Prognostic Meteorological Discussion
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FXUS10 KWNH 231857
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT FRI SEP 23 2016

VALID SEP 23/1200 UTC THRU SEP 27/0000 UTC

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

12Z MODEL EVALUATION INCLUDING PREFERENCE AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

DEEP CYCLONE IN UT SWINGING THROUGH WY TO THE CENTRAL US/CANADIAN
BORDER BY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GEFS/GFS/UKMET
CONFIDENCE: SLIGHTLY BELOW AVERAGE

MODEL AGREEMENT IS FAIRLY TIGHT THROUGH ABOUT 25/06Z SUNDAY AS
OVERALL TROF ELONGATES NORTH TO SOUTH (SEE SECTION BELOW FOR
ENERGY IN THE BASE OF THE TROF SUNDAY).  THE DEEP INNER CORE LIFTS
NORTHEAST INTO THE DAKOTAS AND BEGINS TO SHEAR; MODELS THEN START
TO DIFFERENTIATE MAINLY IN HOW THE INNER CORE DEVOLVES INTO
PROGRESSIVELY BLOCKY FLOW ACROSS EASTERN CANADA.  BY THE END OF
DAY 3...THERE ARE GENERALLY TWO CAMPS IN THE MODEL SUITE; NORTH
AND MORE AMPLIFIED OR FASTER, SOUTH AND MORE CONSOLIDATED.  THE
STRENGTH OF THE POSITIVE ANOMALY ACROSS HUDSON BAY FAVORS A
CYCLONE UNDERCUTTING THE ANOMALY WITH TIME.

TYPICAL BIASES SEEM TO BE IN PLAY LEADING TO THESE DIFFERENCES.
THE 00Z CMC IS FIRST TO BREAK FROM CONSENSUS BEING SLOW THOUGH
UNCHARACTERISTICALLY WEAK WITH THE FEATURE...THIS DELAYS ITS
OVERALL EVOLUTION KEEPING IT ON THE NORTHWESTERN FRINGE OF
GUIDANCE.  THE 00Z ECMWF THOUGH FASTER THAN THE CMC AND IN LINE
WITH THE REMAINING GUIDANCE RETAINS A STRONGER WOUND UP
SOLUTION...AND AS SUCH TAKES MORE TIME TO SHEAR OUT, SHIFTING THE
FOCUS NORTH ALLOWING ENERGY TO BE SHED NORTH OF THE DOWNSTREAM
RIDGE...AND HENCEFORTH SLOW TO RECONSOLIDATE INTO A MORE
CONCENTRIC CLOSED LOW TO UNDERCUT THE POSITIVE ANOMALY.  THE ECENS
MEMBERS SHOW SIGNIFICANT SPREAD BY DAY 3 WITH A LARGE SURFACE LOW
SCATTER TOO...REDUCING CONFIDENCE IN THE ECMWF COMPARED TO THE
GEFS WHICH WERE TIGHTER AND FURTHER SOUTH.  OVERALL THE 00Z/06Z
GEFS ARE THE MOST CENTRAL SOLUTIONS WITH SOME FASTER TREND NOTED
OVER THE LAST FEW RUNS.  THE 00Z UKMET BECOMES VERY DEEP BUT IS
ALSO THE FASTEST SOLUTION PROGRESSING INTO THE NORTH CENTRAL GREAT
LAKES BY 27/00Z TUES.  THE 12Z NAM SHOWS SIMILAR EVOLUTION AND
TIMING WITH THE UKMET...OVERALL BOTH NAM/UKMET ARE FASTER THAN THE
BULK OF ENSEMBLE RUNS BUT HAVE BEEN LEADING THE TREND OVER THE
LAST DAY OR SO AS WELL.  THE 12Z GFS SHOWS A SLIGHTLY DEEPER AND
NORTHERN RESULT COMPARED TO THE 00Z AND 06Z GEFS BUT ALSO RESULT
IN THE MOST CENTRIC SOLUTION (NOT MUCH OF A SURPRISE GIVEN THE
GEFS).

