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677
FXUS10 KWNH 251907
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
307 PM EDT THU AUG 25 2016

VALID AUG 25/1200 UTC THRU AUG 29/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


MID LEVEL TROUGH CLIPPING THE NORTHERN PLAINS/UPPER MS VALLEY
ENERGY LIFTING ACROSS ONTARIO/QUEBEC THROUGH FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


WEAKENING MID LEVEL TROUGH EJECTING OUT INTO THE CNTRL PLAINS TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z NAM STANDS OUT FROM THE REMAINING MODEL CONSENSUS WITH A
STRONGER 700-500 MB REFLECTION OF THIS TROUGH ON FRI ACROSS THE
PLAINS. GIVEN A LACK OF SUPPORT FOR THE NAM...RECOMMEND GOING
AGAINST IT.


UPPER TROUGH CROSSING THE NORTHERN ROCKIES TODAY
ENERGY REACHING THE NORTHERN PLAINS/UPPER MIDWEST SAT/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/ECMWF/UKMET
CONFIDENCE: AVERAGE

THE 12Z ECMWF AND UKMET HAVE TRENDED TOWARD THE 12Z GFS WITH THE
UPPER TROUGH ACROSS THE N-CNTRL U.S. SAT EVENING COMPARED TO THEIR
RUNS FROM 12-24 HRS PRIOR. THE GFS REMAINS ON THE STRONGER SIDE OF
THE DETERMINISTIC MODELS BUT NOT TO THE EXTENT OF THE MUCH
STRONGER NAM...PERHAPS DUE TO THE 12Z NAM SYSTEM EMANATING FROM
THE PLAINS. A BLEND OF THE 12Z GFS/ECMWF/UKMET REPRESENTS THE
CLOSEST MATCH TO THE AGREEABLE GEFS/EC MEANS.


UPPER TROUGH DROPPING SOUTH THROUGH BRITISH COLUMBIA ON SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM...12Z UKMET AND 12Z ECMWF
CONFIDENCE: BELOW AVERAGE

THE 12Z GFS IS WEST OF THE DETERMINISTIC CONSENSUS AS THE WAVE
DROPS SOUTH THROUGH BRITISH COLUMBIA...AND ENDS UP FLATTER WITH
THE UPPER TROUGH INTO SWRN CANADA BY SUN MORNING. THE GFS HAS HAD
GOOD RUN TO RUN CONSISTENCY...BUT THE ECMWF HAS TRENDED AWAY FROM
THE GFS OVER ITS PAST 4 RUNS. ENSEMBLE SPAGHETTI HEIGHT CONTOURS
SUGGEST THE GFS IS TOO FLAT...BUT DO NOT OFFER MUCH MORE HELP THAN
THAT GIVEN THE SIZABLE SPREAD. THE GEFS MEAN SUPPORTS THE GFS AND
THE EC MEAN SUPPORTS THE ECMWF. SINCE THERE IS NO CLEAR
DIRECTION...WILL GO TOWARD THE BETTER CONSENSUS LED BY THE 12Z
NAM/UKMET/ECMWF.


WEAK MID LEVEL TROUGH OVER THE SOUTHWEST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/ECMWF/UKMET
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE 12Z NAM/GFS ARE SLOWER TO MOVE THE UPPER TROUGH EASTWARD
ACROSS THE FOUR CORNERS REGION WHILE THE 00Z ECMWF/UKMET/CMC ARE
FASTER...OR AT LEAST FASTER WITH A PORTION OF THE ENERGY WHILE
HOLDING SOME BACK TOWARD THE SOUTHWEST. ENSEMBLE SPAGHETTI HEIGHTS
SHOW THE STRONGER NAM TO BE IN THE MINORITY BUT GIVE NO CLEAR
INDICATION OF WHICH WAY TO LEAN. GIVEN THE WEAK FLOW IN PLACE
ACROSS THE SOUTHWEST...WILL TEND TO FAVOR SLOWER MOVEMENT AS
ADVERTISED BY THE 12Z GFS.

19Z UPDATE -- THE 12Z ECMWF AND UKMET HAVE ADJUSTED TOWARD THE
GFS...INCREASING CONFIDENCE TOWARD A SLOWER TRACK. A BLEND OF THE
GFS/ECMWF/UKMET AFFORDS A DECENT COMPROMISE...WHILE THE 12Z CMC
REMAINS MORE PROGRESSIVE.


LOW PRESSURE APPROACHING SOUTH FLORIDA BY SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET
CONFIDENCE: BELOW AVERAGE

WHILE THE 12Z GFS CONTINUES TO BE WEAKER WITH THIS SYSTEM...THE
ECMWF HAS ALSO ADJUSTED WEAKER WITH TODAYS 12Z RUN AFTER BEING
CONSISTENTLY ON THE STRONGER SIDE OF THE MODEL SPREAD.
POSITION-WISE...THE 12Z NAM AND 12Z CMC ARE TOWARD THE NRN AND WRN
EDGE...RESPECTIVELY...OF A MAJORITY OF THE 00Z ECMWF/GEFS/CMC
ENSEMBLE MEMBERS BY SUN NEAR FLORIDA. GIVEN THE ADJUSTMENT FROM
THE 12Z ECMWF/UKMET/CMC TO A WEAKER SURFACE LOW...THERE IS GROWING
CONSENSUS FOR A SYSTEM WITH LESS STRENGTH THAN DEPICTED IN EARLIER
SOLUTIONS. THE PREFERENCE IS TO BLEND THE SIMILAR ECMWF AND
UKMET...WHICH IS CLOSE TO THE PREVIOUS PREFERENCE FOR A 00Z
ECMWF/ECMWF MEAN BLEND.


OTTO

...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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