Prognostic Meteorological Discussion
Issued by NWS

000
FXUS10 KWNH 240410
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1209 AM EDT FRI MAY 24 2013

VALID MAY 24/0000 UTC THRU MAY 27/1200 UTC

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


00Z 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 GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THE LATEST GUIDANCE OVERALL IS IN VERY GOOD AGREEMENT WITH THE
DETAILS OF THIS DEEP UPPER LOW THROUGH SAT...AND THEN THERE IS A
GRADUAL INCREASE IN SPREAD THEREAFTER AS THE MODELS SHOW SOME
DISAGREEMENT WITH HOW UPSTREAM SHORTWAVE ENERGY DIGS IN FROM THE
GULF OF AK AND MOVES INLAND ACROSS THE WEST COAST. THE MODELS
AGREE ON PLACING A STRONGER CLOSED LOW CENTER OVER BRITISH
COLUMBIA AND ALBERTA ON SAT...BEFORE THEN SLOWLY WEAKENING THE
ENERGY SUN INTO MON AS ADDITIONAL UPSTREAM SHORTWAVE ENERGY
ADVANCING INLAND FROM THE E PAC AND DIGS INTO THE PAC NORTHWEST
AND GRT BASIN. THE MODELS ARE FAIRLY WELL CLUSTERED EVEN ON SUN
AND INTO MON...BUT THE 12Z UKMET APPEARS TO BE A RELATIVE OUTLIER
IN NOT HAVING A SHORTWAVE TROUGH JUST OFF THE WEST COAST EARLY
MON. THE UKMET ALSO MAY BE A LITTLE TOO SHARP WITH ITS ENERGY
TRAVERSING THE GRT BASIN BY THAT TIME. THE 12Z GEM GLOBAL FOR ITS
PART MAY BE A LITTLE TOO SLOW WITH ITS UPSTREAM ENERGY MOVING TWD
THE WEST COAST BY THE END OF THE PERIOD. THE STRONGEST MODEL
CLUSTER OVERALL APPEARS TO BE A 00Z GFS/12Z ECMWF CAMP.


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

PREFERENCE: 00Z GFS
CONFIDENCE: AVERAGE

AS MENTIONED PREVIOUSLY...THERE HAS BEEN SOME STRENGTHENING TREND
SEEN IN THE GUIDANCE REGARDING THE CLOSED LOW DEVELOPING ON FRI
OVER THE MID-ATLANTIC REGION AND THEN LIFTING NEWD UP ACROSS NEW
ENGLAND SAT AND SUN. GENERALLY THE GUIDANCE DOES APPEAR TO BE
BETTER HANDLING THE INTRUSION OF ADDITIONAL NRN STREAM SHORTWAVE
ENERGY AND ITS PHASING WITH THE UPPER TROUGH THAT IS ALREADY
ADVANCING AND DIGGING THROUGH THE OH VLY ATTM. THE 00Z GFS AGAIN
SHOWS RATHER GOOD CONTINUITY AND OVERALL HAS THE SUPPORT OF THE
00Z NAM...12Z GEM GLOBAL AND THE 12Z ECMWF. ALTHOUGH THE 12Z ECMWF
IS AGAIN PERHAPS A TAD DEEPER THAN THE MODEL CONSENSUS. BY
SAT...THE ECMWF LAGS THE GLOBAL MODEL CONSENSUS AND ALSO THE 18Z
GEFS MEAN AND 12Z ECENS MEAN WITH ITS NEWD PROGRESSION AND APPEARS
TO BE A LITTLE TOO SLOW IN LIFTING LOW PRESSURE UP ALONG THE NEW
ENGLAND COAST. THE 12Z UKMET HAS BEEN SHOWING POOR RUN TO RUN
CONTINUITY...AND IS CURRENTLY MUCH FASTER THAN ANY OTHER MODEL TO
PIVOT ITS HT FALLS NEWD THROUGH NEW ENGLAND AND UP IN SERN CANADA.
BASED ON ITS BETTER RUN TO RUN CONTINUITY...WILL FAVOR THE 00Z GFS
ATTM.


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

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

THE LATEST MODELS SUPPORT AT LEAST A WEAK MID LEVEL SHORTWAVE
TROUGH EJECTING NEWD OUT INTO THE CNTRL PLAINS SUN NIGHT AND
MOVING INTO THE MIDWEST BY EARLY MON WITH AN ATTEMPT TO MOVE
THROUGH A MEAN RIDGE AXIS. THE 00Z NAM IS LIKELY TOO STRONG WITH
IT SIGNATURE GIVEN THAT THE ENERGY IS ATTEMPTING TO TRAVERS A
LARGER SCALE RIDGE AXIS. THE 12Z UKMET APPEARS TO BE TOO
PROGRESSIVE WITH IT. THIS LEAVES THE 12Z GEM GLOBAL...12Z ECMWF
AND 00Z GFS WHICH SHOW BETTER AGREEMENT. WILL FAVOR A 00Z GFS/12Z
ECMWF BLEND ATTM WITH THIS IMPULSE.


...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

$$