Prognostic Meteorological Discussion
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000
FXUS10 KWNH 310657
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT FRI OCT 31 2014

VALID OCT 31/0000 UTC THRU NOV 03/1200 UTC

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


00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE
ECMWF


...TROUGH AMPLIFYING ACROSS EASTERN NORTH AMERICA...

PREFERENCE: BLEND OF 00Z ECMWF AND 00Z UKMET
CONFIDENCE: AVERAGE

CYCLOGENESIS IS EXPECTED TO INITIATE FRIDAY AFTERNOON OFFSHORE THE
SOUTHERN MID-ATLANTIC COAST...WITH A LOW CENTER THAT IS THEN
EXPECTED TO LIFT NORTH-NORTHEAST TO JUST EAST OF THE BENCHMARK
LATE SATURDAY AND THEN TO NEAR THE GULF OF MAINE ON SUNDAY.
MEANWHILE...A SECOND LOW CENTER IS EXPECTED TO DEVELOP IN
ASSOCIATION WITH A VERY STRONG PV ANOMALY/VORT CENTER THAT DIVES
SOUTHEAST FROM THE UPPER GREAT LAKES REGION ON FRIDAY DOWN TO THE
SOUTHERN APPALACHIANS AND SOUTHEAST COASTAL PLAIN ON SATURDAY.
THIS INTENSE SHORTWAVE SHOWS UP VERY WELL IN THE LATEST GOES-RGB
AIRMASS IMAGERY...INDICATIVE OF HOW ROBUST THIS ENERGY IS ON THE
DYNAMICAL FRONT. THIS SECOND LOW CENTER WILL LIFT NORTHEAST
OFFSHORE THE MID-ATLANTIC COAST SATURDAY NIGHT AND OFFSHORE NEW
ENGLAND ON SUNDAY WHILE GRADUALLY BECOMING THE DOMINANT LOW CENTER
IMPACTING THE NORTHEAST.

THERE IS FAIRLY GOOD MODEL CLUSTERING ON THE LARGE SCALE...BUT A
NUMBER OF SMALLER SCALE DIFFERENCES APPEAR ACROSS THE MID-ATLANTIC
AND NORTHEAST SATURDAY AND SUNDAY AND ESPECIALLY RELATING TO
TIMING AND TRACK OF LOW PRESSURE OFF THE EAST COAST. RUN TO RUN
VARIABILITY IS RATHER PROBLEMATIC WITH THE GFS AND THE GEFS. THE
GFS IS THE FARTHEST LEFT AND THE STRONGEST WITH SURFACE LOW
PRESSURE IMPACTING THE NORTHEAST. THE GEM IS FARTHEST OFFSHORE.
THE ECMWF...NAM AND UKMET SPLIT THE DIFFERENCE...BUT THE UKMET AND
ECMWF ARE MORE STRONGLY CLUSTERED AND ARE A TAD EAST OF THE GFS
SOLUTION. THE LATEST ECENS MEAN IS RIGHT OF THE DETERMINISTIC
ECMWF. THE LATEST GEFS MEAN IS CLOSE TO THAT OF THE DETERMINISTIC
GFS. THE STRONGER MODEL CLUSTERING AT THIS POINT WOULD TEND TO
FAVOR THE 00Z UKMET AND 00Z ECMWF FOR MASS FIELDS...AND SO WILL
PREFER THIS CLUSTER.


...UPPER TROUGH AND DEVELOPING SPLIT FLOW IMPACTING THE WEST...

PREFERENCE: 00Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS CLUSTER FAIRLY WELL WITH THE UPPER TROUGH THAT
INITIALLY COMES INTO THE WEST BY EARLY SATURDAY.
THEREAFTER...SPLIT FLOW SETS UP WITH A NORTHERN STREAM PORTION OF
THE TROUGH PROGRESSING THROUGH THE NORTHERN ROCKIES AND THE
NORTHERN PLAINS THROUGH SUNDAY. A SOUTHERN STREAM PORTION OF THE
TROUGH DIGS BODILY INTO THE SOUTHWEST U.S. WITH A CLOSED LOW
FEATURE. THE 00Z GFS...00Z NAM AND TO A LESSER EXTENT THE 00Z
UKMET ARE ALL LIKELY TOO PROGRESSIVE WITH THE NORTHERN STREAM
ENERGY AS BOTH THE LATEST GEFS MEAN AND ECENS MEAN FAVOR A
SOLUTION THAT IS SLOWER AND CLOSER TO A CONSENSUS OF THE 00Z ECMWF
AND 00Z GEM. THE 00Z GFS IS THE FASTEST SOLUTION WITH THE SOUTHERN
STREAM ENERGY. THE 00Z NAM...00Z UKMET...00Z GEM AND 00Z ECMWF ARE
ALL CLUSTERED RATHER WELL ON A SOMEWHAT SLOWER SOLUTION. THE
LATEST GEFS MEAN AND ECENS MEAN FAVOR A SOLUTION CLOSE TO THAT OF
THE ECMWF. BASED ON THE OVERALL MODEL SPREAD AND ENSEMBLE
SUPPORT...WILL FAVOR THE ECMWF FOR BOTH STREAMS AT THIS TIME.


...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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