MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
247 PM EDT FRI JUL 03 2009
 
VALID JUL 03/1200 UTC THRU JUL 07/0000 UTC
 
 
...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR
INGEST...    


FINAL 12Z MODEL EVALUATION INCLUDING THE 12Z ECMWF


NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO BE SUFFICIENTLY
LARGE TO HAVE A SIGNIFICANT IMPACT ON THE FORECAST.


...TROF MOVING INTO THE NORTHWEST BY MON...

PREFERENCE:  ECMWF/UKMET BLEND... OR GFS BUT SLIGHTLY WEAKER

BY LATE IN THE FCST PERIOD THE NAM IS ABOUT 12 HRS SLOWER THAN THE
GFS WITH THE PRIMARY BUNDLE OF SHRTWV ENERGY REACHING THE PAC NW. 
THE UKMET/CANADIAN GLBL/ECMWF AND THEIR PREVIOUS RUNS AGREE WITH
THE FASTER GFS SCENARIO... WITH THE CANADIAN GLBL A LITTLE MORE
AGGRESSIVE THAN OTHER SOLNS WITH THE SEWD EXTENT OF HGT FALLS AND
THE ECMWF/UKMET A LITTLE WEAKER THAN THE GFS.  THE 00Z ECMWF
ENSEMBLE MEAN IS VERY CLOSE TO THE OPERATIONAL ECMWF... WHILE
SHRTWV DETAILS ARE FAIRLY WELL WASHED OUT IN THE 09Z SREF/12Z GEFS
MEANS LEADING TO A SLOWER OVERALL TROF THAT IS CLOSER TO THE NAM. 
EVEN WITH THIS SLOWER TIMING THE SREF/GEFS ENSEMBLES INDICATE THE
AMPLITUDE OF THE NAM TROF MAY BE EXTREME FROM LATE SUN ONWARD. 
OVER THE PAST DAY THE NAM HAS TRENDED SLIGHTLY FASTER AND THE GFS
A TAD SLOWER.  GLOBAL MODELS AS A WHOLE HAVE BEEN CONSISTENTLY
FASTER THAN THE NAM OVER THE PAST DAY... WITH ONLY SOME EARLY
UKMET RUNS HINTING AT A SLOWER NAM TIMING BEFORE ADJUSTING FASTER
IN THE PAST 12-24 HRS.  HOWEVER WITHIN THE FASTER CLUSTER THE
FASTEST SOLNS HAVE TENDED TO ADJUST A LITTLE SLOWER OVER TIME...
CONSISTENT WITH THE AMPLIFIED NATURE OF THE LARGE SCALE PATTERN. 
IN LIGHT OF THESE CONSIDERATIONS AND LIKELIHOOD THAT THE DOMINANT
OPERATIONAL CLUSTER HAS A BETTER HANDLE OF SHRTWV DETAILS... WILL
RECOMMEND THE GFS CLUSTER OVER THE NAM OR SREF/GEFS MEANS.  THE
UKMET/ECMWF RECEIVE ULTIMATE PREFERENCE DUE TO THEIR SLIGHTLY
WEAKER STRENGTH VERSUS THE GFS OR CANADIAN GLBL.  


...FLOW ALONG THE ERN HALF OF THE US-CANADIAN BORDER...

PREFERENCE:  CANADIAN GLBL... WITH SOME MODEST WEIGHTING OF LATEST
SREF/GEFS MEANS

UNUSUALLY POOR CONTINUITY/AGREEMENT AMONG LATEST GUIDANCE AND PAST
1-2 DAYS OR MORE OF RUNS LEAD TO VERY LOW CONFIDENCE IN DETAILS
BEYOND EVEN 24-36 HRS.  THE ONLY RELATIVE AGREEMENT THAT EXISTS IS
WITH LEADING ENERGY THAT CROSSES SRN NEW ENGLAND ON SAT. 
IMMEDIATELY BEHIND THIS FEATURE... THERE IS STILL A WIDE ARRAY OF
SOLNS WITH TIMING/STRENGTH OF REMAINING BUNDLES OF ENERGY.  THE
NAM AND WEAKER ECMWF ARE FASTEST.  THE CMC... WHOSE STRENGTH IS
CLOSE TO THE ECMWF... AND THE WEAKER UKMET ARE SOMEWHAT SLOWER. 
THE GFS IS THE DEEPEST/SLOWEST SOLN BUT THE CANADIAN REG GEM THRU
F48 EARLY SUN IS NOT TOO FAR FROM THE GFS IDEA.  

WITH THE LAST IN THE SERIES OF FEATURES REACHING THE GRTLKS AND
POSSIBLY NORTHEAST BY MON... THE ECMWF/UKMET/CANADIAN GLBL TO
VARYING DEGREES SUPPORT SIGNIFICANTLY SLOWER PROGRESSION THAN THE
GFS.  THE 12Z GEFS/09Z SREF MEANS DO NOT RESOLVE THIS FEATURE TOO
WELL BUT DO AGREE WITH THE BEST CLUSTERING OF GUIDANCE THAT THE
GFS MAY BE OVERDONE WITH THE AMPLITUDE OF THE TROF BY MON... AND
RECOMMEND HOLDING ONTO SOMEWHAT MORE SWWD ELONGATION OF THE TROF
THAN FCST BY THE GFS LATE IN THE FCST.

