Prognostic Meteorological Discussion
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789
FXUS10 KWNH 090459
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1158 PM EST MON FEB 08 2016

VALID FEB 09/0000 UTC THRU FEB 12/1200 UTC

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

00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

LONGWAVE TROF ACROSS THE EASTERN THIRD OF THE U.S LIFTING OUT BY
WED
ASSOCIATED SURFACE LOWS OVER THE E GREAT LAKES/THE MID-ATLANTIC
COAST TUESDAY/WEAK LOW S OF LONG ISLAND WED MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS AND 12Z ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

LARGE SCALE DIFFERENCES ARE CONTINUING TO BECOME BETTER RESOLVED
WITH AN OVERALL MODEL AGREEMENT THROUGH THE TROF`S EVOLUTION
INCLUDING ITS FILLING AND LIFTING NORTHEASTWARD BY THE END OF THE
FORECAST PERIOD.  THE 12Z CMC IS THE ONLY MAJOR OUTLIER IN THIS
RESPECT FILLING A BIT QUICKER THAN THE REST OF THE GUIDANCE
INCLUDING THE 18Z GEFS AND 12Z ECENS ENSEMBLE SPREAD BUT NOT
SIGNIFICANTLY SO TO DISREGARD IT.   THE DIFFERENCES REMAIN TIED TO
INTERNAL WAVE TIMING/STRENGTH DIFFERENCES BUT EVEN THESE ARE
STARTING TO COME TO BETTER AGREEMENT.  THE SIGNIFICANT DIFFERENCES
APPEAR MOSTLY WITH RESPECT TO THE INITIAL COASTAL DEVELOPMENT
EXITING THE VA COAST THIS MORNING...WITH THE 00Z NAM/12Z CMC AND
12Z UKMET DEVELOPING INITIALLY EAST AND SOUTH OF FAIRLY STRONG
GEFS/ECENS SURFACE CLUSTER (THE CMCE CLUSTER DOES SUPPORT THESE
SOLUTIONS - BUT EVEN THE OPERATIONAL IS ON THE SE SIDE OF THAT
CLUSTER).  THE ECMWF MEMBERS COMPOSE THE MAJORITY OF THE WESTERN
MEMBERS THOUGH THE OPERATIONAL IS ON THE EAST SIDE OF THOSE
MEMBERS VERY CLOSE TO THE GFS AND GEFS MEMBERS.  THE 12Z UKMET IS
CLOSER TO THE GFS/ECMWF AND ALSO DEVELOPS IN A SIMILAR MANNER AND
TIMING/STRENGTH COMPARED TO THE WEAKER CMC/NAM SOLUTIONS.  SOME OF
THESE DIFFERENCES LEAK INTO THE TRAILING PRESSURE TROF AND
SUBSEQUENT CYCLOGENESIS SOUTH (EAST) OF LONG ISLAND WED MORNING
WITH THE ECMWF WEAKEST AND SLOWEST TO DEVELOP THIS LOW ALSO BEING
ON THE SOUTHERN PACKING BUT WITHIN PROXIMITY TO THE GFS.  MODELS
ARE ALL IN STRONG AGREEMENT WITH THE LINGERING SURFACE LOW ACROSS
THE GREAT LAKES INTO NEW ENGLAND THROUGH WED NIGHT/THUR MORNING.
COULD SUPPORT A NON-CMC BLEND OVERALL BUT WITH TIGHT AGREEMENT IN
TIMING/PLACEMENT AND FOR THE MOST PART STRENGTH OF ALL MAIN
FEATURES...WILL SUPPORT THE GFS/ECMWF/UKMET BLEND THAT IS STRONGLY
SUPPORTED BY THE 18Z GEFS/12Z ECENS MEAN PACKING.  CONFIDENCE IS
SLIGHTLY ABOVE AVERAGE IN THIS BLEND.


ARCTIC CUT-OFF/COLD SURGE ENTERING THE NORTHERN GREAT
LAKES/ARROWHEAD OF MN FRI MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

IN THE WAKE OF THE FILLING LARGE SCALE TROF ACROSS THE EASTERN
U.S...A STRONG WAVE IS DEEPENING ACROSS THE NORTH POLE TODAY WHICH
WILL DROP SOUTH AND DEEPEN THE ARCTIC VORTEX BUILDING A DEEP POOL
OF ARCTIC COLD ACROSS HUDSON BAY THURS AND JAMES BAY BY FRIDAY
MORNING.  OVERALL THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE
TIMING OF THE WAVE.  THE 12Z CMC IS MOST OUT OF PHASE WITHIN THE
LARGE SCALE ENSEMBLE SPAGHETTI PLOT...THIS IS CONTRIBUTED TO A FEW
FACTORS.  IT IS THE DEEPEST LOW (ALMOST 60 DM MORE THAN THE
REST/CONSENSUS) CONTRIBUTED BY THE COLDEST OF THE GUIDANCE THOUGH
ALSO IS QUITE BROAD WITH THAT COLD POOL WEST TO EAST --- THIS
ALLOWS FOR A BROADER UPPER LEVEL WAVE EXTENDING WEST TO LAG ACROSS
BOREAL CANADA COMPARED TO THE OTHER GUIDANCE. THOUGH THE 12Z
ECMWF/UKMET ARE ALSO SLIGHTLY WEST COMPARED TO THE 00Z NAM/GFS
WITH RESPECT TO THE INNER CORE OF THE UPPER LOW AND COLD
POOL;THOUGH THE 00Z GFS ALSO DID TREND A BIT EAST OF THE 12Z/18Z
GEFS INCREASING SPACING WITH THE ECMWF/UKMET BY THE END OF THE
FORECAST PERIOD...IT IS NOT LARGE ENOUGH TO FAVOR ON CAMP OVER THE
OTHER.  MAINLY DUE TO THE DIFFERENCES IN DEPTH/SHAPE OF THE UPPER
LOW...WILL FAVOR A NON-CMC BLEND AND WITH OVERALL SMALL SPREAD
CONFIDENCE IS FAIRLY HIGH...SLIGHTLY ABOVE AVERAGE.


