Prognostic Meteorological Discussion
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FXUS10 KWNH 200648
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 AM EST MON FEB 20 2017

VALID FEB 20/0000 UTC THRU FEB 23/1200 UTC

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

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

...CLOSED LOW DEVELOPMENT NEAR NORTHERN NEW ENGLAND/NOVA SCOTIA
THROUGH MON...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM THROUGH MON...SO
WILL PREFER A GENERAL MODEL COMPROMISE.


...SHORTWAVE CROSSING OUT INTO THE NORTHERN PLAINS...
...UPPER TROUGH EJECTING OUT OF THE SOUTHWEST INTO THE PLAINS...
...ENERGY REACHING THE UPPER MIDWEST MON NIGHT...
...SURFACE LOW PRESSURE/COLD FRONT CROSSING THE PLAINS/MIDWEST
THROUGH TUES...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

A NORTHERN STREAM TROUGH EJECTING OUT ACROSS THE NORTHERN PLAINS
ON MON COUPLED WITH THE NORTHERN PORTION OF THE SOUTHERN STREAM
TROUGH EJECTING OUT OF THE SOUTHWEST WILL WORK IN TANDEM TO DRIVE
LOW PRESSURE ACROSS THE DAKOTAS EARLY MON AND THEN UP TOWARD
HUDSON BAY ON TUES AS A TRAILING COLD FRONT CROSSES THE
PLAINS/MIDWEST AND GREAT LAKES. THE 00Z NAM BECOMES A BIT SLOWER
THAN THE MODEL CONSENSUS WITH THE ENERGY IN THE SOUTHERN STREAM
THAT GETS PULLED NORTHEAST IN TANDEM WITH THE NORTHERN STREAM
TROUGH AND ENDS UP WITH A SLOWER FRONTAL PROGRESSION. THE
REMAINING MODELS ARE REASONABLY WELL CLUSTERED... WITH THEIR MASS
FIELDS...AND SO WILL PREFER A NON-NAM CONSENSUS.


...SHORTWAVE/SURFACE LOW APPROACHING CROSSING THE WEST COAST ON
MON...

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

THE 00Z NAM AND TO A LESSER EXTENT THE MORE INCONSISTENT 00Z CMC
ARE A TAD SLOWER WITH THE SHORTWAVE/SURFACE LOW ARRIVING EARLY MON
ACROSS WESTERN OREGON COMPARED TO THE WELL-CLUSTERED 00Z GFS/00Z
UKMET AND 00Z ECMWF. WILL KEEP CONTINUITY AND CONTINUE FAVORING
THE GFS/UKMET/ECMWF CAMP.


...SHORTWAVE/SURFACE LOW CROSSING THE WEST COAST MON NIGHT/EARLY
TUES...
...SURFACE LOW REACHING THE NORTHERN PLAINS/UPPER MIDWEST BY WED...
...SURFACE LOW/COLD FRONT CROSSING THE GREAT LAKES BY THURS...

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

THE 00Z CMC IS THE MOST PROGRESSIVE WITH THE NEXT IN A SERIES OF
SHORTWAVE/SURFACE LOWS THAT IMPACT THE WEST COAST BY MON NIGHT AND
EARLY TUES. THE 00Z NAM ON THE OTHER HAND IS THE SLOWEST
SOLUTION...WITH THE 00Z GFS/00Z UKMET AND 00Z ECMWF CLUSTERED IN
BETWEEN. THE MODELS TAKE THIS ENERGY QUICKLY INLAND AND OUT INTO
THE NORTHERN PLAINS BY WED WITH A PROGRESSIVE SURFACE LOW THAT
THEN TRAVELS ACROSS THE UPPER MIDWEST THROUGH WED. BY THURS...THIS
SURFACE LOW WILL BE DEEPENING WHILE CROSSING THE GREAT LAKES
REGION AS TRAILING COLD FRONT APPROACHES THE OH VALLEY. THROUGH
THE LATER STAGES OF THE PERIOD...THE 00Z CMC REMAINS A PROGRESSIVE
OUTLIER...WITH THE 00Z NAM SLOWER AND TOO DEEP OVER THE GREAT
LAKES. BY WED AND THURS...THE 00Z GFS BEGINS TO OUTRUN THE MODEL
CONSENSUS AND CATCHES UP TO THE FASTER CMC. WILL PREFER TO GO A
LITTLE SLOWER THAN THE GFS...AND LEAN TOWARD THE UKMET/ECMWF CAMP
AT THIS TIME.


...LONGWAVE TROUGH FINALLY REACHING THE WEST COAST BY WED...
...LOW PRESSURE DEVELOPING OVER THE CENTRAL/SOUTHERN HIGH PLAINS...

PREFERENCE: BLEND OF THE 00Z ECMWF AND 12Z ECENS MEAN
CONFIDENCE: AVERAGE

A LONGWAVE TROUGH WILL MOVING ACROSS THE WEST COAST ON WED AND
BEGIN TRAVERSING THE INTERMOUNTAIN REGION. THIS WILL LEAD TO AN
ELONGATED AREA OF LOW PRESSURE DEVELOPING OVER THE CENTRAL AND
SOUTHERN HIGH PLAINS ALONG A FRONTAL ZONE EAST OF THE ROCKIES. THE
00Z NAM AND 00Z CMC TEND TO BE PERHAPS A LITTLE DEEPER/SHARPER
WITH THE TROUGH AS IT ARRIVES OVER THE WEST WITH THE 00Z GFS/00Z
UKMET AND 00Z ECMWF A LITTLE FLATTER. HOWEVER BY THE END OF THE
PERIOD...THE 00Z GFS IS THE FLATTEST SOLUTION WITH ITS HEIGHT
FALLS OVER THE INTERMOUNTAIN REGION...AND BY THEN THE 00Z CMC IS
THE SHARPEST. CONSEQUENTLY...THE 00Z GFS IS A BIT WEAKER BY EARLY
THURS WITH ITS LEE-SIDE CYCLOGENESIS. THERE IS A BIT OF A TREND
TOWARD HAVING A SOMEWHAT SLOWER AND PERHAPS DEEPER TROUGH OVER THE
INTERMOUNTAIN WEST BY THURS. IN FACT...THE 00Z UKMET HAS SLOWED TO
THE POINT OF BEING THE SLOWEST SOLUTION AT THE END OF THE PERIOD.
THE LATEST GEFS MEAN FAVORS THE FLATTER DETERMINISTIC GFS...BUT
THE ECENS MEAN IS CLOSER TO THE MODEL CONSENSUS AND THE
DETERMINISTIC ECMWF AS WELL. WILL FAVOR A BLEND OF THE 00Z ECMWF
AND 12Z ECENS MEAN AT THIS POINT.


...SOUTHERN STREAM TROUGH/CLOSED LOW EVOLUTION NEAR THE GULF
COAST...

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

THERE REMAINS SOME SPREAD WITH THE CLOSED LOW EVOLUTION THAT
IMPACTS THE WESTERN AND CENTRAL GULF COAST AREA TUES THROUGH
THURS...BUT THERE HAS BEEN SOME CONVERGENCE BETWEEN THE 00Z
GFS/00Z UKMET AND 00Z ECMWF. THE 00Z NAM IS A BIT SLOWER AND SOUTH
OF THIS CONSENSUS...WITH THE 00Z CMC A BIT FASTER AND SOMEWHAT
WEAKER. WILL LEAN TOWARD THE GFS/UKMET/ECMWF CAMP AT THIS POINT.

www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





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