WITH THE FEATURE REACHING NEW ENGLAND SAT NIGHT-SUN... THE 12Z NAM
IS FASTER THAN PREVIOUS RUNS WHILE THE GFS HAS BEEN TRENDING
STEADILY FASTER.  WITH THE FINAL TRAILING BUNDLE OF ENERGY THE 12Z
NAM IS FARTHER S/SE THAN PREVIOUS RUNS WHILE THE GFS SHOWS A
GENERAL SWD THEN EWD TREND OVER THE PAST DAY.

PREFER AN INTERMEDIATE SOLN IN LIGHT OF NEARLY ALL THE MAJOR
GLOBAL MODELS EXHIBITING EXTREME CHANGES IN RUN TO RUN CONTINUITY
OVER THE PAST 1-2 DAYS... WITH THE PREVAILING IDEA THAT FLOW TO
THE S OF THESE FEATURES APPEARS TO BE PROGRESSIVE ENOUGH TO KEEP
ANY INDIVIDUAL SYSTEM FROM LINGERING OVER THE SAME AREA FOR TOO
LONG.  THE CANADIAN GLBL OFFERS THE BEST COMPROMISE WITH THE
FEATURE REACHING NEW ENGLAND BY EARLY SUN.  THE ECMWF MAY STILL BE
A LITTLE SLOW WITH ITS FINAL SYSTEM BUT THE FACT THAT IT FINALLY
HAS SOME SEMBLANCE OF CONTINUITY FROM A PREVIOUS RUN AND THE 12Z
GEFS MEAN IS MUCH FLATTER THAN THE GFS BY MON WOULD RECOMMEND
LEANING FURTHER FROM THE GFS.  VARIOUS CONSIDERATIONS RECOMMEND
THE CANADIAN GLBL AS THE BEST INDIVIDUAL SOLN LATE IN THE
PERIOD... WITH THE 09Z SREF/12Z GEFS MEANS ALSO PROVIDING SOME
USEFUL GUIDANCE. 


...WAVE TRACKING EWD FROM THE PLAINS AND TRAILING FRONT...
...MULTIPLE SHRTWV IMPULSES SUPPORTING THE SFC WAVE...

PREFERENCE:  UKMET/GEFS MEAN BLEND

AT SOME HRS THE NAM IS SLIGHTLY N/E OF THE GFS WITH THE WAVE
TRACKING EWD FROM THE PLAINS... WHICH CORRESPONDS TO THE NAM
BECOMING SLIGHTLY FASTER AND/OR MORE AMPLIFIED WITH THE
ILL-DEFINED SHRTWV TROF REACHING THE ERN CONUS BY SUN.  09Z SREF
ENSEMBLES OFFER DECENT SUPPORT FOR THE GFS/NAM SFC TRACK... BUT
REMAINING MODEL/ENSEMBLE GUIDANCE INCLUDING THE 12Z GEFS MEAN AS
WELL AS MOST PREVIOUS NAM AND GFS RUNS SUGGEST THE 12Z NAM/GFS
COULD BE A LITTLE TOO FAR N AND/OR E.  ALSO CONSENSUS ASIDE FROM
THE QUESTIONABLY AMPLIFIED CANADIAN GLBL FAVORS A LESS AMPLIFIED
AND/OR SLOWER MID LVL TROF THAN FCST BY THE NAM.  ALONG THE
TRAILING FRONT... THE GFS DISPLAYS SYMPTOMS OF FEEDBACK FROM THE
SRN PLAINS INTO THE LOWER MS VALLEY... SO THE CORRESPONDING GFS
SFC LOW IS VERY QUESTIONABLE.  BY LATE IN THE PERIOD THERE IS ALSO
THE QUESTION OF HOW MUCH PHASING MAY OCCUR WITH SERN CANADA/NERN
CONUS FLOW... WITH THE ECMWF AND TO A LESSER EXTENT CMC THAT ARE
SLOWER AND/OR MORE AMPLIFIED WITH NRN FEATURES LEADING TO MORE
PHASING THAN OTHER SOLNS.  THE UKMET IS SLIGHTLY FLATTER WITH NRN
STREAM FLOW AND THUS SHOWS LESS PHASING THAN THE CMC/ECMWF. 
PREFERENCE TO LEAN AWAY SOMEWHAT FROM THE ECMWF WITH NRN STREAM
FLOW LIKEWISE FAVORS LEANING AWAY FROM ITS MORE PHASED SCENARIO
LATER IN THE PERIOD... BUT GIVEN GFS FEEDBACK IN THE SOUTH AND GFS
NRN STREAM FLOW BECOMING A LESS LIKELY SCENARIO... PREFER TO GIVE
LESS WEIGHT TO THE GFS AS WELL.  WILL RECOMMEND A BLEND AMONG THE
UKMET/12Z GEFS MEAN AS THE MOST SIMPLE REPRESENTATION OF THE
PREFERRED SCENARIO THRU THE FCST.


...MODEL TREND GRAPHICS AT
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...500MB FORECASTS AT WWW.HPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML...

RAUSCH