Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9
000
FXUS10 KWNH 011656
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1256 PM EDT WED OCT 01 2014

VALID OCT 01/1200 UTC THRU OCT 05/0000 UTC

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

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


...POWERFUL TROUGH/CLOSED LOW EXPECTED TO DEVELOP OVER THE GREAT
LAKES/MIDWEST...
...SECONDARY WAVES ROTATE UNDERNEATH THE CLOSED LOW LATE FRI
THROUGH SAT OVER THE MIDWEST TO THE MID ATLANTIC AND SOUTHERN NEW
ENGLAND...

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

THE MODELS INDICATE PHASING OF THE NORTHERN AND SOUTHERN STREAM
TROUGH ACROSS THE PLAINS AND UPR MIDWEST THURS AND FRI WITH A WAVE
SFC FRONT AND CLOSED LOW DEVELOPING AS THE LOW DEPARTS THE PLAINS
FOR THE MS VALLEY THU AND UPPER GREAT LAKES THU NIGHT/FRI MORNING.
 THERE IS CLUSTERING OF THE 12Z NAM/GFS/00Z ECMWF WITH THE 09Z
SREF MEAN ON THE EASTERN EDGE OF THE GUIDANCE SUITE WITH FASTER
TIMING OF THE LOW AND TRAILING FRONT THU NIGHT/FRI MORNING.
LARGER DIFFERENCES DEVELOP AS THE LOW CROSSES FROM THE LAKES IN
ONTARIO...WITH THE GFS FASTER TO MOVE THE LOW NORTH THAN THE
ECMWF/UKMET.

ON FRI NIGHT/SAT...A SECONDARY 500 MB WAVE DEVELOPS AND ROTATES
THROUGH THE BASE OF THE TROUGH.  THIS WAVE MAY TRIGGER
CYCLOGENESIS ALONG THE TRAILING SFC COLD FRONT IN THE MID ATLANTIC
TO SOUTHERN NEW ENGLAND.  THE 12Z NAM IS SEVERAL HOURS SLOWER THAN
THE 12Z GFS/00Z ECMWF.  THE NAM IS CONTRASTED BY THE FASTER 09Z
SREF MEAN....WITH THE 00Z CANADIAN GLOBAL EVEN SLOWER THAN THE NAM
500 MB TROUGH TIMING.

WITH BETTER MODEL CLUSTERING...A BLEND OF THE 12Z GFS AND 00Z
ECMWF WILL BE PREFERRED. THE 00Z ECMWF WAS WELL WITHIN THE
MAJORITY OF THE ENSEMBLE MEMBERS REGARDING THE TROUGH TIMING.  THE
ECMWF ENSEMBLE MEAN 700 MB WAVE IS NOT AS AMPLIFIED AS THE
OPERATIONAL FCST ACROSS THE OHIO VALLEY FRI AND CENTRAL
APPALACHIANS ON SAT.  THE 06Z GEFS MEAN EXHIBITED SIMILAR TIMING
OF THE 500 MB TROUGH COMPARED TO THE 12Z GFS.


...UPPER TROUGH/CLOSED LOW IMPACTING LONG ISLAND NY AND ADJACENT
SOUTHERN NEW ENGLAND...

PREFERENCE: MODEL CONSENSUS
CONFIDENCE: AVERAGE

THE MODELS TAKE THE SLOW MOVING CLOSED 700-500 MB LOW OVER LONG
ISLAND/COASTAL SRN NEW ENGLAND AND DRIFT IT SLOWLY EAST OFF THE
COAST OF SOUTHEAST SRN NEW ENGLAND THU AND SLOWLY OFFSHORE THROUGH
FRI. THE MODELS ARE CLUSTERING BETTER WITH OFFSHORE SFC LOW
DEVELOPMENT AND HAVE A WESTWARD EXTENSION OF THE 700 MB TROUGH TWD
AREAS JUST SOUTH OF LONG ISLAND/SRN NEW ENGLAND TONIGHT THAT
DRIFTS ACROSS THE 40N 70W BENCHMARK THURS.  ON FRI AND SAT...THE
00Z ECMWF AND 12Z NAM/GFS CLUSTER WELL WITH THE SLOW MOVING CLOSED
LOW WITH THE 12Z UKMET SLOWING DOWN TO JOIN THIS CLUSTER.

THE 00Z ECMWF AND ECMWF ENSEMBLE MEAN TRENDED SOUTH WITH THE
CLOSED LOW TRAJECTORY AND SINCE THIS INCREASED CLUSTERING WITH THE
NAM/GFS/ AND RESPECTIVE SREF/GEFS MEANS...A CONSENSUS APPROACH
SHOULD MITIGATE DIFFERENCES AMONG MODEL/ENSEMBLE SOLUTIONS.


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

PETERSEN

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.