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Model Diagnostics Discussion
 
(Latest Discussion - Issued 1857Z Sep 30, 2014)
 
Version Selection
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT TUE SEP 30 2014

VALID SEP 30/1200 UTC THRU OCT 04/0000 UTC

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

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


...TROUGH/SURFACE LOW LIFTING NORTH THROUGH THE NORTHERN PLAINS...

PREFERENCE: BLEND OF THE 12Z GFS/12Z GEFS MEAN AND THE 12Z ECMWF
CONFIDENCE: ABOVE AVERAGE

ALL OF THE MODELS SHOW A NEG-TILTED TROUGH AND ASSOCD CLOSED LOW
SFC-700 MB MOVING NWD THROUGH THE NRN PLAINS AND ACROSS THE BORDER
INTO MANITOBA BY WED MORNING AND MOVING FURTHER NORTH WED
AFTERNOON. THEE ARE SLIGHT TIMING DIFFERENCES AMONG THE FASTER
NAM/GFS AND SLOWER ECMWF/UKMET WITH THE SFC REFLECTION.  DUE TO
GOOD CLUSTERING AMONG THE 700 MB LOW SOLUTIONS...MINOR DIFFERENCES
IN THE SFC LOW REFLECTION CAN BE ADDRESSED USING A BLEND OF THESE
SOLNS.


...SURFACE LOW DEVELOPING OVER THE MID MS VALLEY AND MOVING ACROSS
THE GREAT LAKES...

PREFERENCE: BLEND OF THE 12Z GFS/12Z ECMWF/12Z CANADIAN GLOBAL
CONFIDENCE: ABOVE AVERAGE

THE MODELS INDICATE A PHASING NORTHERN STREAM AND SOUTHERN STREAM
TROUGH ACROSS THE NORTHERN AND CENTRAL PLAINS DOWNSTREAM INTO THE
MS VALLEY AND UPR MIDWEST THURS AND FRI WHICH IS EXPECTED TO SPUR
SFC-700 MB LOW DEVELOPMENT AND THE 500 MB TROUGH GRADUALLY
BECOMING SLIGHTLY NEGATIVELY TITLED.

THE 12Z NAM AND GFS ARE WITHIN THE PRIMARY CLUSTER OF SOLUTIONS
WITHIN THE MODELS AS LOW PRESSURE DEVELOPS WED AFTERNOON/EVENING. 
TIMING DIFFERENCES DEVELOP AS THU PROGRESSES WITH THE 09Z SREF
MEAN ON THE NORTHERN/FASTER EDGE OF SOLUTIONS AND 12Z UKMET
DEVELOPING THE LOW FURTHER SOUTH.  THE 12Z GEFS MEAN AND 00Z ECMWF
ENSEMBLE MEAN CLUSTER WELL WITH THE DETERMINISTIC 12Z
GFS/ECMWF/12Z CANADIAN GLOBAL SOLNS. A BLEND OF THE GFS AND ECMWF
WILL STILL BE PREFERRED. 

THE 12Z NAM BECOMES SLOWER THAN THE PRIMARY CLUSTER AS THE SFC-700
MB LOW LOW EXITS THE US ON FRI...IN SHARP CONTRAST TO THE FASTER
09Z SREF.  ALSO..THE NAM TEMPORARILY CLOSES OFF A 700 MB LOW THU
AS IT CROSSES THE EASTERN NE/IOWA CORRIDOR...AND THEN WEAKENS IT
BACK INTO AN OPEN WAVE.  THE LACK OF TEMPORAL CONTINUITY AND
DISAGREEMENT WITH OTHER SOLUTIONS RESULTS IN LOWER CONFIDENCE IN
THE 12Z NAM.

...500 MB LOW CROSSING THE NORTHERN MID ATLANTIC AND SOUTHERN NEW
YORK/NEW ENGLAND...

PREFERENCE: 12Z GFS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS TAKE THE CLOSED LOW ACROSS PA/NJ AND LONG ISLAND
NY/ADJACENT SOUTHERN NEW ENGLAND THROUGH WED NIGHT AND OFF THE
SOUTHEAST NEW ENGLAND COAST THU BEFORE GOING FURTHER OFFSHORE LATE
THU. LATITUDINAL DIFFERENCES DEVELOP WHERE SFC LOW PRESSURE BEGINS
TO DEVELOP IN THE ATLANTIC WATERS...WITH THE 00-12Z ECMWF ON THE
NORTH EDGE OF THE SUITE OF SOLUTIONS AND UKMET FURTHEST SOUTH.
ALSO...THE NAM ALLOWS THE 700 MB LOW TO LINGER FURTHER WEST NEAR
LONG ISLAND WED/WED EVENING...SO CONFIDENCE IS LOWER IN THE 12Z
NAM FCST. GIVEN A LARGE SPREAD IN SOLUTIONS DEVELOPING OVER THE
WESTERN ATLANTIC...A CONSENSUS APPROACH IS SUGGESTED UNTIL BETTER
CLUSTERING DEVELOPS...WITH THE 12Z GFS IN THE MIDDLE OF THE PACK.


www.wpc.ncep.noaa.gov/html/model2.shtml...
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

PETERSEN