Prognostic Meteorological Discussion
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000
FXUS10 KWNH 270646
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 AM EDT WED AUG 27 2014

VALID AUG 27/0000 UTC THRU AUG 30/1200 UTC

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


00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE
ECMWF

...UPPER TROUGH AND ASSOCIATED COLD FRONT CROSSING THE NORTHEAST...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM IS A SLIGHTLY STRONG OUTLIER WITH THE DETAILS OF THE
UPR TROUGH CROSSING THE NORTHEAST AND MOVING OFFSHORE INTO THE
ATLANTIC OCEAN OVER THE NEXT COUPLE OF DAYS. AT THE SFC...THE NAM
APPEARS TO BE JUST A TAD SLOWER WITH THE ADVANCE OF ITS SFC COLD
FRONT. THE GLOBAL MODELS ARE WELL CLUSTERED OTHERWISE...AND SO
WILL PREFER A NON-NAM CONSENSUS.


...SHORTWAVE IMPULSE AND SURFACE LOW IMPACTING THE UPPER MIDWEST
BY THURS AND FRI...

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

LOW PRESSURE WILL BE DEVELOPING OVER THE CNTRL HIGH PLAINS BY LATE
WED AS SHORTWAVE ENERGY EJECTS OUT OF THE CNTRL ROCKIES. THIS LOW
CENTER SHOULD THEN EJECT NEWD TWD THE UPPER MIDWEST THROUGH THURS
AND THURS NIGHT. THE 00Z NAM AND 00Z GEM MAY BE A TAD TOO FAR TO
THE LEFT WITH THEIR LOW TRACKS RELATIVE TO THE GLOBAL MODEL
CONSENSUS. THE 00Z GFS/00Z ECMWF AND 00Z UKMET ARE SLIGHTLY MORE
SUPPRESSED AND THERE IS GENERAL ENSEMBLE AGREEMENT ON THAT
SCENARIO. WILL FAVOR A BLEND OF THE MORE SRLY LOW TRACK CAMP AS A
RESULT.


...UPPER-LEVEL TROUGH/LOW MOVING FROM THE ROCKIES IN THE PLAINS...
...SURFACE COLD FRONT DEVELOPING LATE WED IN THE LEE OF THE
CENTRAL ROCKIES...
...SURFACE LOW LIFTING INTO THE MIDWEST...

PREFERENCE: BLEND OF THE 00Z GFS/00Z GEM AND 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM AND 00Z GFS ARE IN REASONABLY GOOD AGREEMENT WITH THE
00Z UKMET/00Z GEM AND 00Z ECMWF IN HOW THEY HANDLE THE EVOLUTION
OF THE UPR LOW/TROUGH THAT EXITS THE ROCKIES OVER THE NEXT COUPLE
OF DAYS AND ADVANCES EAST ACROSS THE PLAINS AND TWD THE MIDWEST.
THE MODELS SHOW THAT A COLD FRONT WILL ADVANCE EAST AS WELL AND
THERE SHOULD BE A WAVE OF LOW PRESSURE THAT EVOLVES OVER THE
MIDWEST BY LATE FRI AND SAT. HOWEVER...THE 00Z NAM BECOMES A
FASTER AND WEAKER OUTLIER SOLN FROM 72 HRS ONWARD. THE 00Z UKMET
ALSO GRADUALLY BECOMES TOO WEAK. THE 00Z GFS/00Z GEM AND 00Z ECMWF
ARE IN VERY GOOD AGREEMENT WITH A SOMEWHAT STRONGER UPR
TROUGH/CLOSED LOW THAT TRAVERSES THE PLAINS. WILL PREFER A BLEND
OF THE GFS/GEM AND ECMWF AS A RESULT.


...EASTERLY WAVE ADVANCING WEST ALONG THE GULF COAST...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM IS A SLIGHTLY DEEPER OUTLIER WITH THIS SYS AS IT MOVES
INTO CNTRL/SRN TX OVER THE NEXT COUPLE OF DAYS. WILL PREFER A
NON-NAM CONSENSUS SOLN GIVEN SOLID GLOBAL MODEL AGREEMENT SEEN
OTHERWISE..


...NORTHERN STREAM TROUGH CLIPPING THE NORTHWESTERN U.S./CANADIAN
BORDER BY FRI...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

MODEL SPREAD WITH RESPECT TO THIS FEATURE HAS DIMINISHED...BUT THE
00Z NAM STILL APPEARS TO BE TOO STRONG ALOFT. THE REMAINING GLOBAL
MODELS FROM THE 00Z CYCLE ARE IN REASONABLY GOOD AGREEMENT. WILL
PREFER A NON-NAM CONSENSUS WITH THIS SYS.


...DEEP TROUGH DIGGING INTO THE NORTHWEST BY FRI AND SAT...

PREFERENCE: BLEND OF THE 00Z UKMET/00Z GEM AND 00Z ECMWF
CONFIDENCE: AVERAGE

THE 00Z GFS GRADUALLY BECOMES A SLIGHTLY FASTER OUTLIER WITH THE
NEXT TROUGH ARRIVING IN FROM THE PAC OCEAN FRI AND SAT. THE 00Z
NAM IS NOW JUST A TAD SLOWER THAN THE GLOBAL MODEL
CONSENSUS...WITH THE 00Z UKMET/00Z GEM AND 00Z ECMWF ALL WELL
CLUSTERED IN BETWEEN. WILL FAVOR A NON-NCEP CONSENSUS AS A RESULT.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





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