Prognostic Meteorological Discussion
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000
FXUS10 KWNH 310648
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 AM EDT SUN JUL 31 2016

VALID JUL 31/0000 UTC THRU AUG 03/1200 UTC

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

00Z GUIDANCE EVALUATION INCLUDING PREFERENCE AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SLOW-MOVING LONGWAVE TROUGH TRACKING FROM THE MS RIVER VALLEY
TOWARD NEW ENGLAND WITH SFC LOW PRESSURE FORMING OFF SOUTHERN NEW
ENGLAND LATE MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE BROAD TROF CROSSING THE GREAT LAKES/OHIO VALLEY CONTINUES ITS
EASTWARD TREK TO THE EAST COAST UNDER FAIRLY GOOD AGREEMENT WITH
THE ONLY EXCEPTION CONTINUING TO BE THE NAM.  THE 00Z NAM RUN
CONTINUES TO DRAW A MORE AMPLIFIED WAVE OUT OF QUEBEC LEADING TO
FASTER HEIGHT FALLS ACROSS E NEW ENGLAND LEADING TO A
FORWARD/FASTER AND STRONGER SURFACE REFLECTION E OF THE GULF OF
MAIN WHICH BEING DEEPER TURNS NORTHWARD TOWARD CAPE RACE WELL OFF
THE WELL ORIENTED SURFACE BOUNDARY SEEN IN THE REST OF THE
GUIDANCE SUITE.   THOUGH THERE REMAIN SMALL DIFFERENCES WITH THE
REST OF THE GUIDANCE SUITE IN EXACT POSITIONING ALONG THE FRONT IS
WELL ALIGNED GIVEN ITS STRENGTH.  AS SUCH WILL CONTINUE TO FAVOR A
NON-NAM BLEND SOLUTION AS SLIGHTLY ABOVE AVERAGE CONFIDENCE.

07Z UPDATE: LITTLE CHANGE FOR THE 00Z CMC/ECMWF TO KEEP IN LINE
WITH THE EARLIER PREFERENCE NEAR THE 00Z GFS (AND NOW 00Z GEFS);
THOUGH THE 00Z UKMET HAS SOME COASTAL DEVELOPMENT FEEDBACK NEAR
THE HUDSON CANYON VICINITY  THAT RESULTS IN A WRAPPED UP/DEEPER
SLOWER SOLUTION WHICH SEEMS UNLIKELY.  AS SUCH WILL KEEP WITH
CONTINUITY A SUPPORT A 00Z GFS/ECMWF/CMC BLEND AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.


CLOSED LOW MOVING ACROSS WESTERN/CENTRAL CANADA WITH DEEP SURFACE
CYCLONE AND COLD FRONT TRACKING ACROSS THE NORTHERN TIER.  DRAWING
MID-LEVEL SHEAR AXIS AND ASSOCIATED SURFACE WAVE OUT OF THE
CENTRAL ROCKIES INTO THE PLAINS MON/TUES AND GREAT LAKES BY WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/CMC BLEND
CONFIDENCE: AVERAGE

CLOSED LOW ACROSS SW CANADA WILL CONTINUE TO TRACK ACROSS THE
SOUTHERN ROCKIES DEVELOPING A SURFACE LOW THAT RAPIDLY DEVELOPS
ACROSS SE ALBERTA/SW SASKATCHEWAN WITH DRAPED COLD FRONT ACROSS
MT.  THIS DRAWS ENERGY OUT OF THE SW RIDGE AS A SHEAR AXIS
SUPPORTING A SURFACE CYCLONE ACROSS THE BLACK HILLS BY MONDAY
MORNING...FOR THE MOST PART MODELS AND ENSEMBLES ARE ALIGNED AT
THIS POINT...THEREAFTER...THE SPREAD STARTS TO INCREASE STEADILY
WITH TWO GENERAL CAMPS.

