Prognostic Meteorological Discussion
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000
FXUS10 KWNH 010440
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1240 AM EDT SAT AUG 01 2015

VALID AUG 01/0000 UTC THRU AUG 04/1200 UTC

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

00Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES

SHORTWAVE TROUGH OVER NORTHWEST MEXICO...

PREFERENCE:  BEFORE 12Z SUN...NAM OR GFS OR ECMWF
              AFTER 12Z SUN...ECMWF

CONFIDENCE:  AVERAGE

MODEL AGREEMENT IS GOOD THROUGH 12Z SUN...BY WHICH TIME THE
NAM...DUE TO EARLIER INFLUENCES FROM A CLOSED LOW NEARING THE
PACIFIC NORTHWEST...PIVOTS THE TROUGH ACROSS THE CENTRAL ROCKIES
AND INTO THE PLAINS...GENERALLY ALONG EASTERN EDGES OF THE
GUIDANCE.  GIVEN LITTLE OR NO SUPPORT FOR THIS
SOLUTION...RECOMMEND DISCOUNTING THE NAM AFTER 12Z SUN.  AMONG THE
REMAINING SOLUTIONS...THE GFS MOVES TOWARD THE DEEP EDGE OF THE
GUIDANCE CROSSING THE ROCKIES...MOST EVIDENT AT 700 MB....WHILE
THE ECMWF IS CLOSEST TO THE CONSENSUS AND HAS STRONGER RUN-TO-RUN
CONTINUITY.  THUS...RECOMMEND THE ECMWF AFTER 12Z SUN.

CLOSED LOW NEARING THE PACIFIC NORTHWEST MON-TUE...

PREFERENCE:  GFS
CONFIDENCE:  AVERAGE

THE NAM IS ALMOST A FAST OUTLIER AND THUS IS DISCOUNTED.
OTHERWISE...THE GFS AND ECMWF ARE QUITE CLOSE TO EACH OTHER...WITH
THE GFS TRENDING SLOWER.  BETWEEN THE GFS AND ECMWF THOUGH...THE
GFS IS CLOSER TO THE CONSENSUS AND HAS STRONGER SUPPORT FOR THE
LEADING EDGE OF THE TROUGH MOVING INLAND AHEAD OF THE LOW...FOR
WHICH THE ECMWF MOVES TOWARD THE FAST AND STRONG EDGES OF THE
GUIDANCE OVER MONTANA.

SHORTWAVE TROUGH CROSSING THE GREAT LAKES/OH VALLEY MON...

PREFERENCE: ECMWF
CONFIDENCE: AVERAGE

THE NAM AND GFS SHOW ARE OCCASIONALLY NEAR STRONG EDGES OF THE
GUIDANCE WITH ACCOMPANYING SURFACE LOWS APPROACHING THE
REGION...WHILE THE ECMWF HAS THE BEST RUN-TO-RUN CONTINUITY AND
SUPPORT FROM THE ENSEMBLE MEANS.  THUS...RECOMMEND THE ECMWF.

FRONTAL BOUNDARY ACROSS THE SOUTHEAST...

PREFERENCE:  HALFWAY BETWEEN THE GFS/ECMWF
CONFIDENCE:  BELOW AVERAGE

THE NAM...AT TIMES ALONG WITH THE UKMET/CANADIAN...ARE STRONGER
AND MORE INLAND WITH LOW PRESSURE FORMING ALONG THE RESIDUAL FRONT
HELPING TO PIVOT IT NORTHWARD....WHILE THE GFS AND ECMWF ARE
WEAKER...FARTHER SOUTH...AND BETTER SUPPORT BY THE GFS/ECMWF
ENSEMBLE MEMBERS.  THUS...RECOMMEND A SOLUTION ABOUT MIDWAY
BETWEEN THE GFS/ECMWF.

...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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