Prognostic Meteorological Discussion
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550
FXUS10 KWNH 300430
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1229 AM EDT TUE AUG 30 2016

VALID AUG 30/0000 UTC THRU SEP 02/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


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

PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 00Z NAM IS A TAD SLOWER AND DEEPER THAN THE MULTI-MODEL
CONSENSUS WITH THE LARGE SCALE TROUGH AMPLIFYING SOUTHEAST FROM
SOUTHERN CANADA AND INTO THE EASTERN U.S. OVER THE NEXT FEW DAYS.
THE GLOBAL MODELS ARE REASONABLY WELL CLUSTERED THEIR MASS FIELD
EVOLUTION...AND FOR NOW WILL MAINTAIN CONTINUITY AND CONTINUE TO
LEAD TOWARD A GFS/ECMWF BLEND.


...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: BLEND OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF
CONFIDENCE: AVERAGE

THE GUIDANCE IS IN GOOD AGREEMENT ON THE DEPTH AND TIMING OF A
LEAD SHORTWAVE IMPULSE THAT ARRIVES ACROSS NORTHERN CA ON TUES OUT
AHEAD OF A LARGER SCALE DEEP TROUGH AND CLOSED LOW THAT ADVANCES
SOUTH FROM OFFSHORE BRITISH COLUMBIA AND THEN BEGINS DIGGING INTO
THE NORTHWEST U.S. THURS AND FRI. THE 00Z NAM AND 12Z CMC BOTH
GRADUALLY BECOME THE SLOWEST SOLUTIONS TO ADVANCE THE HEIGHT FALLS
INTO PACIFIC NORTHWEST. THE 12Z ECMWF IS THE MOST
PROGRESSIVE...WITH THE 00Z GFS AND 12Z UKMET CLUSTERED IN BETWEEN
THE SLOWER AND FASTER CAMPS. HOWEVER...THE 00Z GFS IS ACTUALLY THE
STRONGEST WITH ITS HEIGHT FALLS. WILL SUGGEST A MULTI-MODEL
CONSENSUS HERE...WITH A BLEND OF THE 00Z GFS/12Z UKMET AND 12Z
ECMWF.


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

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE IN REASONABLY GOOD AGREEMENT ON THE EVOLUTION OF
THIS GRADUALLY WEAKENING SYSTEM.


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

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

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


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

PREFERENCE: 00Z GFS
CONFIDENCE: BELOW AVERAGE

WHILE MOST MODELS ARE INDICATING SOME LOW LEVEL/SURFACE WAVE
DEVELOPMENT OVER NORTHERN FL AND THEN NORTHEAST ALONG A COASTAL
TROUGH POSITIONED ALONG THE GA/SC COAST...THERE IS LARGE SPREAD
WITH RESPECT TO THE TIMING AND AMPLITUDE OF THIS FEATURE. ALL OF
THE GUIDANCE SHOWS THIS LOW CENTER LIFTING NORTHEAST ON THE HEELS
OF T.D. NINE WHICH WILL EXITING AWAY FROM THE EAST COAST. THE 12Z
CMC AND TO A LESSER EXTENT THE 00Z NAM ARE THE STRONGEST
SOLUTIONS. THE 00Z GFS AND 12Z UKMET ARE MUCH WEAKER...WITH THE
GFS THE MOST PROGRESSIVE WITH THIS SYSTEM. THE 12Z ECMWF THOUGH IS
OVERALL THE WEAKEST AND MOST ILL-DEFINED WITH THIS SEPARATE WAVE.
THE DYNAMICAL SUPPORT FOR THIS LOW WILL BE A MID/UPPER LEVEL LOW
WHICH IS CURRENTLY OFF THE SOUTHEAST COAST AND EXPECTED DRIFT
INLAND OVER THE COASTAL PLAIN BEFORE THEN LIFTING NORTHEAST AHEAD
OF THE STRONGER UPPER TROUGH DIGGING INTO THE EASTERN U.S. THROUGH
THE END OF THE WEEK. WILL LEAN TOWARD THE WEAKER CONSENSUS AT THIS
POINT...BUT THE CURRENT THINKING IS THAT THE ECMWF IS TOO
WEAK...AND THUS WILL LEAN TOWARD THE 00Z GFS AS A COMPROMISE.
CONFIDENCE IS LIMITED GIVEN THE MODEL SPREAD.


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

PREFERENCE: PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY

THE 00Z NAM TAKES T.D. EIGHT FARTHER WEST THAN THE MULTI-MODEL
CONSENSUS AND THE LATEST NHC TRACK. THE 00Z GFS AND 12Z ECMWF ARE
CLOSEST TO THE NHC TRACK THROUGH WED. THE 12Z CMC IS A BIT DEEPER
THAN THE NAM/GFS/ECMWF SOLUTIONS...BUT THE 12Z UKMET IS BY FAR A
DEEP OUTLIER. ALL OF THE MODELS INDICATE RECURVATURE OF T.D. EIGHT
BEGINNING ON WED. 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

A CONSENSUS OF THE 00Z NAM AND 12Z ECMWF ARE THE CLOSEST TO THE
LATEST NHC TRACK WITH T.D. NINE. THE 00Z GFS IS A LITTLE SLOWER
AND ALSO WEAKER WITH THIS SYSTEM BY COMPARISON. THE 12Z CMC IS A
SLOW OUTLIER...WITH THE 12Z UKMET LIKELY A DEEP OUTLIER. PLEASE
CONSULT THE LATEST NHC FORECAST ADVISORY FOR MORE INFORMATION ON
T.D. NINE.

ORRISON

...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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