Prognostic Meteorological Discussion
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FXUS10 KWNH 281653
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1252 PM EDT THU AUG 28 2014

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

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

...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY
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 TROF CROSSING NORTHERN NEW ENGLAND THIS AFTERNOON...

PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS
FORECAST CONFIDENCE: HIGH

AN UPPER TROF SEEN ON WATER VAPOR IMAGERY IS FORECAST TO CONTINUE
SLIDING EASTWARD WITH THE SYSTEM EXITING NORTHERN NEW ENGLAND
LATER TONIGHT. MODELS ARE IN CLOSE ENOUGH AGREEMENT TO SUPPORT A
GENERAL MODEL CONSENSUS.


...SLOW-MOVING UPPER LOW CROSSING THE CENTRAL PLAINS...
...EVENTUALLY MERGING WITH NORTHERN STREAM ENERGY...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
FORECAST CONFIDENCE: AVERAGE

NUMEROUS SHOWERS AND THUNDERSTORMS CONTINUE TO FIRE AHEAD OF A
SLOW-MOVING UPPER CYCLONE WHICH IS CURRENTLY MOVING ACROSS THE
CENTRAL HIGH PLAINS. THROUGH FRIDAY EVENING...THE MODELS ARE IN
GOOD AGREEMENT WITH THE TIMING OF THE INITIAL UPPER LOW. MODEL
DIFFERENCES BEGIN TO EMERGE WITH THE TIMING OF THE NORTHERN STREAM
SYSTEM AND HOW QUICKLY THE TWO MERGE AS ONE. BY EARLY
SATURDAY...THE 12Z NAM/GFS ARE ON THE QUICKER SIDE PHASING THE TWO
WHILE THE OTHER DETERMINISTIC MODELS SHOW A TRAILING BATCH OF
ENERGY CROSSING THE DAKOTAS. FOR NOW WILL SPLIT THE DIFFERENCE
BETWEEN THE PAIR OF CAMPS AND FAVOR A BLEND OF THE 12Z GFS/00Z
ECMWF.


...SYSTEM LIFTING FROM THE GULF OF MEXICO INTO THE LOWER MS VALLEY
BY LATE FRIDAY...

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

EARLY IN THE PERIOD A MID-LEVEL IMPULSE WILL SETTLE ACROSS THE
WESTERN GULF COAST WHILE EVENTUALLY DRIFTING SOUTHWARD ALONG THE
COASTLINE. ALL OF THE MODELS SHOW THIS FEATURE QUITE WELL ALTHOUGH
THE 12Z NAM BECOMES VERY AGGRESSIVE IN BRINGING SEVERAL ADDITIONAL
SHORTWAVES INTO SOUTH TX. THIS ULTIMATELY LEADS TO VERY HEAVY
RAINFALL ON DAY 2. THE REMAINING MODELS SUGGEST THE FOCUS SHOULD
BE FARTHER UP THE COAST TOWARD THE TX/LA BORDER. MORE
SPECIFICALLY...THE 12Z GFS AND 00Z ECMWF/UKMET ALL SHOW THE CORE
OF THE ENERGY CROSSING SOUTHWESTERN LA BY 30/1200Z. ON THE OTHER
SIDE IS THE 00Z CMC WHICH IS QUICKER AND SHEARS THE SYSTEM OVER
THE OZARKS. WILL FAVOR THE AGREEMENT AMONG THE 12Z GFS AND 00Z
ECMWF/UKMET HERE.


...BROAD LONGWAVE TROF ANCHORING THE WESTERN TO CENTRAL U.S. THIS
WEEKEND...

PRELIMINARY PREFERENCE: BLEND OF THE 00Z ECMWF WITH THE 06Z
GEFS/00Z ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: AVERAGE

DURING THE WEEKEND...THE LONGWAVE PATTERN BEGINS TO FEATURE A
BROAD TROF EXTENDING FROM THE WEST COAST INTO THE CENTER OF THE
COUNTRY WHILE POSITIVE HEIGHT ANOMALIES ANCHOR THE GREAT LAKES
DOWN INTO THE OH/TN VALLEYS. WHILE THE DETERMINISTIC MODELS VARY
IN THE PLACEMENT OF THIS TROF...THE 576-DM SPAGHETTI PLOTS SHOW
FAIRLY WELL CLUSTERED ENSEMBLE MEMBERS. WILL LEAN MORE HEAVILY ON
THE STRONGLY CLUSTERED 06Z GEFS/00Z ECMWF ENSEMBLE MEANS WHICH HAS
SUPPORT FROM THE 00Z ECMWF.



...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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