z UPDATE: THE 12Z UKMET/ECMWF CONTINUED THE TREND OF A MORE
SOUTHERN AMPLIFICATION TO THE WAVE CROSSING THE CENTRAL
PLAINS...WHILE THE 12Z CMC IS A BIT FASTER AND FLATTER. STILL THE
TIMING IS FAIR TO GOOD WITH THIS WAVE AND SENSIBLE WX SEEMS TO BE
MATCHED WELL ENOUGH TO KEEP WITH THE INITIAL PREFERENCE.


SHORTWAVE CROSSING SOUTHWEST CANADA TO THE NORTHERN ROCKIES AND
THEN NORTHERN PLAINS BY MONDAY
WITH SURFACE FRONTAL ZONE IN NORTHERN/CENTRAL PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/UKMET/ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

POTENT SHORTWAVE CROSSING THE CENTRAL BC COAST TRAVERSES THE
CANADIAN ROCKIES INTO THE CENTRAL PRAIRIES AND WILL ACT AS A DEEP
FULCRUM UPPER LOW WITH RESPECT TO THE NEXT WAVE ENTERING THE
PACIFIC NORTHWEST/VANCOUVER ISLAND FROM THE NORTH PACIFIC ON
SUNDAY MORNING.  THE TRENDS HAVE BEEN TOWARD A FLATTER SLIGHTLY
SLOWER SOLUTION...THIS WAS BEST EXEMPLIFIED BY THE 12Z GFS WHICH
TRENDED A BIT SLOWER AND WEAKER AS THE WAVE CROSSES THE NORTHERN
US ROCKIES INTO THE CENTRAL PLAINS.  THIS IS ALSO CLOSER TO THE
00Z ECMWF AND UKMET AS WELL AS THE 00Z ECENS MEAN AND 06Z GEFS
MEAN PROVIDING A BIT MORE CONFIDENCE IN THE EVOLUTION.  THE 12Z
NAM IS FLATTER THAN OLDER RUNS OF THE NAM OR GFS BUT IS ALSO A BIT
SLOWER CROSSING INTO THE PLAINS WHICH IS ALSO DENOTED IN THE
SURFACE WX PATTERN.  THOUGH THE 00Z CMC IS EVEN SLOWER THAN THE
NAM MAKING IT A CLEAR OUTLIER.  AS SUCH WILL PREFER A 12Z GFS AND
00Z UKMET/ECMWF BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.

19Z UPDATE: WHILE THE 12Z CMC TRENDED FASTER...IT REMAINS ON THE
SLOW SIDE OF THE SUITE AND ALIGNS BETTER WITH THE LESSER PREFERRED
TIMING OF THE 12Z NAM.  THE 12Z ECMWF/UKMET BOTH TRENDED A LITTLE
BIT SLOWER TRENDING IN THE NORTHERN STREAM ACROSS CENTRAL
CANADA...LEADING TO A FURTHER SOUTHWARD SURFACE REFLECTION EXITING
THE NORTH CENTRAL ROCKIES ALONG THE COLD FRONT OPPOSED TO THE
DEEPER/FURTHER NORTH SOLUTION PRESENTED BY THE GFS.  WILL KEEP
INITIAL PREFERENCE OF GFS/UKMET/ECMWF BUT WEIGHT HIGHER TOWARD THE
ECMWF/UKMET.


LOW DEVELOPING OVER THE NORTHEAST PACIFIC AND MOVING TOWARDS
VANCOUVER ISLAND 12Z MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHT ABOVE AVERAGE

A CLOSED LOW FORMS OVER THE GULF OF ALASKA BY SUNDAY AND GIVEN
DOWNSTREAM SLOWER SHORTWAVE...THIS WAVE HAS TRENDED A BIT FASTER
OVERALL WITHIN THE ENSEMBLE SOLUTIONS WITH LESS SHORTWAVE RIDGING
EXPECTED BETWEEN THE TWO SYSTEMS.  THE 12Z UKMET IS A BIT DEEPER
WITH THE WAVE AS IT CROSSES INTO THE PACIFIC NORTHWEST AT THE END
OF DAY 3 BUT STILL IN ALIGNMENT WITH THE TIMING OF THE ENSEMBLES
WHICH ARE SUPPORTED CLOSEST BY THE 12Z NAM/GFS AND 00Z ECMWF.
THE 00Z CMC HAVING A THE SLOWEST DOWNSTREAM FEATURE LEADS TO
CLOSER INTERACTION AND LEADS TO A DISTINCTLY DIFFERENT ORIENTATION
OF THE WAVE MAKING IT APPEAR FASTER IN THE MASS FIELDS.  ALL
CONSIDERED WILL PREFER A NON-CMC SOLUTION FOR THIS SYSTEM AT
SLIGHTLY ABOVE AVERAGE CONFIDENCE.

19Z UPDATE: LITTLE CHANGE IN THE 12Z UKMET/ECMWF SOLUTIONS TO KEEP
GOOD CONFIDENCE IN INITIAL THOUGHTS.  THE 12Z CMC BEING SLIGHTLY
FASTER DOWN STREAM SHOW SOME POSITIVE TRENDS TOWARD CONSENSUS BY
THE END OF DAY 3 TO THIS SYSTEM BUT REMAINS FLATTER AND LESS
FAVORABLY ORIENTED WITH THIS WAVE TO KEEP A NON-CMC BLEND AT THIS
POINT.

...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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