Prognostic Meteorological Discussion
Issued by NWS

000
FXUS10 KWNH 231638
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1237 PM EDT THU MAY 23 2013

VALID MAY 23/1200 UTC THRU MAY 27/0000 UTC

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


12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES

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


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

PREFERENCE: NON 00Z CMC CONSENSUS
CONFIDENCE: AVERAGE

THE LATEST GUIDANCE IS IN VERY GOOD AGREEMENT WITH THE DETAILS OF
THIS DEEP UPPER LOW THROUGH FRI...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.
THE TREND HAS BEEN FOR A STRONGER LOBE OF THE CLOSED LOW TO BE
OVER BRITISH COLUMBIA AND ALBERTA ON SAT...WHILE WEAKENING THE
PIECE OVER THE E-PAC. OVERALL...RECENT MODEL GUIDANCE IS
CLUSTERING BETTER NOW AND AGREES THAT THERE SHOULD BE A CLOSED LOW
EVOLVING OVER THE PAC NW EARLY IN THE PERIOD AND THEN REORGANIZING
OVER SWRN CANADA IN AN ELONGATED FASHION ON SAT WITH LIKELY TWO
DISTINCT CENTERS AS SHORTWAVE ENERGY PIVOTS AROUND A MEAN CENTER.
THE 00Z CMC THOUGH...INSISTS ON A SEPARATE CLOSED LOW DEVELOPING
OFFSHORE OF THE PAC NW BY THE END OF THE PERIOD AS ENERGY DROPS
SEWD FROM THE GULF OF AK. THE 00Z CMC IS AN OUTLIER SOLN AND WE
WILL THEREFORE SUGGEST A NON 00Z CMC CONSENSUS ATTM GIVEN THAT THE
REMAINING MODEL GUIDANCE IS RATHER WELL CLUSTERED.


...DEEP UPPER TROUGH/CLOSED LOW MOVING FROM THE MIDWEST TO THE
NORTHEAST...

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

THERE HAS BEEN A STRENGTHENING TREND IN THE GUIDANCE REGARDING THE
CLOSED LOW NEAR LONG ISLAND LATE SATURDAY...AS MORE RECENT MODEL
GUIDANCE SEEMS TO HAVE A BETTER HANDLE ON PHASING OF A MID LEVEL
SHORTWAVE APPROACHING FROM THE LOWER GREAT LAKES. CONSIDERING 12Z
& 00Z RUNS...THE GFS HAS HELD THE BEST CONTINUITY OVER THE PAST 36
HRS AND THE 12Z NAM / 00Z ECMWF MATCH THIS SOLUTION THE BEST OF
THE DETERMINISTIC RUNS. THE 06Z GEFS MEAN SHIFTED QUICKER TO EXIT
THE CLOSED LOW FROM NEW ENGLAND AND DOES NOT HAVE SUPPORT FROM A
MAJORITY OF ENSEMBLE MEMBERS AND THE 00Z EC MEAN WHICH ARE SLOWER.
THE 00Z UKMET/CMC ARE A BIT SLOWER/SOUTHWEST OF THE NAM/GFS/ECMWF
COMBO AT TIMES...BUT OVERALL ARE USABLE AS WELL.


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

OTTO

$$