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253
FXUS10 KWNH 270500
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 AM EDT MON MAR 27 2017

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

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

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

...WEAKENING UPPER LOW CROSSING INTO NORTHEAST THROUGH MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN VERY GOOD AGREEMENT WITH THIS SYSTEM...WITH THE
EXCEPTION OF THE 12Z CMC WHICH IS NOTABLY WEAKER COMPARED TO THE
OTHERWISE WELL CLUSTERED GUIDANCE. A NON-CMC CONSENSUS WILL BE
PREFERRED.


...NORTHERN STREAM TROUGH CROSSING THE UPPER MIDWEST THROUGH MON...
...ENERGY CROSSING SOUTHEAST CANADA THROUGH TUES/WED...
...UPPER TROUGH OVER THE CNTRL PLAINS WEAKENING INTO THE OH
VALLEY/NORTHEAST MON NIGHT/TUES...
...POSSIBLE SHORTWAVE PHASING OVER NEW ENGLAND BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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

A NORTHERN STREAM TROUGH EXITING THE NORTHERN PLAINS WILL CROSS
THE UPPER MIDWEST THROUGH MON AND THEN MOVE DOWNSTREAM ACROSS
SOUTHEAST CANADA WHERE IT WILL BEGIN TO AMPLIFY. MEANWHILE...A
SOUTHERN STREAM CLOSED LOW AND ASSOCIATED UPPER TROUGH APPROACHING
THE MID MS VALLEY WILL GRADUALLY WEAKEN THROUGH THE PERIOD AS IT
APPROACHES THE OH VALLEY AND THEN MOVES INTO THE NORTHEAST. THIS
WILL ALLOW SURFACE LOW PRESSURE TO ALSO LIFT NORTHEAST ACROSS THE
AREA. THE NORTHERN STREAM ENERGY BY TUES AND WED IS EXPECTED TO
BECOME DOMINANT AND THERE IS EXPECTED TO BE A DEEP LAYER LOW
CENTER EVOLVING NEAR NOVA SCOTIA BY EARLY THURS. PREVIOUS MODEL
CYCLES HAD HINTED AT SOME POTENTIAL FOR PHASING NORTHERN AND
SOUTHERN STREAM SHORTWAVES NEAR ENGLAND...WITH PREVIOUS GFS RUNS
IN PARTICULAR DOING THIS...BUT COLLECTIVELY THE MODELS HAVE NOW
COME INTO AGREEMENT ON LITTLE TO NO PHASING AS THE SOUTHERN ENERGY
DAMPENS OUT AND THE SURFACE LOW TRACKS A LITTLE FARTHER SOUTH AND
EAST BEFORE GETTING CAUGHT BY THE STRONGER NORTHERN STREAM ENERGY.
THE 00Z GFS AND 12Z UKMET TEND TO BE A LITTLE FASTER WITH THE
SOUTHERN STREAM SURFACE WAVE...WITH THE 00Z NAM AND 12Z CMC THE
SLOWEST. THE 12Z ECMWF SPLITS THE DIFFERENCE. WILL PREFER A SLIGHT
HEDGE TOWARD THE MORE PROGRESSIVE CONSENSUS SINCE THE SOUTHERN
STREAM ENERGY WILL BE QUICKLY DAMPENING OUT...SO WILL PREFER A
GFS/UKMET/ECMWF BLEND AT THIS POINT.


...WEAKER NORTHERN STREAM TROUGH OVER THE NORTHWEST MON/TUES...
...STRONG CLOSED LOW EVOLUTION INTO THE SOUTHWEST MON/TUES...
...EJECTING INTO THE CNTRL/SOUTHERN PLAINS WED/THURS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z UKMET AND 12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

ON MON AND TUES...THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE
DEVELOPMENT OF A RATHER STRONG UPPER TROUGH AND ASSOCIATED CLOSED
LOW THAT WILL DROP DOWN THROUGH THE SOUTHWEST AND INTO THE FOUR
CORNERS REGION. THE HEIGHT FALLS WILL BE ENCROACHING ON THE
SOUTHERN HIGH PLAINS BY WED AND THEN THE LOWER MS VALLEY ON THURS
ALONG WITH A WELL-DEFINED LOW PRESSURE CENTER. MEANWHILE...THE
MODELS SHOW A WEAKER NORTHERN STREAM COMPONENT OF THE ORIGINAL
TROUGH CROSSING THE NORTHWEST U.S. AND EJECTING OUT INTO THE
NORTHERN HIGH PLAINS BY TUES AND WED.

