Prognostic Meteorological Discussion
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000
FXUS10 KWNH 271825
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 PM EDT WED MAY 27 2015

VALID MAY 27/1200 UTC THRU MAY 31/0000 UTC

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

12Z NAM/GFS EVALUATION INCLUDING THE UKMET/CANADIAN/ECMWF AND
PREFERENCES

SHORTWAVE TROUGH OVER THE UPPER MIDWEST...

MODELS SHOW GOOD LARGE-SCALE AGREEMENT.

SHORTWAVE TROUGH OVER THE LOWER MS VALLEY...

PREFERENCE: BEFORE 00Z THU...HRRR/RAP
             AFTER 00Z THU...RAP/NAM/GFS/ECMWF
CONFIDENCE: BELOW AVERAGE

THE NAM AND GFS SUFFER FROM SIGNIFICANT SPIN UP ERROR WITH THE MCS
OVER THE LOWER MS VALLEY.  IN ADDITION TO DEPICTING LESS RAINFALL
EARLY IN THE PERIOD IN ASSOCIATION WITH THE MCS...THE
GFS 2M INITIALIZATION DEWPOINTS ACROSS MOST OF NORTHERN TEXAS ARE
5 TO 10 DEGREE F TOO HIGH...WHICH IS LIKELY CONTRIBUTING TO TOO
HIGH CAPE/LOW CIN FIELDS RESPECTIVELY EARLY IN THE FORECAST CYCLE.
 THE NEW ECMWF APPEARS TO INITIALIZE WELL INCLUDING THE SUBSIDENCE
OVER NORTHEAST TEXAS. MEANWHILE...THE HRRR/RAP ARE CLOSEST TO THE
OBS AND MAY BE THE MOST USEFUL EARLY IN PERIOD.  AFTER THE END
TIMES OF THE HRRR/RAP...RECOMMEND MERGING THEIR SOLUTIONS WITH THE
NAM/GFS/ECMWF WHICH ARE THE BEST AVAILABLE BUT STILL TOO WEAK IN
MOST CASES.

SHORTWAVE TROUGH NEAR THE CO/KS BORDER...

PREFERENCE: EQUAL BLEND GFS/ECMWF
CONFIDENCE: ABOVE AVERAGE

THE GFS ALIGNS BEST WITH SATELLITE IMAGERY AT INITIALIZATION WITH
THE NAM/ECMWF A CLOSE SECOND AND THUS APPEAR TO DEPICT PLAUSIBLE
MID-LEVEL EVOLUTIONS THROUGH THE PERIOD.  HOWEVER...GIVEN STRONGER
AGREEMENT FOR THE GFS/ECMWF CAMP...THE RECOMMENDATION IS FOR A
BLEND OF THE GFS/ECMWF.

CLOSED LOW OVER THE PACIFIC NORTHWEST...
COLD FRONT CROSSING THE PLAINS/MS VALLEY FRI...

PREFERENCE: EQUAL BLEND GFS/ECMWF
CONFIDENCE: AVERAGE

THE NAM MOVES STEADILY TOWARD THE FAST AND DEEP SIDES OF THE
GUIDANCE ALOFT THUS INFLUENCING ITS FRONTAL TIMING...WHILE THE
GFS/ECMWF SHOW GOOD AGREEMENT WITH EACH OTHER WHILE DISPLAYING
SOME TYPICAL STRENGTH/TIMING DIFFERENCES.  GIVEN ADDITIONAL
SUPPORT FROM THE ENSEMBLE MEANS...
RECOMMEND DISCOUNTING THE NAM IN FAVOR OF A GFS/ECMWF BLEND.

CLOSED LOW REACHING SOUTHWEST CANADA SATURDAY...

PREFERENCE: NAM OR GFS OR ECMWF
CONFIDENCE: AVERAGE

OTHER THAN THE UKMET...WHICH BECOMES A FAST OUTLIER...MODELS SHOW
GOOD LARGE-SCALE AGREEMENT.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

JAMES

$$





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