THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


MODEL DIAGNOSTIC DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
410 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/UKMET/ECMWF


...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 12Z 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/12Z 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/NAM MOVING THE LOW FURTHER NORTH THAN THE
12Z 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 A FEW HOURS SLOWER THAN
THE 12Z GFS/12Z ECMWF/12Z CANADIAN GLOBAL.  THE NAM IS CONTRASTED
BY THE FASTER 09Z SREF MEAN.

WITH BETTER MODEL CLUSTERING...A BLEND OF THE 12Z GFS AND 12Z
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 12Z ECMWF HAS
DEAMPLIFIED THE 700 MB WAVE CROSSING THE GREAT LAKES/OHIO VALLEY
WHILE KEEPING SIMILAR TIMING OF THE SFC WAVE CROSSING PA/NY/NEW
ENGLAND...SO THE 12Z RUN IS PREFERRED. 


...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 12Z ECMWF WAS FASTER IN MOVING THE 700 MB LOW OFF THE COAST. 
GIVEN THE OTHER MODELS CLUSTER BETTER...THERE IS TOO MUCH
UNCERTAINTY TO AGREE WITH THE 12Z RUN TREND.  SINCE THERE REMAINS 
GOOD CLUSTERING WITH THE NAM/GFS/UKMET 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





Last Updated: 410 PM EDT WED OCT 01 2014