Prognostic Meteorological Discussion
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FXUS10 KWNH 291859
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT MON AUG 29 2016

VALID AUG 29/1200 UTC THRU SEP 02/0000 UTC

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

FINAL 12Z MODEL EVALUATION...INCLUDING THE ECMWF

...UPPER TROUGH CROSSING NEW ENGLAND ON MON...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS REMAIN IN VERY GOOD AGREEMENT WITH THIS SYSTEM.

...UPPER TROUGH TRACKING ACROSS SOUTHERN CANADA THROUGH MID-WEEK...
...TROUGH AMPLIFICATION INTO THE EASTERN U.S....
...ATTENDANT COLD FRONT PROGRESSION...

PREFERENCE: BLEND OF THE GFS AND ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

WITH RESPECT TO THE UPPER LOW/TROUGH MOVING ACROSS ONTARIO INTO
SOUTHERN QUEBEC WED-THU...BOTH THE NAM/GFS HAVE TRENDED SLOWER IN
COMPARISON TO THEIR 00Z RUNS.  HOWEVER...WHILE THE MAJORITY OF THE
GUIDANCE SHOWS SHOWS AN OPEN WAVE LIFTING TOWARD THE CANADIAN
MARITIMES THU EVENING...THE NAM IS ALONE IS DIGGING A CLOSED UPPER
LOW INTO SOUTHWESTERN QUE.  THE ECMWF WHICH HAD BEEN MORE
PROGRESSIVE...HAS SLOWED AND ITS 12Z RUN IS IN GENERALLY GOOD
AGREEMENT WITH THE GFS.

...UPPER LOW/TROUGH DIGGING SOUTH OFFSHORE BRITISH COLUMBIA...
...ENERGY PIVOTING INTO THE WEST COAST BY LATE TUES/WED...
...LEAD SHORTWAVE CROSSING NORTHERN CA ON TUES...

PREFERENCE: NON-GFS COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

TIMING/STRENGTH DIFFERENCES CONTINUE WITH THE LATEST SUITE OF
MODELS REGARDING BOTH THE LARGE UPPER LOW/TROUGH SINKING SOUTH OFF
OF THE BRITISH COLUMBIA COASTLINE THROUGH MIDWEEK...AND WITH A
COMPACT VORTICITY MAX/SHORTWAVE ADVANCING INTO THE COAST OF
NORTHERN CA BY EARLY TUES.  DIFFERENCES ARE RELATIVELY MINOR UNTIL
LATE THE PERIOD WHEN THE GFS BECOMES A MORE NOTICEABLE WESTERN
OUTLIER WITH RESPECT TO THE UPPER LOW CENTERED WEST OF VANCOUVER
ISLAND AND THE UPPER TROUGH AXIS ALONG THE WESTERN U.S. COAST.

...MID-UPPER LEVEL TROUGH OVER THE SOUTHWEST...
...ENERGY WEAKENING TOWARD THE HIGH PLAINS THROUGH WED...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE IN RELATIVELY GOOD AGREEMENT ON THE EVOLUTION OF
THIS GRADUALLY WEAKENING SYSTEM. THE NAM STILL SHOWS A SLIGHTLY
MORE AMPLIFIED SYSTEM...PARTICULARLY OVER THE CENTRAL HIGH PLAINS
EARLY WED...WITH THE GLOBAL MODELS A LITTLE WEAKER. WILL PREFER A
NON-NAM CONSENSUS.

...WAVE DEVELOPING ALONG THE SOUTHEAST COAST WED-THU...

PREFERENCE: ECMWF
CONFIDENCE: BELOW AVERAGE

WHILE MOST MODELS ARE INDICATING SOME LOW LEVEL/SURFACE WAVE
DEVELOPMENT ALONG A COASTAL TROUGH POSITIONED ALONG THE GA/SC
COAST...THERE IS LARGE SPREAD WITH RESPECT TO THE TIMING AND
AMPLITUDE OF THIS FEATURE.  THE CANADIAN AND GFS ARE AMONGST THE
MOST AMPLIFIED GUIDANCE MEMBERS....WHILE THE GFS IS MORE
PROGRESSIVE AS WELL...MOVING A WELL-DEFINED WAVE QUICKLY ON THE
HEELS OF T.D. NINE.  LACKING BROAD SUPPORT FOR A SOLUTION AS
AMPLIFIED/PROGRESSIVE AS THE GFS...A SLOWER/LESS AMPLIFIED
SOLUTION...MORE SIMILAR TO THE ECMWF IS PREFERRED.
HOWEVER...GIVEN THE MODEL SPREAD...CONFIDENCE IS BELOW AVERAGE.

...WEAK MID LEVEL LOW OVER THE WESTERN GULF COAST...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THIS SYSTEM IS EXPECTED TO GRADUALLY WEAKEN AS IT DRIFTS
SOUTHWEST...WITH THE GUIDANCE SHOWING RELATIVELY MINOR DIFFERENCES.

...T.D. EIGHT MOVING TOWARD THE MID-ATLANTIC COAST...

PREFERENCE: PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY

THROUGH TUE EVENING AS THE SYSTEM MOVES NORTHWEST TOWARD
HATTERAS...THE 12Z NAM/GFS/UKMET AND 00Z ECMWF ARE IN FAIRLY GOOD
AGREEMENT WITH RESPECT TO THE TRACK THIS SYSTEM...ALTHOUGH THE
UKMET IS NOTABLY MORE AMPLIFIED.  AS THE SYSTEM RECURVES BACK TO
THE NORTHEAST...THE GFS AND NAM ARE GENERALLY EAST OF THE
UKMET/ECMWF.  PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY FOR
MORE INFORMATION.

...T.D. NINE MOVING INTO THE GULF OF MEXICO...

PREFERENCE: PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY

OVERALL THE TREND IN THE 12Z NAM/GFS/UKMET HAS BEEN TO LIFT THIS
SYSTEM MORE SLOWLY TO THE NORTH ALONG A MORE WESTERLY TRACK ACROSS
THE EASTERN GULF.  WHILE THE ECMWF HAS SHOWN A SIMILAR TREND...IT
IS STILL ALONG THE EASTERN EDGE OF THE LATEST GUIDANCE.  PLEASE
CONSULT THE LATEST NHC FORECAST ADVISORY FOR MORE INFORMATION ON
T.D. NINE.

PEREIRA

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

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

$$





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