Prognostic Meteorological Discussion
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000
FXUS10 KWNH 201700
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1155 AM EST MON FEB 20 2017

VALID FEB 20/1200 UTC THRU FEB 24/0000 UTC

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

12Z NAM/GFS MODEL EVALUATION...INCLUDING PRELIMINARY PREFERENCES

...SHORTWAVE CROSSING THE NORTHERN PLAINS/UPPER MIDWEST...
...UPPER TROUGH OVER THE HIGH PLAINS EJECTING NORTHEAST THROUGH
TONIGHT...
...SURFACE LOW PRESSURE/COLD FRONT CROSSING THE PLAINS/MIDWEST
THROUGH TUESDAY...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

LATE MORNING IR/WV SATELLITE IMAGERY SHOWING A FULL LATITUDE
TROUGH PUSHING E-NE ACROSS THE HIGH PLAINS IN THE LEE OF THE
ROCKIES. THIS ENERGY...FEATURING SEVERAL EMBEDDED WEAK
PERTURBATIONS...WILL CONTINUE TO EJECT EAST TOWARD THE MISSOURI
RIVER VALLEY AND THE UPPER MIDWEST THIS EVENING...AND INTO THE
GREAT LAKES AND EVENTUALLY HUDSON BAY BY MIDWEEK. THE EVOLUTION OF
THE SOUTHERN PORTION OF THIS FEATURE IMPACTING THE GULF COAST
REGION IS MENTIONED BELOW. AS THE SYSTEM EJECTS NE THROUGH
MIDWEEK...SURFACE LOW PRESSURE AND ITS ATTENDANT SURFACE COLD
FRONT WILL SWEEP ACROSS THE UPPER MIDWEST TONIGHT...CROSSING THE
GREAT LAKES AND OHIO VALLEY TUESDAY AND TUESDAY NIGHT. THE 12Z NAM
HAS TRENDED A BIT TOWARD THE REST OF AVAILABLE GUIDANCE WITH
RESPECT TO A MORE PROGRESSIVE EVOLUTION WITH THE EJECTING
SHORTWAVE...WHICH RESULTS IN A QUICKER FRONTAL PASSAGE.
HOWEVER...THE 12Z NAM REMAINS SOLIDLY ON THE SLOW SIDE OF THE
GUIDANCE ENVELOPE WITH THIS FEATURE TOWARD THE END OF THE PERIOD
AND WILL THEREFORE CONTINUE TO BE DISCOUNTED FOR NOW. THE GOOD
NEWS IS THAT GIVEN AGREEMENT OF THE REMAINING MODELS WITH THIS
FEATURE...AND THEIR MASS FIELDS...FORECAST CONFIDENCE IS BOLSTERED
A BIT MORE. WHILE THE NAM IS NOW MUCH MORE USABLE IN THE NEAR
TERM...WILL CONTINUE A NON-NAM SOLUTION AT ABOVE AVERAGE
CONFIDENCE.

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

PREFERENCE: 00Z UKMET/ECMWF / 12Z GFS
CONFIDENCE: AVERAGE

SOUTHERN HALF OF FULL LATITUDE TROUGH SLIDES ACROSS THE SOUTHERN
PLAINS TOWARD THE LOWER MISSISSIPPI VALLEY THROUGH TONIGHT....AND
EVENTUALLY CUTS OFF FROM UPPER FLOW...DEVELOPING A CLOSED LOW OVER
THE WEST CENTRAL GULF COAST BY MIDWEEK. THERE REMAINS SOME SPREAD
WITH THE CLOSED LOW EVOLUTION THAT IMPACTS THE REGION THROUGH
THURSDAY...BUT THERE HAS BEEN SOME CONVERGENCE BETWEEN THE
RESPECTIVE SOLUTIONS OF THE GFS AND THE 00Z UKMET/ECMWF. THE
NAM...PREVIOUSLY SOUTH NEAR 25N/90W WITH THE CLOSED LOW TUESDAY
NIGHT... HAS TRENDED BACK NORTH TOWARD THE REST OF GUIDANCE WITH
12Z RUN. THE 12Z GFS NUDGED NORTH AS WELL AND IS IN REASONABLY
GOOD AGREEMENT WITH THE 00Z ECMWF/ECENS. THE 00Z UKMET IS IN GOOD
ALIGNMENT AS WELL FOR TE MOST PART...BUT REMAINS A BIT STRONGER
WITH THIS FEATURE BY THE END OF THE PERIOD. THE 00Z CMC IS A BIT
FASTER AND SOMEWHAT WEAKER AND WILL BE DISCOUNTED FOR NOW...WITH
THE GFS/ECMWF/UKMET SOLUTION CLUSTERING WELL WITH ENSEMBLE
SPAGHETTI HEIGHTS. WILL USE A BLEND AROUND THE 00Z ECMWF/UKMET
ALONG WITH THE NEW 12Z GFS AT AVERAGE CONFIDENCE.

