Prognostic Meteorological Discussion
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000
FXUS10 KWNH 260459
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1258 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/GFS/UKMET/CMC AND ECMWF
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...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...
...WEAKER NORTHERN STREAM TROUGH OVER THE NORTHWEST MON/TUES...
...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 WITH THE INITIAL ARRIVAL OF AN
UPPER TROUGH AND COLD FRONT ACROSS THE WEST COAST ON SUN.
HOWEVER...ON MON AND TUES...THE ARE IN VERY GOOD AGREEMENT WITH
THE DEVELOPMENT OF A RATHER STRONG UPPER TROUGH AND ASSOCIATED
CLOSED LOW THAT WILL DROP DOWN THROUGH THE SOUTHWEST AND INTO THE
FOUR CORNERS REGION. THE HEIGHT FALLS WILL BE ENCROACHING ON THE
SOUTHERN HIGH PLAINS BY WED. MEANWHILE...THE MODELS SHOW A WEAKER
NORTHERN STREAM COMPONENT OF THE ORIGINAL TROUGH CROSSING THE
NORTHWEST U.S. AND EJECTING OUT INTO THE NORTHERN HIGH PLAINS BY
TUES AND WED.

THE 00Z NAM AND 12Z CMC TEND TO BE A TAD STRONGER WITH THE
SOUTHERN STREAM 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. FARTHER
NORTH...SOMEWHAT STRONGER MODEL CLUSTERING ALSO EXISTS WITH THE
GFS/UKMET AND ECMWF. THEREFORE...COLLECTIVELY BASED ON BETTER
MODEL CLUSTERING AND ENSEMBLE SUPPORT...A BLEND OF THE GFS/UKMET
AND ECMWF WILL BE PREFERRED WITH THE NORTHERN AND SOUTHERN STREAM
COMPONENTS OF 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.


...SHORTWAVE/SURFACE LOW NEAR THE PACIFIC NORTHWEST BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS CONSENSUS...WEIGHTED TOWARD 12Z UKMET/12Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS HAVE A SHORTWAVE AND ASSOCIATED WEAK SURFACE LOW/FRONT
ARRIVING ACROSS THE PACIFIC NORTHWEST ON WED WITH A PARTICULAR
FOCUS ON THE OLYMPIC PENINSULA. THE 00Z GFS IS A STRONGER OUTLIER
WITH THIS SYSTEM...AND SHOWS STRONGER ONSHORE FLOW IMPACTING THE
OLYMPIC PENINSULA COMPARED TO ANY OTHER MODEL. GENERALLY THE
BETTER MASS FIELD CLUSTERING RESIDES WITH THE 12Z UKMET AND 12Z
ECMWF...SO A NON-GFS CONSENSUS WILL BE PREFERRED BUT WITH MORE
WEIGHTING TOWARD THE UKMET/ECMWF SOLUTIONS.

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

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

ORRISON

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