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FXUS10 KWNH 301837
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 PM EDT SAT AUG 30 2014

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

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

...AN EVALUATION OF THE 12Z CMC/UKMET/ECMWF ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...UPPER-LEVEL ENERGY LIFTING FROM THE LOWER MS VALLEY UP TOWARD
THE OH VALLEY...

FINAL PREFERENCE: 12Z GFS/ECMWF/CMC ARE USEFUL
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AN UPPER LOW WHICH IS ALONG THE WESTERN GULF COAST HAS BEEN
RESPONSIBLE FOR VERY HEAVY RAINFALL THIS MORNING ACROSS LA. AS THE
SYSTEM LIFTS NORTH AND EAST...IT WILL GRADUALLY SHEAR AS IT MOVES
THROUGH THE TN VALLEY AND EVENTUALLY INTO THE CENTRAL
APPALACHIANS. IT APPEARS SOME ENERGY WILL LINGER BACK ALONG THE
WESTERN GULF COAST WHILE IN MORE OF A SHEARED STATE. OVERALL...THE
12Z NAM/UKMET SHOW TWO DISTINCT WAVES MOVING THROUGH THE CENTRAL
APPALACHIANS/MID-ATLANTIC WHILE THE 12Z GFS/ECMWF/CMC FOCUS ON ONE
SHORTWAVE. FEEL MORE COMFORTABLE LEANING ON THIS LATTER CLUSTERING
AS THEY FIT MORE REASONABLY WITH THE ENSEMBLE MEANS.


...SHORTWAVE MIGRATING FROM THE UPPER MS VALLEY TO NORTHERN NEW
ENGLAND...

FINAL PREFERENCE: A NON-12Z UKMET MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

NORTHERN STREAM ENERGY MOVING THROUGH THE UPPER MS VALLEY WILL
QUICKLY MOVE THROUGH THE GREAT LAKES AND EVENTUALLY INTO NORTHERN
NEW ENGLAND. AFTER EVALUATING ALL OF THE 12Z GUIDANCE...THE MODELS
ARE BETTER CLUSTERED THAN EARLIER WITH ONLY THE 12Z UKMET
DEPARTING FROM THE GROUPING WITH A SLIGHTLY FASTER SOLUTION.


...LONGWAVE TROF SETTING UP ACROSS THE WESTERN TO CENTRAL U.S...
...ADVANCING COLD FRONT...

FINAL PREFERENCE: BLEND OF THE 12Z ECMWF WITH THE 12Z GEFS/00Z
ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE PATTERN BECOMES MORE PROGRESSIVE DURING THIS HOLIDAY WEEKEND
AS HEIGHT FALLS TRANSLATE FROM THE NORTHWESTERN U.S. TOWARD THE
MIDDLE OF THE COUNTRY. DURING THE INITIAL 24 HOURS OF THE
PERIOD...THERE IS SYNOPTIC AGREEMENT AMONG THE MODELS WHILE
DIFFERING WITH THE SHORTWAVE DETAILS. BY DAY 2...THE 12Z NAM
BECOMES SLOWER WITH THE PROGRESSION OF THE NORTHERN EXTENT OF THE
LONGWAVE TROF. MEANWHILE...THE 12Z ECMWF HAS DEFINITELY BACKED OFF
ON THE AMOUNT OF AMPLIFICATION OCCURRING ALONG THE WESTERN EDGE OF
THE LONGWAVE TROF RELATIVE TO ITS 00Z CYCLE. DIFFERENCES BECOME
RATHER LARGE WITH THE POSITION OF THE SURFACE LOW(S) ACROSS
ONTARIO. WILL LEAN A LITTLE MORE HEAVILY ON THE ENSEMBLE MEANS
GIVEN THE GROWING SPREAD BUT INCORPORATE PORTIONS OF THE 12Z ECMWF
SOLUTION AS IT FITS THEM MOST CLOSELY.


...AMPLIFYING SHORTWAVE NEARING THE PACIFIC NORTHWEST BY TUESDAY
AFTERNOON...

FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET WITH THE 00Z ECMWF
ENSEMBLE MEAN
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

AS A LONGWAVE TROF EXTENDS FROM THE EASTERN PACIFIC INTO THE GREAT
LAKES REGION...ANOTHER AMPLIFIED SHORTWAVE WILL DIVE TOWARD THE
PACIFIC NORTHWEST BY EARLY/MID NEXT WEEK. THERE IS A TREND TOWARD
A SLIGHTLY FASTER SOLUTION WHICH INCLUDES THE 12Z ECMWF/CMC/UKMET.
THIS NOW LEAVES THE 12Z NAM/GFS BEING SLOWER OVERALL. THIS RUN OF
THE 12Z GFS LOOKS A LITTLE OFF AS IT IS DECIDEDLY SLOWER THAN ITS
OWN MEAN WITH THE 12Z GEFS MEAN NOW BEING THE FATEST SOLUTION.
WILL LEAN ON THE AFOREMENTIONED BUILDING CLUSTER AMONG THE 12Z
ECMWF/CMC/UKMET WITH MORE FOCUS ON THE 12Z ECMWF/UKMET GIVEN
PREFER THEIR HANDLING WITH THE DOWNSTREAM PORTION OF THE TROF.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

RUBIN-OSTER

$$






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