Prognostic Meteorological Discussion
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FXUS10 KWNH 091704
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1204 PM EST FRI DEC 09 2016

VALID DEC 09/1200 UTC THRU DEC 13/0000 UTC

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

12Z NAM/GFS MODEL EVALUATION ALONG WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

LOW AMPLITUDE SHORTWAVE CROSSING THE GREAT LAKES AND NEW ENGLAND
  THROUGH SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


*PROGRESSIVE SHORTWAVE CROSSING THE NRN ROCKIES SAT AND PASSING
OVER
  THE GREAT LAKES EARLY MON WITH ACCOMPANYING SURFACE LOW/FRONT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/00Z ECMWF/00Z CMC COMPROMISE
CONFIDENCE: SLIGHTLY BELOW AVERAGE

MODEST SPREAD REMAINS IN THE LATEST SPAGHETTI ENSEMBLE HEIGHTS FOR
SUN NIGHT INTO MON...BUT BETTER AGREEMENT EXISTS COMPARED TO
PREVIOUS CYCLES. GIVEN RATHER LARGE ADJUSTMENTS BETWEEN ENSEMBLE
CYCLES....CONFIDENCE IS LOWER THAN USUAL. HOWEVER...DESPITE LOWER
CONFIDENCE OVERALL...THE 00Z UKMET/CMC STAND OUT TOWARD THE EDGES
OF THE LATEST ENSEMBLE PLOTS...WITH BETTER AGREEMENT TOWARD THE
12Z GFS AND 00Z ECMWF. THE NAM IS SOMEWHAT SIMILAR TO THE
GFS/ECMWF AT 500 MB BUT IS ON THE STRONGER SIDE AT 850 MB WITH
GREATER AND MORE NORTHWARD DISPLACED LOW LEVEL WARM ADVECTION INTO
THE GREAT LAKES. AS THE UPPER SYSTEM APPROACHES THE NORTHEAST ON
MON...THE GFS/ECMWF CONTINUE TO BE REPRESENTATIVE OF A GOOD
COMPROMISE BUT DIFFER ON THE PARENT SURFACE LOW POSITION OVER SRN
ONTARIO/QUEBEC. THE ENSEMBLES CURRENTLY SUPPORT THE GFS OVER THE
ECMWF WITH THE SURFACE POSITION OVER SRN QUEBEC...WITH GENERAL
AGREEMENT REGARDING THE SURFACE LOW NEAR THE GULF OF MAINE.


CONTINUED ONSHORE FLOW INTO THE PACIFIC NORTHWEST FROM SUN-MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE

FAST MOVING PACIFIC SYSTEMS IN A QUASI-ZONAL FLOW LOCATED JUST OFF
OF THE WEST COAST MAKE FOR A DIFFICULT FORECAST. AFTER THE
DEPARTURE OF THE SHORTWAVE REFERENCED ABOVE...CONTINUED ONSHORE
FLOW INTO THE PACIFIC NORTHWEST REMAINS WITH/AHEAD OF A POSSIBLE
CLOSED LOW WEST OF WASHINGTON BY MON. A BLEND OF THE 12Z GFS AND
00Z ECMWF REPRESENT THE MIDDLE OF THE SPREAD WITH THE ECMWF FLIP
FLOPPING BETWEEN A CLOSED LOW...MORE GFS-LIKE SOLUTION...AND A
MORE ELONGATED UPPER TROUGH.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...


OTTO



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