Prognostic Meteorological Discussion
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000
FXUS10 KWNH 301648
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1248 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


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

PREFERENCE: BLEND OF THE 12Z GFS/06Z GEFS MEAN AND THE 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

ALL OF THE MODELS SHOW A NEG-TILTING TROUGH AND ASSOCD CLOSED LOW
SFC-700 MB MOVING NWD ACROSS UP 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 AND 00Z ECMWF
CONFIDENCE: SLIGHTLY 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 ECMWF AND
09Z SREF MEAN ON THE NORTHERN/FASTER EDGE OF SOLUTIONS AND 00Z
UKMET DEVELOPING THE LOW FURTHER SOUTH.  THE 06Z GEFS MEAN AND 00Z
ECMWF ENSEMBLE MEAN CLUSTER WELL WITH THE DETERMINISTIC 12Z
GFS/00Z ECMWF 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 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 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.


...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

$$




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