THE 00Z NAM EVENTUALLY GETS TO BE A LITTLE SLOW WITH THE SOUTHERN
STREAM HEIGHT FALLS COMPARED TO THE BETTER CLUSTERED 00Z GFS AND
THE 12Z NON-NCEP MODEL SUITE. THE NAM ALSO HAS THE FOCUS OF ITS
HEIGHT FALLS A LITTLE FARTHER SOUTH COMPARED TO THE MODEL
CONSENSUS. THE 00Z GFS THOUGH AT THE SURFACE APPEARS TO BE
FOCUSING A BIT TOO MUCH LOW PRESSURE TOO FAR NORTH TOWARD THE
CENTRAL HIGH PLAINS ON WED. ALTHOUGH BY THURS IT COMES INTO MUCH
BETTER AGREEMENT WITH THE MODEL CONSENSUS. GENERALLY THE STRONGEST
MODEL CLUSTERING FOR THE PERIOD RESIDES WITH THE 12Z UKMET AND 12Z
ECMWF.


...COLD FRONT WEAKENING INTO BRITISH COLUMBIA ON TUES...
...ONSHORE FLOW INTO THE PACIFIC NORTHWEST THROUGH TUES NIGHT...
...LOW PRESSURE ENTERING BRITISH COLUMBIA...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF
CONFIDENCE: AVERAGE

RELATIVELY MODEST SPREAD IS NOTED WITH THIS NEXT SYSTEM...BUT
GENERALLY THE STRONGER MODEL CLUSTERING RESIDES WITH THE 00Z GFS
AND 12Z ECMWF. THE 00Z NAM APPEARS A TAD TOO PROGRESSIVE WITH THE
LOW CENTER...THE 12Z UKMET TOO SLOW...AND THE 12Z CMC TOO FAR
NORTH. GIVEN THE GFS/ECMWF CLUSTERING AND ENSEMBLE SUPPORT...A
GFS/ECMWF BLEND WILL BE PREFERRED.


...SHORTWAVE/SURFACE LOW NEAR THE PACIFIC NORTHWEST BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z UKMET AND 12Z ECMWF
CONFIDENCE: AVERAGE

THE 00Z GFS APPEARS TOO AMPLIFIED WITH A SHORTWAVE APPROACHING THE
PACIFIC NORTHWEST GIVEN A LACK OF SUPPORT FROM THE REMAINING
GUIDANCE AND ALSO THE ENSEMBLE MEANS. THE 00Z NAM MAY BE A TAD TOO
PROGRESSIVE AS IT BECOMES THE MOST PROGRESSIVE SOLUTION. THE 12Z
CMC IS OVERALL THE SLOWEST...WITH THE 12Z UKMET AND 12Z ECMWF IN
BETWEEN SLOWER AND FASTER CAMPS. WILL PREFER THE UKMET/ECMWF
CLUSTER AS IT IS CLOSEST TO THE MODEL CONSENSUS.


...VIGOROUS TROUGH DIGGING INTO THE WEST ON THURS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS AGREE IN DIGGING A STRONG UPPER TROUGH INTO THE WESTERN
U.S. ON THURS. THE MODELS ARE ACTUALLY WELL CLUSTERED WITH TIMING
AND DEPTH THROUGH EARLY THURS WITH EXCEPTION TO THE 12Z UKMET
WHICH IS STRONGER WITH ENERGY DIGGING INTO THE BASE OF THE UPPER
TROUGH. A NON-UKMET CONSENSUS WILL BE PREFERRED AT THIS TIME.


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

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

ORRISON

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