THE FIRST IS SUPPORTED BY THE 12Z UKMET AND 00Z GFS BOTH
EMPHASIZING STRONGER SHORTWAVE ENERGY ACROSS WY INTO THE NORTHERN
PLAINS.  AS THE MAIN UPPER LOW SHEARS ACROSS CENTRAL CANADA AND
THE SURFACE LOW OCCLUDES...THE FASTER/STRONGER NORTHERN SOLUTION
DRAWS THE MAIN UPPER LOW EAST IN CANADA/ N MN WHILE ALSO
SUPPORTING A SLOWER DEEPER FRONTAL ZONE ACROSS THE UPPER MS
VALLEY.  IN OPPOSITION; THE 12Z ECMWF IS FURTHER NORTH AND
DISPLACED FROM THE ROCKIES ENERGY ALLOWING FOR A FASTER EASTWARD
PROGRESSION OF THE FRONTAL ZONE INTO THE SOUTHERN GREAT LAKES BY
WED MORNING; THIS IS SUPPORTED IN THE US BY A STRONGER CMC.  THE
00Z NAM SPLITS THE DIFFERENCE BETWEEN THE SOLUTIONS...BEING
SLOWER/NORTHWEST ACROSS CANADA WHILE ON PACE WITH THE GFS WITH THE
FRONT ACROSS THE UPPER MS RIVER VALLEY INTO THE CENTRAL GREAT
PLAINS BY WED...HOWEVER ITS TYPICAL BIAS OF OVER DEVELOPING THE
SHORTWAVE ENERGY ACROSS THE CENTRAL ROCKIES MAKES IT QUESTIONABLE
FOR FULL BLENDING.   INTERESTINGLY...THE GFS/ECMWF  APPEAR TO BE
ON THE OUTER FRINGES OF THEIR ENSEMBLE SUITES AS WELL AS AWAY FROM
A COMMON SOLUTION.  SUCH THE 21Z SREF/18Z GEFS AND 12Z ECENS MEAN
ARE MUCH BETTER ALIGNED OVERALL WITH A MORE CENTRAL SOLUTION.  ALL
CONSIDERED WILL FAVOR THESE ENSEMBLE MEANS (SREF/GEFS/ECENS
MEAN)...BUT WITH LITTLE/NO DETERMINISTIC REPRESENTATION TO
BLEND...A GFS/ECMWF BLEND MAY SUFFICE IF THE MEANS ARE NOT
AVAILABLE FOR YOUR BLEND.  GIVEN THE SPREAD IS HIGH FOR THIS TIME
OF YEAR... CONFIDENCE IS LOWER THAN NORMAL PARTICULARLY OVER
CANADA/NORTHERN FRINGES OF US WHERE IT IS GREATEST.

07Z UPDATE: THE 00Z ECMWF (SUPPORTED BY STRONG AGREEMENT OF THE
00Z CMC) TRENDED TOWARD THE COMMON SOLUTION TOWARD THE INITIAL
PREFERENCES.  THE 00Z UKMET APPEARS TO HAVE INCREASED A STRONGER
SOLUTION ACROSS THE NORTHERN TIER OF THE US...INCREASING
SOUTHEASTWARD SHIFT OF THE UPPER LOW/SURFACE SOLUTION ACROSS
CANADA; WHILE THE FRONTAL ZONE IS ONLY A BIT FASTER ACROSS THE
GREAT LAKES THAN THE REST OF THE CONSENSUS...IT SEEMS WELL
DEPARTED FROM THE REST OF THE GUIDANCE IN CANADA TO NOT HAVE
SURROUNDING AFFECTS ELSEWHERE IN THE STATES.

ALONG WITH THE GFS (STRENGTHENED BY GOOD PACKING WITHIN THE 00Z
GEFS SOLUTION NEAR IT) CAN NOW SUPPORT USING DETERMINISTIC MODELS
TO BEST REPRESENT THE ENSEMBLES...IN A GFS/ECMWF/CMC BLEND (WITH
INCLUSION OF THE SREF/GEFS AND ECENS MEAN IF DESIRED TO STRENGTHEN
THE BLEND) AT AVERAGE CONFIDENCE.


TRAILING CLOSED LOW MOVING THROUGH PACIFIC NORTHWEST TUES INTO
NORTHERN US ROCKIES BY WED
WITH SURFACE CYCLOGENESIS IN CENTRAL MT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

AS THE INITIAL CLOSED LOW EJECTS ACROSS THE SOUTHERN CANADIAN
PRAIRIES...THE TRAILING SECOND CLOSED LOW APPROACHES THE PACIFIC
NORTHWEST COAST LATE MON INTO TUES.  THE MODELS CONTINUE TO BE
MUCH STRONGER IN AGREEMENT WITH SHAPE/PLACEMENT AND TIMING WITH
RESPECT TO THIS LOW.  EVENTUALLY THE 12Z UKMET LATE TUES/EARLY WED
IS A BIT STRONGER/MORE CONSOLIDATED AND STARTS TO LAG THE VERY
TIGHT CLUSTER EVER SO SLIGHTLY.  THIS DELAY IS ALSO MANIFESTED BY
THE LEE CYCLOGENESIS ACROSS MT ON WED BEING A BIT WEST OF THE BEST
CLUSTER OF THE GFS/CMC/ECMWF AND GEFS/CMCE/ECENS MEAN.  THE 00Z
NAM THOUGH ALIGNED ALOFT WAS A BIT FURTHER NORTH FOR THE SURFACE
LOW.   THOUGH INCLUSION OF THE UKMET OR NAM MAY BE WARRANTED WILL
GO WITH A MUCH HIGHER CONFIDENCE IN THE 00Z GFS AND 12Z CMC/ECMWF
BLEND.

07Z UPDATE: THE 00Z UKMET TRENDED FASTER TO JOIN THE TIGHT PACKING
OF SOLUTIONS (INCLUDING THE NEW 00Z CMC/ECMWF WHICH SHOWED LITTLE
CHANGE).  GIVEN ONLY SMALL DIFFERENCE AT 12Z ON WED AT THE SURFACE
AS WELL AS ALL THE DOWNSTREAM SPREAD...SHOULD JUSTIFY INCLUSION OF
THE NAM AS WELL INTO AN OPERATIONAL MODEL BLEND AT ABOVE AVERAGE
CONFIDENCE.

GALLINA


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

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

$$




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