WEAK LOW PRESSURE MOVING FROM MONTANA TO TEXAS WED-THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-ECMWF BLEND
CONFIDENCE: AVERAGE

THE 12Z ECMWF SHIFTED FASTER AND IS REMAINS GENERALLY WEAKER AND
WEST COMPARED TO THE REST OF THE GUIDANCE AND THOUGH THE 12Z ECENS
MEAN TRENDED THIS WAY TOO...IT WAS NOT AS DRAMATIC AND IS CLOSER
PACKED TO THE 12Z CMC/00Z NAM/GFS/UKMET AT THE SURFACE. THE 12Z
CMC IS STRONGER WITH THE WAVE AND HAS IS A BIT MORE ROBUST IN
MOISTURE AND THEREFORE ASSOCIATED QPF SWATH OUT OF SASKATCHEWAN
INTO THE NORTH RED RIVER VALLEY AND ALSO LINGERS INTO THE OH/MS/TN
RIVER CONFLUENCE AREA. THE 12Z UKMET IS TIMED A BIT FASTER ALOFT
THAN THE GFS/NAM/CMC BUT TRACKS WELL WITH AT THE SURFACE AND
WITHIN THE QPF AXIS.  THE 00Z GFS REMAINS QUITE CONSISTENT RUN TO
RUN THOUGH DID SHIFT SLIGHTLY TO A DEEPER AND EASTWARD TRACK AT
THE SURFACE LIKE THE 12Z CMC...AND AS SUCH WILL FAVOR WITH SUPPORT
OF THE GEFS A NON-ECMWF BLEND AT AVERAGE CONFIDENCE.


DUAL SHORTWAVE PACK GLANCING THE PACIFIC NORTHWEST WED
DEEPER LARGE SCALE TROF APPROACHING LATE FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE LARGE SCALE RIDGE IS WELL LOCKED INTO THE WESTERN US WHICH IS
FORCING THE PROGRESSIVE SHORTWAVES DANCING ALONG THE OUTER
PERIPHERY OF LARGE SCALE UPPER CYCLONE OVER THE NORTHERN PACIFIC
CURRENTLY.  THE LEAD WAVE WITHIN THE CYCLONE ALONG 140W IS IN
FAIRLY GOOD AGREEMENT IN TIMING DEPTH/INCLUDING THE LINGERING
CENTER THAT WILL SHEAR COMING ASHORE WED MORNING; THOUGH SPACING
WITH THE UPSTREAM KICKER IS A BIT DIFFERENT.  THE GFS IS THE MOST
REDUCED IN SPACING ALONG WITH THE 12Z UKMET WHICH IS ALSO QUITE
WRAPPED UP COMPARED TO THE CMC/ECMWF/NAM.  OVERALL AFFECTS ARE
MINOR EXCEPT OVER THE OCEAN AND GENERAL WEAKENING OF THE TOP OF
THE RIDGE...ALLOWING FOR THE ONSHORE SW ORIENTED MOISTURE FEED.
THE NEXT S/W MOVING THROUGH IS THEREFORE FASTER IN THE GFS/UKMET
BRINGING QPF TO THE NW NEARLY 6-12 HRS FASTER THAN THE SLOWER
ECMWF.  AT THIS POINT...THE GFS/UKMET RETAINED ENERGY UPSTREAM
WHICH SUPPORTS A MORE AMPLIFIED WAVE THAN THE 12Z ECMWF WHICH
PHASED THE WAVE WITH THE UPSTREAM ENERGY MAKING IT A BIT FASTER
AND LESS AMPLIFIED BY THE END OF THE FORECAST PERIOD THAN THE
GFS/GEFS.  THOUGH THE 00Z GFS DID TREND A BIT FASTER...THIS WOULD
SUPPORT MORE TOWARD THE ECMWF SOLUTION. THE 00Z NAM REMAINED IN
STRONG AGREEMENT WITH THE ECMWF TO SUPPORT A BLEND.  CONFIDENCE IS
GENERALLY LOW GIVEN THE SPREAD IN TIMING TOWARD THE END OF THE
PERIOD AND SLIGHT BUT INCREASING DIFFERENCE SEEN BETWEEN THE
OPERATIONAL ECMWF AND THE 12Z ECENS MEAN.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

GALLINA

$$





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