Prognostic Meteorological Discussion
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FXUS10 KWNH 091851
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 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 MODEL EVALUATION ALONG WITH FINAL 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: BLEND OF THE 12Z GFS/00Z ECMWF
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.

DESPITE LOWER CONFIDENCE OVERALL...THE 12Z UKMET/CMC STAND OUT
TOWARD THE FLATTER EDGES OF THE LATEST ENSEMBLE PLOTS...WITH
BETTER AGREEMENT TOWARD THE 12Z GFS AND 00Z ECMWF. THE 12Z GFS IS
TOWARD THE STRONGER SIDE OF THE DETERMINISTIC MODELS AT 500 MB AND
THE NAM IS SOMEWHAT SIMILAR TO THE 12Z GFS/00Z 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.

THE ENSEMBLE CONSENSUS HAS NOT BEEN CONSISTENT FROM RUN TO
RUN...BUT CURRENT CLUSTERING SUPPORTS PLACEMENT NEAR THE 12Z GFS
JUST A BIT FLATTER AND FASTER. AS THE UPPER SYSTEM APPROACHES THE
NORTHEAST ON MON...THE GFS/ECMWF CONTINUE TO BE REPRESENTATIVE OF
A GOOD COMPROMISE BUT THEY DIFFER ON THE PARENT SURFACE LOW
POSITION OVER SRN ONTARIO/QUEBEC. THE ENSEMBLES CURRENTLY SUPPORT
THE 12Z GFS OVER THE 00Z/12Z ECMWF WITH THE SURFACE POSITION OVER
SRN QUEBEC AND REGARDING THE SURFACE LOW NEAR THE GULF OF MAINE BY
00Z/13.


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 12Z ECMWF
SWITCHING AWAY FROM THE BETTER ENSEMBLE CLUSTERING WITH THE
DEPICTION OF A CLOSED LOW ON THE WRN EDGE OF THE LATEST ENSEMBLE
SPAGHETTI HEIGHTS BY MON MORNING. THE 00Z ECMWF WAS IN A MORE
PREFERABLE PLACE COMPARED TO THE 12Z ECMWF. THE 12Z UKMET COULD BE
CONSIDERED A SECOND CHOICE AS IT IS THE NEXT CLOSEST TO THE
PREFERRED POSITION WITH THE POSSIBLE CLOSED LOW BY LATE MON.


...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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