Prognostic Meteorological Discussion
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FXUS10 KWNH 301850
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 PM EDT SUN AUG 30 2015

VALID AUG 30/1200 UTC THRU SEP 03/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF


...SHORTWAVE/ASSOCIATED FRONT SKIRTING NORTHERN NEW ENGLAND EARLY
MON...

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE UPPER FLOW GRADUALLY BEGINS TO AMPLIFY OVER EASTERN CANADA BY
EARLY NEXT WEEK. MODELS EXHIBIT SOME VARIATION IN TIMING ALTHOUGH
THE BIGGER DIFFERENCE IS WITH REGARD TO THE AMPLITUDE. THE 12Z
UKMET SHOWS A TAD MORE AMPLIFICATION WITH A TROUGH DIGGING ACROSS
THE REGION VERSUS THE GLOBAL MODEL CONSENSUS. A NON-UKMET
CONSENSUS WILL BE PREFERRED.


...SHORTWAVE LIFTING THROUGH THE SOUTHEAST TO THE MID-ATLANTIC...
...RETROGRADING ENERGY FOCUSING FROM THE SOUTHERN PLAINS TO THE OH
VALLEY...

PREFERENCE: BLEND OF THE 12Z GEFS MEAN AND 00Z ECENS MEAN
CONFIDENCE: SLIGHTLY BELOW AVERAGE

WATER VAPOR IMAGERY SHOWS A POTENT UPPER LOW CROSSING INTO EXTREME
SOUTHERN AL WHICH WILL SLOWLY OPEN UP INTO A TROUGH AXIS THAT
PIVOTS THROUGH THE INTERIOR SOUTHEAST AND INTO THE MID-ATLANTIC
REGION THROUGH MON. THERE IS A GENERAL CONSENSUS THAT THE SYSTEM
WILL LIFT NORTH AND EAST TOWARD THE LOWER MID-ATLANTIC DURING THE
NEXT 24 TO 36 HOURS. THE STRONGER MODEL CLUSTERING FAVORS A BLEND
OF THE 12Z GFS AND 12Z ECMWF...WITH THE 12Z UKMET APPEARING A
LITTLE TOO WEAK AND PROGRESSIVE...AND THE 12Z CMC A BIT SLOW. THE
12Z NAM DOES LEND SUPPORT FOR THE GFS/ECMWF CAMP.

MEANWHILE...TO THE WEST...A SEPARATE WEAKNESS IN THE FLOW WILL
ELONGATE FROM THE SOUTHERN PLAINS NORTHEAST TO THE OH VALLEY WHICH
WILL IN PART BE ENHANCED BY SHORTWAVE ENERGY CURRENTLY DROPPING
SOUTH ACROSS THE MID MS VALLEY. THERE ARE SOME PLACEMENT
DIFFERENCES WITH THE INDIVIDUAL VORT CENTERS AND ESPECIALLY OVER
THE OH VALLEY. THE 12Z NAM AND 12Z CMC HAVE A SLOWER ADVANCE OF
ENERGY EAST THROUGH THE OH VALLEY...WHEREAS THE 12Z ECMWF AND 12Z
UKMET ARE A BIT MORE PROGRESSIVE AND BRING ANOTHER BATCH OF ENERGY
INTO THE MID-ATLANTIC REGION BY WED. THE 12Z GFS IS COMPARABLE TO
THE ECMWF/UKMET TIMING BUT IS A LITTLE SLOWER AND WEAKER. FARTHER
SOUTHWEST...THE 12Z NAM GRADUALLY BECOMES A BIT OF A DEEPER
OUTLIER WITH ENERGY OVER THE SOUTHERN PLAINS AND LOWER MS VALLEY
REGION BY THE END OF THE PERIOD. THE 12Z GFS AND 12Z ECMWF SHOW
BETTER CLUSTERING HERE. BASED ON ALL OF THIS...WILL PREFER TO
REMAIN CLOSE TO THE ENSEMBLE MEANS...AND PREFER A BLEND OF THE 12Z
GEFS MEAN AND 00Z ECENS MEAN WHICH ARE REASONABLY CLOSE TO EACH
OTHER.


...UPPER TROUGH ACROSS THE NORTHWESTERN U.S...

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: AVERAGE

A SERIES OF SHORTWAVES TRACKING THROUGH THE PACIFIC NORTHWEST AND
ADJACENT LOCATIONS DOWNSTREAM WILL HELP MAINTAIN A
PERSISTENT/ANOMALOUS LONGWAVE TROUGH ACROSS THE REGION THROUGH THE
MIDDLE OF NEXT WEEK. THE 12Z UKMET IS A BIT SLOWER IN EJECTING A
SHORTWAVE TOWARD SOUTHERN SASKATCHEWAN ON MON. UPSTREAM THE MODELS
SHOW GOOD AGREEMENT ON THE LARGER SCALE EVOLUTION OF THE HEIGHT
FALLS...AND SO A NON-UKMET CONSENSUS WILL BE PREFERRED.


...REMNANTS OF ERIKA...

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

THE 12Z NAM/12Z UKMET AND 12Z CMC INSIST ON THE REMNANTS OF FORMER
T.S. ERIKA REGENERATING INTO A CLOSED LOW CENTER OVER THE EASTERN
GULF OF MEXICO AND LIFTING NORTH-NORTHEAST INTO NORTHERN FL
THROUGH MON. THE 12Z GFS ALSO FAVORS A WEAK CIRCULATION...BUT THE
12Z ECMWF MAINTAINS A WAVE AXIS. MOST OF THE MODELS ARE ALSO
FAVORING A LOW CENTER EVOLVING OFF THE SOUTHEAST COAST TUES AND
WED WHICH IN PART MAY BE RELATED TO SOME OF THE REMNANTS OF ERIKA.
STRONGER MODEL CLUSTERING OFF THE SOUTHEAST COAST TENDS TO FAVOR A
BLEND OF THE 12Z GFS AND 12Z ECMWF...AND A BLEND OF THESE
SOLUTIONS WILL BE PREFERRED. PLEASE CONSULT THE LATEST NHC
TROPICAL WEATHER OUTLOOK FOR MORE INFORMATION ON THE REMNANTS OF
ERIKA.


...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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