MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 PM EDT MON JUN 17 2013

VALID JUN 17/1200 UTC THRU JUN 21/0000 UTC

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

12Z MODEL EVALUATION...AND FINAL PREFERENCES


...BROAD UPPER LEVEL TROUGHING OVER THE GREAT LAKES AND
NORTHEAST...
 
PREFERENCE: NON 12Z NAM COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE 

THE MOST RECENT GUIDANCE SHOWS DECENT AGREEMENT WITH BROAD UPPER
LEVEL TROUGHING AND A CLOSED CENTER TRACKING EASTWARD THROUGH
QUEBEC. HOWEVER...BY EARLY THU MORNING...THE NAM STANDS OUT AS AN
OUTLIER WITH THE SHARPNESS OF AN UPPER TROUGH OVER THE NORTHEAST.
THEREFORE...THE PREFERENCE IS FOR A LESS AMPLIFIED...NON-12Z NAM
SOLUTION.


...LOW-MID LEVEL WAVE ADVANCING EAST FROM THE CNTRL PLAINS
TODAY...REACHING THE MID-ATLANTIC WED MORNING...
...WEAK SFC LOW TRACKING ACROSS THE TENN VALLEY TOWARD THE CNTRL
MID-ATLANTIC COAST...
 
PREFERENCE: 12Z ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE 
 
A CONVECTIVELY ENHANCED LOW-MID LEVEL VORTICITY MAX IS FORECAST TO
TRACK EWD FROM THE KANSAS/OKLAHOMA BORDER...REACHING THE
MID-ATLANTIC STATES BY LATE TUE NIGHT WHILE GRADUALLY WEAKENING.
HOWEVER...ANOTHER VORTICITY MAX CURRENTLY OVER WRN NORTH
DAKOTA...IS EXPECTED TO FOLLOW QUICKLY BEHIND THE WEAKENING VORT
CENTER WED MORNING...AND ESSENTIALLY FORCE A COLD FRONT OFFSHORE
WHILE ONE OR MORE SURFACE LOWS DEVELOP ALONG THE FRONT AND MOVE
NEWD THROUGH THE WRN ATLANTIC.

THE 12Z ECMWF/UKMET HAVE CAUGHT ON WITH THE KANSAS/OKLAHOMA VORT
AND DO NOT APPEAR TO BE DRASTICALLY AFFECTED BY CONVECTIVE
FEEDBACK LATER IN THEIR FORECASTS...UNLIKE THE 12Z GFS. THE LATEST
ENSEMBLE MEANS / SPAGHETTI LOW PLOTS SUPPORT A SOLUTION FARTHER
EAST THAN THE NAM...CLOSE TO THE ECMWF/UKMET. THE 12Z CMC IS
FASTER...LIKE THE GFS...AND WILL NOT BE FAVORED UNLESS THERE ARE
CHANGES IN SUBSEQUENT MODEL RUNS TO SUPPORT THE FASTER SOLUTIONS.


...DEEP CLOSED LOW MOVING ACROSS THE PACIFIC NORTHWEST AND
NORTHERN ROCKIES...

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

STARTING EARLY THU...MODELS BEGIN TO DIFFER WITH THE SPEED OF THE
CLOSED LOW MOVING THROUGH THE NORTHWEST. THE NAM/SREF ARE
QUICKEST. THE 12Z CMC HAS SPED UP AND IS NO LONGER THE SLOWEST
DETERMINISTIC MODEL...BUT MAY BE TOO FAR SOUTH WITH THE CENTER OF
THE CLOSED LOW BY THU MORNING. THE UKMET HAS SLOWED FROM ITS 00Z
RUN AND IS NOW CLOSER TO THE MIDDLE OF THE SPREAD...JUST A BIT
AHEAD OF THE GFS/ECMWF. MOST MODELS HAVE HELD DECENT RUN-TO-RUN
CONTINUITY AND FALL WITHIN THE RATHER BROAD ENSEMBLE SPREAD. THE
ENSEMBLE MEANS SHOW GOOD AGREEMENT THOUGH...AND CLUSTER BETWEEN
THE FASTER/SLOWER SOLUTIONS...CLOSE TO THE GFS/ECMWF/UKMET...HENCE
THE PREFERENCE TOWARD THESE MIDDLE OF THE ROAD SOLUTIONS.



...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