Prognostic Meteorological Discussion
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000
FXUS10 KWNH 251650
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1249 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 NAM/GFS EVALUATION...INCLUDING PRELIMINARY 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 AND 00Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE 00Z ECMWF HAS TRENDED WEAKER WITH THE UPPER TROUGH ACROSS THE
N-CNTRL U.S. SAT EVENING COMPARED TO ITS RUN FROM 24 HRS
PRIOR...AND IS WEAKER WITH THE MID-LEVEL REFLECTION COMPARED TO
THE 12Z GFS...WITH THE GFS ON THE STRONGER SIDE OF THE
DETERMINISTIC MODELS. GIVEN THE NAM IS ON THE STRONGER SIDE OF THE
GUIDANCE...PERHAPS DUE TO ITS STRONGER SYSTEM EMANATING FROM THE
PLAINS. THE 00Z UKMET IS FLATTER/FASTER WITH THE SYSTEM. A BLEND
OF THE 12Z GFS AND 00Z ECMWF 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...00Z UKMET AND 00Z 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 3 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...00Z UKMET AND 00Z ECMWF.


WEAK MID LEVEL TROUGH OVER THE SOUTHWEST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 12Z GFS
CONFIDENCE: 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.


LOW PRESSURE APPROACHING SOUTH FLORIDA BY SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z ECMWF / O0Z ECMWF MEAN
CONFIDENCE: BELOW AVERAGE

THE 12Z GFS CONTINUES TO BE WEAKER WITH THIS SYSTEM...WHILE THE
ECMWF HAS BEEN CONSISTENTLY ON THE STRONGER SIDE OF THE MODEL
SPREAD. POSITION-WISE...THE 12Z NAM AND 00Z CMC ARE TOWARD THE NRN
EDGE OF A MAJORITY OF THE 00Z ECMWF/GEFS/CMC ENSEMBLE MEMBERS BY
SUN NEAR FLORIDA. GIVEN THE ECMWF IS TOWARD THE STRONGER SIDE OF
THE MODEL GUIDANCE...AND THE GFS REMAINS CONSISTENTLY WEAK...THE
PREFERENCE IS TO BLEND THE ECMWF AND ITS MEAN FROM 00Z TO KEEP THE
FAVORABLE ECMWF POSITION BUT TEMPER ITS STRENGTH DOWNWARD A BIT.


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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