OVERALL WILL SUPPORT THE 06Z GEFS ALONG WITH THE 12Z GFS...THOUGH
LOW WEIGHTING INCLUSION OF THE 12Z NAM/00Z UKMET AND EVEN SOME 00Z
ECMWF MAY HELP IF DESIRED.  GIVEN DIFFERENCES BY DAY 3 SEEM TO BE
COMPOUNDING FROM SMALLER TIMING/STRENGTH DIFFERENCES CONFIDENCE IS
SLIGHTLY BELOW AVERAGE (MAINLY AFTER 25/06Z).

19Z UPDATE: THE 12Z ECMWF CONTINUES TO SUPPORT A MORE NORTHERLY
TRACK AND LIFT THE BULK OF THE MID TO UPPER LEVEL ENERGY NORTHWARD
LEADING TO A NARROWER NEGATIVE TILT TROF.  THE 12Z RUN ALSO BROKE
FROM PRIOR RUNS IN SUPPRESSING THE DOWNSTREAM RIDGE WHICH SEEMS
LESS LIKELY GIVEN THE OVERALL REGIME SETUP WITH THE DEEP CYCLONE
OVER NORTHEAST CANADA. THE 12Z CMC`S EVOLUTION SEEMS MORE ON PAR
WITH A CONCENTRIC UL IN THE UPPER MIDWEST/NORTHERN TIER BY MON BUT
CONTINUES TO  REMAIN SLOW AND FURTHER N THAN EARLIER PREFERENCE.
THE 00Z UKMET DID TREND A BIT SLOWER TOWARD THE GFS
SOLUTION...THOUGH REMAINING JUST A SHADE EAST OF THE NEW 12Z GEFS
(WHICH CONTINUED TO SHOW CONSISTENCY) IT LIKE THE 12Z NAM REMAIN
VERY FAST WITH THE FRONTAL ZONE ACROSS THE EASTERN MIDWEST/CENTRAL
GREAT LAKES BY MONDAY EVENING...SO STILL FAVORING A TIMING CLOSER
TOWARD THE 12Z GFS/GEFS HOWEVER WILL INCLUDE THE 12Z UKMET INTO
THE PREFERENCE. CONFIDENCE WAS INCREASED A SHADE BY THE
CONSISTENCY OF THE GEFS AND INCLUSION OF THE UKMET BUT OVERALL
REMAINS SLIGHTLY BELOW AVERAGE IN THE 12Z GEFS/GFS/UKMET BLEND.


BASE OF DEEP TROF BECOMING A CLOSED LOW IN NM SUN AND AND SHIFTING
INTO NORTHWEST MEXICO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/GEFS/ECMWF/CMC BLEND BLEND
CONFIDENCE: AVERAGE

ENERGY FROM THE BASE OF THE ABOVE TROUGH CLOSES OFF IN AN
ANTICYCLONIC WAVE BREAKING EVENT AS RIDGING BUILDS ACROSS THE
NORTHWEST...THE ENERGY EVENTUALLY DESCENDS ALONG THE BACK SIDE OF
THE MEAN TROF AND BEGINS TO DEEPEN/CONSOLIDATE AND SLIP SW FROM W
NM INTO NW MEXICO SUNDAY INTO MONDAY WITH FAIRLY GOOD AGREEMENT.
THE 00Z CMC IS A SOUTHERN OUTLIER WITH VERY LITTLE SUPPORT EVEN
FROM OTHER CMCE MEMBERS.  THE REMAINING DIFFERENCES ARE RELATED
GENERALLY TO THE LONGITUDE AT WHICH THE ENERGY DESCENDS SOUTH AND
BREAK OFF AT. THE 12Z NAM CONTINUES ALONG WITH THE 00Z UKMET TO BE
FURTHER WEST AND THEREFORE FASTER TO RETROGRADE... OPPOSED TO THE
00Z ECMWF WHICH IS A BIT SLOWER.  THE GEFS SOLUTIONS HAD SUPPORTED
THE WESTERN NAM/UKMET... BUT THE 06Z BACKED UP CLOSER TO THE 00Z
NAEFS MEAN WHICH WAS AN EXCELLENT MIDDLE GROUND SOLUTION WITHIN
THE 00Z ENSEMBLE CLUSTER PLOT.  LIKEWISE THE 12Z GFS HAS SLOWED A
BIT TOWARD THE ECMWF... THIS PROVIDES SOME INCREASED CONFIDENCE
FURTHER EAST.  AS SUCH WILL FAVOR A 12Z GFS/00Z ECMWF SOLUTION
ALONG WITH THE 06Z GEFS AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
PLEASE REFER TO WPC QPFPFD FOR ADDITIONAL DETAILS REGARDING THE
QPF PREFERENCES GIVEN HIGH IMPACT RAINFALL SITUATION TO EVOLVE IN
SOUTHERN PLAINS SUNDAY-MONDAY.

