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000
FXUS10 KWNH 241630
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1229 PM EDT FRI MAY 24 2013

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

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

12Z NAM/GFS EVALUATION

NO SIGNIFICANT INITIALIZATION ERRORS ARE SEEING IMPACTING THE
SHORT RANGE FORECAST.

...DEEP UPPER TROUGH/CLOSED LOW OVER THE NORTHWEST...

PREFERENCE: BLEND OF THE 00Z OR 12Z GFS AND THE 24/00Z ECMWF
CONFIDENCE: AVERAGE

THE NAM IS STRUGGLING WITH THE DETAILS OF HOW MUCH SHORTWAVE
ENERGY EJECTS FROM THE PARENT LOW OVER THE ERN NOPAC ON SUNDAY AND
BEYOND.  IT IS FLATTER/FASTER BY THE TIME THE LEAD SHORTWAVE MAKES
IT ACROSS THE ROCKIES AND THE FRONT RANGE...WHILE IT HAS MANAGED
TO CLOSE TWO MID LEVEL CENTERS OFF THE PAC NW COAST WHERE OTHER
MODELS LEFT ROOM FOR A CLOSED CENTER BUT GENERALLY REMAINED OPEN.
THE 12Z GFS CONTINUITY REMAINED VERY GOOD.

...DEEP UPPER TROUGH/CLOSED LOW MOVING FROM THE OH VALLEY THROUGH
THE MID-ATLANTIC/NORTHEAST...

PREFERENCE: BLEND OF THE 00Z OR 12Z GFS AND THE 24/00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THE TREND OVER THE PAST FEW RUNS TOWARDS STRENGTHENING THE CLOSED
LOW OVER CONTINUED IN THE 12Z NCEP MODEL CYCLE AS IT MOVES OVER
THE MID ATLANTIC REGION AND INTO THE MID ATLANTIC REGION.  THE NAM
CERTAINLY SPED UP THE FOREWARD MOTION OF THE SYSTEM COMPARED WITH
ITS RUN FROM 23/12Z.  THE GFS HAS BETTER RUN TO RUN CONTINUITY.
ONE POINT OF AGREEMENT IS THAT THE LOW IS MOVING FASTER THAN IN
PREVIOUS RUNS BY THE END OF DAY 3.  EVEN SO...THE GFS IS IN BETTER
AGREEMENT WITH THE ECMWF AND THE ENSEMBLE MEAN THAN THE NAM SO SEE
LITTLE REASON TO MAKE ANY PREFERENCE CHANGE.

...MID LEVEL SHORTWAVE TROUGH EJECTING OUT ACROSS THE CENTRAL
PLAINS/MIDWEST SUN NIGHT/MON...

PREFERENCE: BLEND OF THE 00Z OR 12Z GFS AND THE 24/00Z ECMWF
CONFIDENCE: AVERAGE

THE 12Z NAM DEAMPLIFIED THE MID LEVEL SHORTWAVE TROUGH EJECTING
NEWD OUT INTO THE CNTRL PLAINS SUN NIGHT AND MOVING INTO THE
MIDWEST BY EARLY MON.  THIS GOT THE NAM INTO BETTER AGREEMENT WITH
OTHER MODELS BUT IT REMAINED A FAST OUTLIER AND STILL ON THE
STRONG SIDE OF THE GUIDANCE.  EVEN THOUGH THE GFS ALSO HAS SOME
TIMING DIFFERENCES WITH THIS FEATURE...THE RUN TO RUN CONTINUITY
WAS PRETTY GOOD AND HAD STRONG SUPPORT FROM THE ECMWF.

...MODEL TREND GRAPHICS AT
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML...

BANN

$$