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Model Diagnostics Discussion
 
(Latest Discussion - Issued 1853Z Nov 25, 2014)
 
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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
152 PM EST TUE NOV 25 2014

VALID NOV 25/1200 UTC THRU NOV 29/0000 UTC

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

12Z MODEL EVALUATION AND PREFERENCES

...SHORTWAVE TROUGH/LOW PRESSURE TRACKING FROM THE N. PLAINS TO
THE APPALACHIANS TODAY THROUGH WED...

PREFERENCE: GFS/UKMET/ECMWF
CONFIDENCE: AVERAGE

OVERALL THE NAM/GFS HAVE SHOWN GOOD RUN-TO-RUN CONTINUITY.  IN
COMPARISON TO THE NON-NCEP RUNS...THE NAM IS A LITTLE MORE
AMPLIFIED IN THE BASE OF THE UPPER TROUGH AS IT MOVES FROM THE MID
MS VALLEY INTO THE TN VALLEY ON WED.  THE 12Z ECMWF HAS SPED UP
FROM ITS PREVIOUS RUN AND IS NOW IN BETTER AGREEMENT WITH THE GFS
AS THE TROUGH MOVES ACROSS THE LOWER OH/TN VALLEYS WED NIGHT. 
OVERALL...THE 12Z GFS/UKMET/ECMWF FALL CLOSEST TO THE MIDST OF THE
CURRENT MODEL SPREAD.

...LOW PRESSURE TRACKING UP THE EAST COAST TONIGHT THROUGH WED
NIGHT...

PREFERENCE: GFS/NAM/ECMWF/UKMET COMPROMISE THROUGH 12Z
THU...FOLLOWED BY A NAM/ECMWF COMPROMISE THEREAFTER 
CONFIDENCE: AVERAGE

WITH REGARDS TO THE SURFACE LOW TRACK...BOTH THE NAM/GFS HAVE
REMAINED GENERALLY CONSISTENT WITH THEIR 00Z RUNS.  ONE SUBTLE
DIFFERENCE OF NOTE IS THAT THE 12Z NAM IS A MILLIBAR OR TWO DEEPER
AND MAYBE A LITTLE SLOWER THAN ITS 00Z RUN AS THE LOW TRACKS ALONG
THE MID ATLANTIC COAST TONIGHT.  IN CONTRAST...THE 12Z GFS HAS
SHIFTED A LITTLE WEAKER AND FASTER THAN ITS 00Z RUN DURING THAT
SAME TIME FRAME. 

IN COMPARISON TO THE NON-NCEP MODELS...THE GFS IS A LITTLE
FASTER/WEAKER THAN THE OTHER MODELS...BUT OVERALL THE 12Z
NAM/GFS/ECMWF/UKMET ARE ALL IN FAIRLY GOOD AGREEMENT WITH THE
SURFACE LOW TRACK THROUGH TOMORROW.  NOT UNTIL THU MORNING AS THE
LOW APPROACHES NOVA SCOTIA DO SOME SIGNIFICANT DIFFERENCES BETWEEN
THOSE FOUR MODELS START TO EMERGE...WITH THE UKMET/ECMWF BECOMING
NOTABLY SLOWER/DEEPER THAN THE NCEP MODELS.  BY 12Z THU...THE MEAN
OF THE ENSEMBLE SPREAD SUGGESTS A POSITION THAT FALLS BETWEEN THE
NAM AND THE ECMWF.  THE ONLY TRUE OUTLIER PRIOR TO THAT IS THE
CANADIAN GLOBAL...WHICH HAS TRENDED TOWARD THE CONSENSUS BUT IS
FASTER AND WELL EAST OF THE OTHER MODELS BY WED AFTERNOON.

IT SHOULD BE NOTED THAT WHILE THE MODELS ARE IN GOOD AGREEMENT
WITH RESPECT TO THE LARGER-SCALE FEATURES INCLUDING THE SURFACE
LOW AND UPPER SHORTWAVE TROUGH...DIFFERENCES IN THE DETAILS
REMAIN.  REFER TO WPC'S QUANTITATIVE PRECIPITATION FORECAST AND
HEAVY SNOW DISCUSSIONS FOR FURTHER DETAILS AND PREFERENCES
CONCERNING THE DIFFERENCES WITH RESPECT TO MODEL QPFS AND THERMAL
PROFILES.

...SHORTWAVE TROUGH DIGGING THROUGH BRITISH COLUMBIA AND OFFSHORE
LOW INFLUENCING THE PAC NORTHWEST THU/FRI...

PREFERENCE: GFS/ECMWF
CONFIDENCE: AVERAGE

12Z NAM/GFS HAVE NOT SHOWN ANY SIGNIFICANT CHANGES FROM THEIR 00Z
RUNS AND THEREFORE THE NAM REMAINS THE RELATIVE OUTLIER HERE...AS
IT SHOWS MORE PHASING WITH A NORTHERN TROUGH DIGGING SOUTH THROUGH
BRITISH COLUMBIA AND AN OFFSHORE OFFSHORE LOW.  THE NAM THEN
BRINGS THESE PHASED FEATURES ONSHORE LOWERING HEIGHTS MORE
AGGRESSIVELY ACROSS OREGON AND FAR NORTHERN CA ON FRI.  WHILE THE
12Z UKMET HAS TRENDED TOWARD THE NAM...NONE OF THE ENSEMBLE
MEANS...INCLUDING THE 15Z SREF...SUPPORT A SIMILAR SOLUTION.  WILL
CONTINUE TO RECOMMEND THE GFS/ECMWF...WHICH HAVE MORE ENSEMBLE
SUPPORT.

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

PEREIRA