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

PREFERENCE: 00Z UKMET/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 TONIGHT. ONCE
AGAIN THE 12Z NAM...PREVIOUSLY A SLOW OUTLIER...HAS TRENDED TOWARD
THE MIDDLE OF THE GUIDANCE ENVELOPE. IN THIS CASE...THE 12Z
GFS...ALONG WITH THE 00Z UKMET/ECMWF CLUSTERED IN BETWEEN...AND
SHUNT THIS FEATURE QUICKLY NE TOWARD THE NORTHERN ROCKIES TUE
NIGHT...AND OVER THE NORTHERN PLAINS BY WED. THE ASSOCIATED
SURFACE LOW QUICKLY SCOOTS ACROSS THE UPPER MIDWEST THROUGH THE
DAY WED...BEFORE QUICKLY DEEPENING OVER THE UPPER GREAT LAKES/SE
ONTARIO ON THURSDAY. THE 12Z NAM...WHILE FASTER AND NOT QUITE AS
DEEP WITH THE SURFACE LOW...REMAINS ON THE SLOW SIDE OF AVAILABLE
GUIDANCE WITH THIS FEATURE...WITH THE 00Z CMC REMAINING A
PROGRESSIVE OUTLIER. BY THE END OF THE PERIOD...THE 12Z GFS AGAIN
IS ON THE FAST SIDE OF THE GUIDANCE ENVELOPE...EVEN CATCHING UP TO
THE FASTER CMC BY THURSDAY NIGHT. THE UKMET/ECMWF SOLUTION MESHES
WELL WITH ENSEMBLE SPAGHETTI HEIGHTS...AND ITS SURFACE LOW
LOCATION CLUSTERS WELL WITH THE ENSEMBLES. PENDING ARRIVAL OF THE
REMAINDER OF THE 12Z SUITE...WILL STICK WITH THE ECMWF/UKMET BLEND
AT AVERAGE CONFIDENCE.


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

PREFERENCE: 00Z ECMWF/ECENS MEAN / 12Z GFS/06Z GEFS MEAN
CONFIDENCE: AVERAGE

A LONGWAVE TROUGH WILL FINALLY BEGIN TO DROP SOUTHEAST ACROSS THE
WEST COAST ON WED...MOVING INLAND AND TRAVERSING THE INTERMOUNTAIN
WEST BY THURSDAY. 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 12Z NAM REMAINS
DEEPER/SHARPER WITH THE TROUGH AS IT ARRIVES OVER THE WEST ON
WEDNESDAY WITH THE 12Z GFS...ALONG WITH THE 00Z UKMET AND 00Z
ECMWF A LITTLE FLATTER. THE 12Z GFS HAS INCREMENTALLY TRENDED
TOWARD THE MORE AMPLIFIED ECMWF IDEA WITH ITS HEIGHT FALLS OVER
THE INTERMOUNTAIN REGION BY WEDNESDAY NIGHT/THURSDAY. THE LATEST
06Z/GEFS MEAN FAVORS THE FLATTER DETERMINISTIC GFS...AND IS A
DECENT MIDDLE GROUND BETWEEN THE 00Z ECMWF AND THE NEW 12Z GFS.
THE ECENS MEAN IS CLOSER TO THE MODEL CONSENSUS AS WELL AND WORKS
WELL IN A BLEND WITH THE ECMWF/GFS. WILL GO WITH A BLEND WEIGHTED
TOWARDS THE ECMWF AND ITS ENSEMBLE MEAN...WITH SOME 12Z GFS/06Z
GEFS MIXED IN TO REFLECT CONVERGING SOLUTIONS AT THE END OF THE
PERIOD.

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

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

MONTEFUSCO

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