19Z UPDATE: THE 12Z NON-NCEP TREND WAS TOWARD A MORE PROGRESSIVE
RETROGRADING.  THE 12Z ECMWF HAVING WEAKER MID-TROF ENERGY
DROPPING MORE INTO THE BASE WAS ABLE TO WAVE BREAK A BIT EARLIER
AND FURTHER WEST NOW PROGRESSING FURTHER WEST OF EARLIER
PREFERENCE/12Z GFS.  THIS WAS SUPPORTED BY THE CMC IN PLACEMENT
AND TIMING AND NOT AS FAR SOUTH AS THE 00Z RUN.  THE 12Z UKMET
HOWEVER IS VERY STRONG AND SUPPORTS INJECTING SHORTWAVE ENERGY TO
BREAK INTO A CLOSED LOW OVER AZ ON SAT NIGHT/SUN MORNING ALSO
LEADING TO FURTHER LATITUDINAL DROP TOO MAKING IT A FAST AND
SOUTHWARD LEADER. THE 12Z GEFS CONTINUES TO BE FURTHER WEST THAN
THE GFS...FURTHER SUPPORTING THE TREND.  AS SUCH WILL SUPPORT A
SLIGHT WESTWARD SHIFT AND INCLUDE THE 12Z ECMWF/CMC INTO THE BLEND
WITH THE GEFS/GFS...WITH THIS CHANGE CONFIDENCE IS REDUCED
SLIGHTLY TO JUST AVERAGE.


TROUGHING BECOMING ESTABLISHED IN THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

A SHORTWAVE ON THE SOUTHWESTERN PERIPHERY OF THE DEEPENING LARGER
SCALE GLOBAL CYCLONE IN NORTHEASTERN CANADA SUPPORTS HEIGHT FALLS
ACROSS NEW ENGLAND BEHIND A COLD FRONT/WEAK SURFACE WAVE THAT
SHIFTS OUT OF MAINE THIS AFTERNOON.  EXTREMELY TIGHT MASS FIELD
ALIGNMENT FOR THESE SMALLER FEATURES AS WELL AS THE DEEP LOW IN
CANADA THROUGH THE VAST MAJORITY OF THE FORECAST PERIOD PROVIDES
ABOVE AVERAGE CONFIDENCE IN A GENERAL MODEL BLEND INCLUDING THE
12Z OPERATIONAL GUIDANCE AND 12Z GEFS.


LINGERING MID-LEVEL LOW/JULIA`S REMAINS ACROSS THE SOUTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

REMAINING TROF ALONG THE CAROLINA COAST WILL BE STRETCHED UNDER
INFLUENCE OF DEEPENING TROF ACROSS NEW ENGLAND TODAY THROUGH
SUNDAY WITH THE REMAINING ENERGY SHIFTING SOUTHEAST IN A WEAK
HEIGHT MINIMUM ACROSS GA/FL PANHANDLE.  STRONG ALIGNMENT EXISTS
WITH THE 12Z OPERATIONAL GUIDANCE AS WELL AS THE 12Z GEFS
SUPPORTING A GENERAL MODEL BLEND AT 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...

GALLINA

$$





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