Prognostic Meteorological Discussion
Issued by NWS

000
FXUS10 KWNH 181617
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1217 PM EDT SAT MAY 18 2013

VALID MAY 18/1200 UTC THRU MAY 22/0000 UTC

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


12Z NAM/GFS EVALUATION

NO SIGNIFICANT INITIALIZATION ERRORS ARE SEEN IMPACTING THE NAM
AND GFS SHORT RANGE FORECASTS.


...DEEP CYCLONE DROPPING TOWARDS THE PACIFIC NORTHWEST...

PREFERENCE: 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

ALL OF THE MODELS SHOW GOOD AGREEMENT WITH THE IDEA OF A STRONG
UPPER TROUGH AND ASSOCD CLOSED LOW DEVELOPMENT OVER AND JUST
OFFSHORE THE PAC NORTHWEST BY TUES. THE 00Z UKMET APPEARS TO BE A
LITTLE TOO STRONG AND TOO FAR SOUTH WITH ITS VORTEX BY LATE
TUES...WITH THE 12Z GFS TENDING TO BE A LITTLE TOO FAR OFFSHORE
WITH ITS CENTER. THE 12Z NAM...00Z GEM GLOBAL AND THE 00Z ECMWF
ALL SHOW REASONABLY GOOD AGREEMENT BOTH WITH DEPTH AND PLACEMENT.
THE 00Z ECENS MEAN AND 06Z GEFS MEAN LEND BROADER SUPPORT TO THE
ECMWF LED CONSENSUS...AND SO WILL CONTINUE TO FAVOR THE 00Z ECMWF
ATTM.


...TROUGH/DEEP CYCLONE MOVING FROM THE WEST INTO THE
PLAINS/MIDWEST...

PREFERENCE: BLEND OF THE 00Z ECMWF/00Z ECENS MEAN
CONFIDENCE: AVERAGE

THE 00Z UKMET IS REALLY THE OUTLIER SOLN ATTM...WITH IT HAVING A
STRONGER CLOSED LOW DEVELOPING OVER THE N CNTRL PLAINS BY TUES VS
THE CONSENSUS. IT IS ALSO FARTHER NORTH AND STRONGER THAN ANY
MODEL WITH ITS SFC LOW. THE 12Z GFS ON THE OTHER HAND...APPEARS TO
BE WEAKENING THE SYS TOO QUICKLY BY THE END OF THE PERIOD...AS IT
HAS A WEAKER CLOSED LOW FEATURE AND IS ALSO WEAKER AND MUCH
FARTHER SOUTH WITH ITS SFC WAVE ON TUES. SPLITTING THE DIFF
INCLUDES THE 00Z GEM GLOBAL AND 00Z ECMWF WHICH CLUSTER OVERALL
QUITE WELL WITH THE DEPTH OF THE SYS. THE 12Z NAM GENERALLY AGREES
ALOFT...BUT IT BECOMES A WEAK OUTLIER AT THE SFC BY THE END OF THE
PERIOD. THE 06Z GEFS MEAN AND 00Z ECENS MEAN SUPPORT THE ECMWF/GEM
GLOBAL CAMP...BUT AT THE SFC LATE IN THE PERIOD...THE GEFS MEAN
AND ECENS MEAN SUPPORT A SFC LOW A TAD NORTHEAST OF THE
DETERMINISTIC CAMP INVOLVING THE UPPER MIDWEST. BASED ON
THIS...WILL ATTEMPT TO SPLIT THE DIFF BETWEEN THE DETERMINISTIC
AND ENSEMBLE CAMPS BY LEANING TWD A 00Z ECMWF/00Z ECENS MEAN BLEND.


...SHORTWAVE TROUGH MOVING THROUGH THE SOUTHEAST/MID-ATLANTIC...

PREFERENCE: NON-NAM COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z NAM AGAIN APPEARS TO BE A LITTLE TOO SLOW WITH THE
EVOLUTION OF THE SHORTWAVE TROUGH EXITING THE TN VALLEY AND AIMING
FOR PORTIONS OF THE INTERIOR SOUTHEAST AND MID-ATLANTIC. AT
VARIOUS TIME-PERIODS...THE NAM APPEARS A LITTLE TOO WEAK AS WELL.
THE REMAINING MODELS ARE WELL-CLUSTERED OVERALL...AND SO A NON-NAM
CONSENSUS WILL CONTINUE TO BE PREFERRED.


...MODEL TREND GRAPHICS AT
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML...
...500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML...

ORRISON

$$