Prognostic Meteorological Discussion
Issued by NWS

000
FXUS10 KWNH 191634
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1234 PM EDT WED JUN 19 2013

VALID JUN 19/1200 UTC THRU JUN 23/0000 UTC

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

12Z NAM/GFS EVALUATION

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

PREFERENCE: BLEND OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN AND 12Z GFS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

IN TERMS OF RUN TO RUN CONSISTENCY...BOTH THE 12Z NAM AND THE GFS
WERE FAIRLY CLOSE TO THEIR PREVIOUS RUNS IN TERMS OF PLACEMENT OF
THE CENTER OF THE LOW.  ADMITTEDLY THE GFS HAD LESS AMPLITUDE OF
THE DOWNSTREAM RIDGING BY 22/00Z WHICH ALLOWED THE MID LEVEL LOW
TO BE MORE OBLONG THAN IN THE PREVIOUS RUN.    THIS LEAVES THE NAM
AND THE OLD UKMET AS HAVING A VORT CENTER ROTATING AROUND THE
PERIPHERY OF THE LOW WHILE THE ECMWF/GFS AND RELATED MEANS SHOW
THE SAME SHORTWAVE ENERGY LAGGING TO THE SOUTH OF THE MID LEVEL
LOW CENTER.  THE RELATIVE POSITION OF THESE 12Z MODELS WAS LARGELY
UNCHANGED WITHIN THE ENVELOPE OF SOLNS.

...500 MB WAVE MOVING FROM THE CENTRAL PLAINS/UPPER MS VALLEY TO
OH VALLEY LATE DAY 1 THROUGH DAY 2...

PREFERENCE:  NON-UKMET/CANADIAN MODEL COMPROMISE
CONFIDENCE:  AVERAGE

MODELS STILL DEPICT A LOW AMPLITUDE 500 MB WAVE MOVING EAST IN
CONFLUENT FLOW FROM THE CENTRAL PLAINS TO MS VALLEY ON DAY ONE AND
WEAKENING AS IT CROSSES THE OHIO VALLEY ON DAY 2. EVENTUALLY THE
WAVE RIDES OVER THE TOP OF THE BUILDING CENTRAL RIDGE ON DAY 2 AND
CONTINUES INTO THE OH VALLEY.  STILL RELYING ON THE CLUSTERING OF
THE 12Z GFS/NAM AND OPERATIONAL 19/00Z ECMWF WITH THE ENSEMBLE
MEANS TO RECOMMEND A NON UKMET/CANADIAN COMPROMISE.

...BROAD UPPER LEVEL TROUGHING OVER THE GREAT LAKES AND
NORTHEAST...
...TRAILING SHORTWAVE ENERGY OVER THE SOUTHEAST COASTAL AREAS
FRI-FRI NIGHT...

PREFERENCE: 19/00Z ECMWF AND 12Z GFS...18/21Z SREF
CONFIDENCE: AVERAGE

THE MOST RECENT GUIDANCE SHOWS DECENT AGREEMENT WITH BROAD UPPER
LEVEL TROUGHING
ACROSS THE NORTHEAST AND LAKES DAYS 1-2 BEFORE RISING HEIGHTS AS
THE BUILDING CENTRAL US RIDGE DRIFTS EAST.  OVER THE MID ATLANTIC
AND SOUTHEAST...THE MODEL MAJORITY OF MODELS STILL SHOW AN
ELONGATED 850-500 MB CYCLONIC SHEAR ZONE WITH EMBEDDED WEAK
CIRCULATIONS SFC/ALOFT FRI-FRI NIGHT.

MINOR TIMING/INTENSITY DIFFERENCES EXIST WHICH SUGGESTS A
MULTI-MODEL/SREF ENSEMBLE MEAN CONSENSUS BE USED TO RESOLVE
DIFFERENCES.

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

BANN

$$