Prognostic Meteorological Discussion
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FXUS10 KWNH 270429
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1228 AM EDT SAT AUG 27 2016

VALID AUG 27/0000 UTC THRU AUG 30/1200 UTC

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

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


...LOW LEVEL WAVE EXITING THE LOWER MO VALLEY EARLY SAT...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM TENDS TO HANG ONTO A SOMEWHAT STRONGER SURFACE LOW
THAT LIFTS OUT OF THE LOWER MO VALLEY EARLY SAT AND CROSSES THE
UPPER GREAT LAKES REGION THROUGH THE DAY. VERY GOOD MASS FIELD
AGREEMENT SEEN OTHERWISE...AND SO A NON-NAM CONSENSUS WILL BE
PREFERRED.


...UPPER TROUGH CROSSING NORTHERN PLAINS/UPPER MIDWEST ON SAT...
...ENERGY CROSSING OVER TO NEW ENGLAND ON MON...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM IS A STRONGER AND SOMEWHAT FASTER OUTLIER WITH THIS
SYSTEM. THE REMAINING GUIDANCE SHOWS GOOD AGREEMENT AND SO A
NON-NAM CONSENSUS WILL BE PREFERRED WITH THIS TOO.


...UPPER TROUGH DROPPING SOUTH THROUGH BRITISH COLUMBIA ON SAT...
...ENERGY CROSSING SOUTHERN CANADA SUN/MON...
...COLD FRONT MOVING THROUGH THE NORTHERN PLAINS/UPPER MIDWEST
SUN/MON...

PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z CMC REMAINS A BIT DEEPER AND SLOW WITH THIS SYSTEM
COMPARED TO THE REMAINING GUIDANCE. THE 00Z NAM ALSO IS A BIT DEEP
WITH THE UPPER TROUGH...BUT IS NOTABLY SLOW WITH ITS COLD FRONT
THAT CROSSES SOUTHERN CANADA AND THE NORTHERN PLAINS. BETTER MODEL
CLUSTERING RESIDES WITH THE 00Z GFS/12Z UKMET AND 12Z ECMWF WHICH
AGAIN TENDS TO HAVE BETTER ENSEMBLE SUPPORT AS WELL.


...UPPER TROUGH DIGGING SOUTH OFFSHORE BRITISH COLUMBIA BY MON...

PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF
CONFIDENCE: AVERAGE

THE 00Z NAM REMAINS A BIT FASTER THAN THE MULTI-MODEL CONSENSUS IN
BRINGING THIS NEXT UPPER TROUGH OFFSHORE BRITISH COLUMBIA AND
APPROACHING THE PACIFIC NORTHWEST. THE STRONGER MODEL CLUSTERING
RESIDES WITH THE 00Z GFS/12Z UKMET AND 12Z ECMWF...AND A BLEND OF
THESE SOLUTIONS WILL BE PREFERRED.


...WEAK MID LEVEL TROUGH OVER THE SOUTHWEST THIS WEEKEND...

PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF
CONFIDENCE: ABOVE AVERAGE

WHILE THERE IS BROAD AGREEMENT WITH THE EVOLUTION OF THIS
FEATURE...THE 00Z NAM AND EVENTUALLY THE 12Z CMC APPEAR TO BE A
LITTLE TOO STRONG. THE 12Z UKMET IS PERHAPS JUST A TAD TOO
WEAK...AND SO BASED ON THIS...A BLEND OF THE 00Z GFS AND 12Z ECMWF
WILL AGAIN BE PREFERRED.


...LOW PRESSURE APPROACHING SOUTH FL AND THE KEYS BY SUN...

PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF
CONFIDENCE: BELOW AVERAGE

THE MODELS CONTINUE TO STRUGGLE WITH THE EVOLUTION OF 99L MOVING
WEST-NORTHWEST IN BETWEEN THE NORTH COAST OF CUBA AND THE
BAHAMAS...AND TOWARD THE GENERAL VICINITY OF SOUTH FL AND THE FL
KEYS. THE 00Z NAM BECOMES THE SLOWEST SOLUTION AND ALSO SHOWS A
BIT MORE DEVELOPMENT THAN THE MODEL CONSENSUS AS THE SYSTEM MOVES
INTO THE EASTERN GULF OF MEXICO. THE GLOBAL MODELS ARE ALL FASTER
AND FARTHER WEST...BUT THE 12Z CMC APPEARS TO BE TOO PROGRESSIVE.
OVERALL...THE 00Z GFS/12Z UKMET AND 12Z ECMWF CLUSTER IN BETWEEN
THE NAM AND CMC...BUT THE UKMET IS THE STRONGER OF THESE
SOLUTIONS...WITH THE GFS AND ECMWF BOTH RATHER WEAK. THERE ARE
SOME TIMING DIFFERENCES NOTED WITH THE GFS STILL A BIT FASTER THAN
THE ECMWF AS WELL. THERE IS SIGNIFICANT ENSEMBLE MEMBER SPREAD
WITH 99L...AND SO CONFIDENCE IS LIMITED. FOR NOW...WILL ATTEMPT TO
TAKE A CONSENSUS OF THE WEAKER GFS/ECMWF SOLUTIONS GIVEN THE
CURRENT LEVEL OF DISORGANIZATION TO THE SYSTEM.


...WEAK MID LEVEL LOW CENTER NEAR THE WESTERN GULF COAST ON
SAT/SUN...

PREFERENCE: NON-CMC CONSENSUS
CONFIDENCE: AVERAGE

THE 12Z UKMET REMAINS QUITE A BIT STRONGER WITH THIS FEATURE...BUT
LACKS DETERMINISTIC SUPPORT FROM THE OTHER MODELS. THE LATEST GEFS
MEAN AND ECENS MEAN SUPPORT A WEAKER/FLATTER SYSTEM AT LEAST FOR
MASS FIELDS. WILL THUS LEAN TOWARD A NON-CMC CONSENSUS AT THIS
TIME.

ORRISON

...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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