Prognostic Meteorological Discussion
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843
FXUS10 KWNH 260439
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1238 AM EDT SUN MAR 26 2017

VALID MAR 26/0000 UTC THRU MAR 29/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...CLOSED LOW CROSSING THE MID MS/OH VALLEYS SUN...
...SYSTEM WEAKENING INTO THE GREAT LAKES/NORTHEAST THROUGH MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM THROUGH MON AS
IT LIFTS TOWARD THE GREAT LAKES AND NORTHEAST AND GRADUALLY
DAMPENS OUT. A GENERAL MODEL COMPROMISE WILL BE PREFERRED.


...NORTHERN STREAM TROUGH EXITING THE NORTHERN ROCKIES...
...EJECTING ACROSS THE NORTHERN PLAINS/UPPER MIDWEST SUN/MON...
...REACHING THE ONTARIO/QUEBEC BORDER TUES EVENING...
...POSSIBLE SHORTWAVE PHASING OVER NEW ENGLAND BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: BLEND OF THE 12Z UKMET AND 12Z ECENS MEAN
CONFIDENCE: BELOW AVERAGE

THE MODELS ADVERTISE THE NORTHERN STREAM COMPONENT OF A LARGER
SCALE WESTERN U.S. TROUGH EJECTING OUT OF THE NORTHERN ROCKIES AND
ADVANCING PROGRESSIVELY EASTWARD ACROSS SOUTHERN CANADA AND THE
FAR NORTHERN PLAINS/UPPER MIDWEST REGION THROUGH SUN AND MON. BY
LATE TUES...THE ENERGY WILL BE MOVING ACROSS ONTARIO AND QUEBEC
AND POTENTIALLY AMPLIFYING ACROSS NEW ENGLAND BY WED. THE KEY TO A
MORE AMPLIFIED SOLUTION IS THE POTENTIAL FOR SOME SHORTWAVE
PHASING AS REMNANT SOUTHERN STREAM ENERGY LIFTS NORTHEAST ACROSS
THE OH VALLEY/NORTHEAST MON AND TUES. THE 00Z CYCLE OF THE GFS
CONTINUES TO STAND OUT SIGNIFICANTLY AS A DEEPER SOLUTION...WITH A
STRONGER SURFACE LOW EJECTING OUT OF THE OH VALLEY AND MUCH MORE
DEEPENING OVER NEW ENGLAND. THE 00Z NAM TENDS TO SUPPORT A WEAKER
VERSION OF THE GFS...BUT THE 12Z UKMET/12Z CMC AND 12Z ECMWF ARE
ALL FLATTER WITH THE ENERGY WITH LITTLE IF ANY PHASING. THE GFS
DOES HAVE SUPPORT FROM A LARGE NUMBER OF GEFS MEMBERS...BUT THE
EURO AND CANADIAN MEMBERS ARE GENERALLY MUCH FLATTER THAN THE GEFS
MEMBERS. OVERALL THERE IS STRONGER SUPPORT TOWARD THE WEAKER
CAMP...AND AS SUCH WILL MAINTAIN CONTINUITY AND SUPPORT THE WEAKER
CONSENSUS. THE ECMWF IN ITSELF MAY BE A TAD TOO SLOW AND TO FAR
SOUTH WITH THE SURFACE WAVE EJECTING OUT OF THE OH VALLEY AND THEN
OFFSHORE THE NORTHEAST BY WED. SO WILL PREFER A CONSENSUS OF THE
12Z UKMET AND 12Z ECENS MEAN SINCE THERE ARE A NUMBER OF EURO
MEMBERS THAT ARE AT LEAST A LITTLE FASTER AND NORTH OF THE
DETERMINISTIC ECMWF. GIVEN THE LARGE MODEL SPREAD WITH THE LOW
PRESSURE EVOLUTION...CONFIDENCE IS QUITE LIMITED.


...SOUTHERN STREAM UPPER TROUGH CURRENTLY OVER THE FOUR CORNERS...
...ENERGY EJECTING INTO THE CNTRL/SRN PLAINS SUN NIGHT/MON...
...SYSTEM WEAKENING INTO THE OH VALLEY/NORTHEAST MON NIGHT/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECENS MEAN...MIDWAY BETWEEN THE 00Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE...BECOMING BELOW AVERAGE BY END OF PERIOD

THE 00Z GFS OVERALL AGAIN APPEARS TOO FAST HERE GIVEN THE LATEST
ENSEMBLE DISTRIBUTION ALTHOUGH IT HAS TRENDED SLOWER COMPARED TO
EARLIER RUNS. EVENTUALLY THE GFS APPEARS TO BE TOO DEEP WITH ITS
SURFACE LOW THE 12Z CMC IS ANOTHER MODEL THAT STANDS OUT AGAINST
THE OTHERS AND HAS LITTLE TO NO SUPPORT WITH ITS SLOWER/STRONGER
SOLUTION. THE 12Z ECMWF IN TIME BECOMES PERHAPS A BIT TOO SLOW
RELATIVE TO THE MODEL CONSENSUS...ESPECIALLY WITH ITS SURFACE LOW.
MEANWHILE...THE 12Z UKMET IS FASTER THAN THE 12Z ECMWF...AND AT
THE SURFACE EVENTUALLY BECOMES A BIT FASTER THAN EVEN THE GFS.
WILL FAVOR THE 12Z ECENS MEAN AT THIS POINT WHICH ALSO REPRESENTS
A COMPROMISE IN LOW TIMING BETWEEN THE GFS AND ECMWF. CONFIDENCE
IN TIME BECOMES LIMITED GIVEN THE TIMING SPREAD IN THE GUIDANCE
WITH THE SURFACE LOW.


...UPPER TROUGH/COLD FRONT REACHING THE WEST COAST SUN...
...CLOSED LOW EVOLUTION INTO THE SOUTHWEST MON/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE IN GOOD AGREEMENT ON THE DEVELOPMENT OF A RATHER
STRONG UPPER TROUGH AND ASSOCIATED CLOSED LOW OVER THE SOUTHWEST
AND FOUR CORNERS REGION MON AND TUES...WITH THE HEIGHT FALLS
ENCROACHING ON THE SOUTHERN HIGH PLAINS BY WED. THE 00Z NAM AND
12Z CMC TEND TO BE A TAD STRONGER WITH THE HEIGHT FALLS COMPARED
TO THE 00Z GFS/12Z UKMET AND 12Z ECMWF. THE 12Z CMC ALSO BECOMES A
BIT SLOWER THAN THE REMAINING GUIDANCE BY THE END OF THE PERIOD.
BASED ON SOMEWHAT BETTER MODEL CLUSTERING AND ENSEMBLE SUPPORT...A
BLEND OF THE GFS/UKMET AND ECMWF WILL BE PREFERRED WITH THIS
SYSTEM.


...COLD FRONT WEAKENING INTO BRITISH COLUMBIA ON TUE...
...ONSHORE FLOW INTO THE PACIFIC NORTHWEST THROUGH TUE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z NAM/00Z GFS AND 12Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE 12Z CMC AND ESPECIALLY THE THE 12Z UKMET APPEAR TOO AMPLIFIED
WITH THE LOW CENTER APPROACHING BRITISH COLUMBIA BY TUES...WITH
THE REMAINING MODELS AND THE ENSEMBLE MEANS CLUSTERED AROUND A
LESS AMPLIFIED SCENARIO. THE 00Z NAM/00Z GFS AND 12Z ECMWF ARE
CLOSEST TO THE MODEL CONSENSUS AND A BLEND OF THESE SOLUTIONS WILL
BE PREFERRED.


www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

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