Prognostic Meteorological Discussion
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000
FXUS10 KWNH 281655
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1254 PM EDT FRI AUG 28 2015

VALID AUG 28/1200 UTC THRU SEP 01/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


...SHORTWAVE TROUGH MOVING THROUGH THE MIDWEST/GREAT LAKES
REGION...

PREFERENCE: NON-ECMWF CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 00Z ECMWF IS A DEEPER OUTLIER SOLUTION WITH THIS SYSTEM AS IT
MOVES INTO THE GREAT LAKES REGION. DESPITE THE FACT THAT THE 00Z
ECENS MEAN FAVORS THE DETERMINISTIC ECMWF...THE REMAINING NON-NCEP
SOLUTIONS INCLUDING THE 00Z CMC AND 00Z UKMET ARE WEAKER/FLATTER.
THE 06Z GEFS MEAN...12Z GFS AND TO AN EXTENT THE 12Z NAM ALSO
FAVOR THE WEAKER SCENARIO. SO WILL PREFER A NON-ECMWF CONSENSUS AT
THIS POINT.


...UPPER TROUGH OVER THE GULF OF MEXICO...

PREFERENCE: BLEND OF THE 06Z GEFS MEAN AND 00Z ECENS MEAN
CONFIDENCE: BELOW AVERAGE

THE UPPER TROUGH OVER THE GULF OF MEXICO WILL BE MOVING WEST OVER
THE NEXT COUPLE OF DAYS BEFORE GENERALLY STALLING. THE GUIDANCE
REFLECTS SOME COMPLICATED EVOLUTION OF THIS THOUGH. ALL OF THE
MODELS SHOW ENERGY EJECTING OUT OF THE BASE OF THE TROUGH INTO THE
SOUTHEAST U.S. SAT AND SUN WHILE THE OVERALL TROUGH AXIS SLOWLY
SHIFTS WEST. BY MON...THERE IS SPREAD WITH HOW THE VORTICITY IS
ORIENTED WITHIN THE TROUGH. MOST OF THE MODELS SHOW THE TROUGH
ELONGATING FROM THE WESTERN GULF OF MEXICO NORTHWARD INTO THE
LOWER/MID MS VALLEY. THE 12Z NAM TENDS TO BE STRONGER WITH THE
TROUGH...WITH THE 00Z UKMET AND 00Z CMC WEAKER. THE 12Z GFS AND
00Z ECMWF SPLIT THE DIFFERENCE...BUT THE GFS HAS STRONGER ENERGY
FOCUSED OVER PORTIONS OF OK/TX/LA WHERE THERE IS INTERACTION
BETWEEN A CONVECTIVE VORT THAT DROPS SOUTH FROM THE MIDWEST AND
VORT ENERGY OVER THE NORTHWEST GULF OF MEXICO. AT THIS POINT...IT
IS DIFFICULT TO PICK ANY ONE SOLUTION...SO WILL LEAN TOWARD THE
ENSEMBLE MEANS WITH A BLEND OF THE 06Z GEFS MEAN AND 00Z ECENS
MEAN.


...SHORTWAVE TROUGHS CROSSING THE PACIFIC NORTHWEST THIS WEEKEND...

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

THE 00Z UKMET AND 00Z CMC ARE FASTER THAN THE 12Z NAM/12Z GFS AND
00Z ECMWF WITH THE SHORTWAVE TROUGH AND ASSOCIATED SURFACE LOW
THAT MOVES INTO THE PACIFIC NORTHWEST TONIGHT AND SAT. THIS ENERGY
SHEARS INLAND AHEAD OF ADDITIONAL STRONG HEIGHT FALLS DIGGING
SOUTH FROM THE GULF OF AK AND THROUGH BRITISH COLUMBIA. THIS WILL
COME IN THE FORM OF MULTIPLE SHORTWAVE IMPULSES...AND BY THE END
OF THE PERIOD A BROAD BUT RELATIVELY DEEP TROUGH WILL BE IMPACTING
THE NORTHWEST AND WESTERN CANADA. THE STRONGEST MODEL CLUSTERING
INVOLVES THE 12Z GFS AND 00Z ECMWF...AND A BLEND OF THESE
SOLUTIONS WILL BE PREFERRED.


...TROPICAL STORM ERICA...

THE LATEST NHC FORECAST TRACK IS CLOSE TO THE GLOBAL MODEL
CONSENSUS THROUGH ABOUT 48 HRS...BUT THEREAFTER THE 12Z GFS/00Z
ECMWF AND 00Z UKMET ALL TRACK ERICA LEFT OF THE NHC TRACK. THE 12Z
NAM AND 00Z CMC THEN TREND FASTER AND TO THE RIGHT OF THE NHC
TRACK. PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY/DISCUSSION
FOR MORE INFORMATION ON ERICA.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$




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