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497
FXUS10 KWNH 241842
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EDT FRI OCT 24 2014

VALID OCT 24/1200 UTC THRU OCT 28/0000 UTC

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


12Z MODEL EVALUATION WITH PREFERENCES

NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO DEGRADE THEIR SHORT
RANGE FORECASTS.


...DEEP CYCLONE MOVING INTO THE PACIFIC NORTHWEST SATURDAY...
...MID-UPPER TROUGH MOVING ACROSS THE INTERMOUNTAIN WEST SUNDAY TO
CENTRAL/NORTHERN PLAINS MONDAY

PREFERENCE: 06Z GFS/12Z ECMWF COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z ECMWF/12Z UKMET/06Z GFS/12Z NAM/12Z GEFS MEAN CLUSTER WELL
WITH THE TRACK OF THE SFC LOW MOVING FROM THE PACIFIC JUST OFF THE
OREGON COAST AND INTO WA STATE...WITH MINOR TIMING DIFFERENCES.
THE LOW OCCLUDES IN SOUTHWEST CANADA AND A TRIPLE POINT LOW FORMS
ON THE LEE SIDE OF THE ROCKIES IN THE NORTHERN PLAINS SUNDAY.  THE
12Z GFS MADE A SIGNIFICANT CHANGE TO SLOW DOWN THE LOW AS IT
REACHES THE COAST AND FALLS BEHIND THE OTHER MODELS WITH A FURTHER
WEST POSITION 06Z-12Z SUN.  THE 12Z GEFS MEAN AND OPERATIONAL 06Z
GFS CLUSTER BETTER WITH THE OTHER MODELS...SO CONFIDENCE IS LOW IN
THE 12Z GFS ADJUSTMENT.

THE 12Z ECMWF HAS SLOWED THE LOW AND FRONTAL PROGRESSION A FEW
HOURS IN THE NORTHERN PLAINS...WITH CLUSTERING AMONG THE ECMWF/09Z
SREF MEAN/12Z NAM/12Z UKMET GOOD WITH THE LOW SUN NIGHT AND MON AS
IT APPROACHES THE CANADIAN BORDER.

THE 00Z-12Z CANADIAN WAS A SLIGHTLY DEEP OUTLIER AT 500 MB ACROSS
MT EARLY MONDAY AND THE NORTHERN PLAINS MONDAY AFTERNOON, AND ITS
SURFACE SOLUTION IS FURTHER SOUTH THAN THE OTHER GUIDANCE ACROSS
THE NORTHERN PLAINS.  LESS WEIGHTING IS GIVEN THE 00Z-12Z CANADIAN
GIVEN THE THE MAJORITY CLUSTER SFC LOW FURTHER NORTH ALONG THE
US/CANADIAN BORDER.


...CYCLONE DEVELOPING OVER NORTHERN NEW ENGLAND INTO ATLANTIC
CANADA...

PREFERENCE: MODEL CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 12Z GFS TRENDED TO A MORE SOUTHEAST DEVELOPMENT LOCATION OVER
QUEBEC WITH BETTER OVERLAP NOW WITH ITS SOLUTIONS AND THE 09Z SREF
MEAN/12Z ECMWF/12Z UKMET.  AS A RESULT OF AN IMPROVED CLUSTERING
OF SOLUTIONS...A CONSENSUS OF THESE SOLUTIONS IS RECOMMENDED.  THE
12Z NAM IS JUST A TAD SOUTH OF THE PRIMARY CLUSTER AS THE LOW
CROSSES NORTHERN MAINE.

...CYCLONE MOVING EAST TOWARDS VANCOUVER ISLAND MON-MONDAY
EVENING...

PREFERENCE: 06Z GFS/09Z SREF MEAN/12Z NAM/12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE IN AGREEMENT ON THE CLOSED LOW DEVELOPING IN THE
NORTHEAST PACIFIC AND MOVING EAST NORTHEAST IN THE DIRECTION OF
VANCOUVER ISLAND LATE MON-MON EVENING.
THERE ARE TYPICAL TIMING/TRACK DIFFERENCES WITH THE 12Z ECMWF
TRENDING NORTHWEST TO JOIN THE DOMINANT CLUSTER OF THE 00Z ECMWF
ENSEMBLE MEAN/06Z-12Z GFS/12Z GEFS MEAN/09Z SREF MEAN/12Z NAM ON
THE CYCLONE TRACK AND TIMING.  THE CANADIAN MODELS IS ON THE WEST
EDGE OF THE MODEL CLUSTER BUT WITHIN THE NORMAL SPREAD OF
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

$$






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