Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7
000
FXUS10 KWNH 100450
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1149 PM EST TUE FEB 09 2016

VALID FEB 10/0000 UTC THRU FEB 13/1200 UTC

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

00Z GUIDANCE EVALUATION INCLUDING FINAL 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/WEAK LOW SE OF CAPE
CAD ISLAND WED MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: AVERAGE

SYNOPTICALLY MODEL ARE IN GOOD AGREEMENT WITH SOME SMALL INTERNAL
DIFFERENCES IN TIMING/STRENGTH OF THE FEATURES.  IN THE WAKE OF
THE EXITING CYCLONE NEAR NOVA SCOTIA...A WEAK WAVE IS FORECAST TO
DEVELOP ALONG THE LINGERING FRONT.  THIS APPEARS TO BE THE
REMAINING LARGEST DIFFERENCE.  THE 00Z GFS/NAM ARE GENERALLY A BIT
STRONGER/FASTER WITH THE ENERGY SWINGING THROUGH NEW ENGLAND AS
WELL AS DRAWING SHORTWAVE ENERGY AROUND THE FILLING BASE OF THE
LARGER SCALE TROF OVER THE SOUTHERN APPALACHIANS AT THIS TIME...
WV LOOP SHOWS A WEAK BAROCLINIC LEAF ALREADY EMERGING TO SUPPORT
THIS DEVELOPMENT.  THE ENSEMBLE SPREAD WITH RESPECT TO THIS
CLUSTER IS ACTUALLY QUITE LARGE WEST TO EAST AT SUCH A SHORT TIME
FRAME DRIVEN MAINLY AS THE FEATURE IS VERY WEAK...AT LEAST THE
FRONTAL ZONE IS GENERALLY PLACED WELL.  THE 00Z GFS IS MOST
DRAMATIC WITH A LARGE SHIFT FASTER/EAST OF THE BEST CLUSTER WITH
THIS LOW.  THE 00Z NAM/12Z ECMWF ARE MORE CENTRALLY LOCATED WITH
THE 18Z GEFS/12Z ECENS MEAN...WHILE THE 12Z CMC/UKMET ARE MORE
STRUNG OUT AND PLACE MANY SMALLER WEAKER LOWS FROM THE HUDSON
CANYON THROUGH GEORGES BANK OCEANIC ZONES ON WED MORNING.  STILL
WILL FAVOR AN OPERATIONAL MODEL BLEND...BUT GIVEN THE SPREAD OF
THESE INTERNAL DIFFERENCES THAT WILL HAVE AFFECTS ON SENSIBLE
WEATHER CONFIDENCE IS ONLY AVERAGE ON THIS LARGER/ALL ENCOMPASSING
BLEND.


WEAK WAVE AND LOW MOVING ACROSS THE NORTHERN/CENTRAL PLAINS INTO
THE MS VALLEY WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

SMALL DIFFERENCES IN SURFACE LOW PLACEMENT EXIST TIME TO TIME
WITHIN THE OPERATIONAL MODEL SUITE BUT ADJUST BACK TO THE AVERAGE
WITH THE NEXT TIME STEP...ALL GENERALLY MINOR TO CONTINUE AN
OPERATIONAL MODEL CONSENSUS WITH THIS WAVE AT ABOVE AVERAGE
CONFIDENCE.


ARCTIC CUT-OFF/COLD SURGE ENTERING THE NORTHERN GREAT
LAKES/ARROWHEAD OF MN FRI MORNING AND ASSOCIATED SURFACE LOW
ACROSS SE ONTARIO/NEW ENGLAND SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND AFTER 12/12Z
CONFIDENCE: ABOVE AVERAGE

IN THE WAKE OF THE FILLING LARGE SCALE TROF ACROSS THE EASTERN
U.S...A STRONG WAVE DEEPENING ACROSS THE NORTH POLE 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 OVERALL
SETUP INVOLVING THIS ARCTIC UPPER LOW AND ARCTIC SURFACE HIGH
MOVING TOWARDS THE NORTHERN PLAINS INCLUDING TIGHTLY PACKED
ENSEMBLE MEMBERS AROUND THE SOLUTIONS...THIS INCLUDES A SLOWING OF
THE GFS/GEFS AND QUICKENING OF THE ECWMF/ECENS AS A WHOLE.   IF TO
BE VERY PICKY WITHIN THE OVERALL GUIDANCE...THE MODELS FOLLOW A
TRADITIONAL SETUP/BIAS...THE UKMET LEANS FORWARD/FASTER FOLLOWED
BY THE GFS THEN THE ECMWF WITH THE NAM AND CMC LAGGING THE MOST.
THE CMC`S LAG IS MOST DRAMATIC THOUGH BY FRIDAY EVENING/SAT
MORNING WHEN AN INTERNAL CORE VORT LOBE LAGS IT OWN MEAN HOLDING
UP THE INNER CORE AND RESOLVING TROUGHING OVER NE ONTARIO BUT ALSO
RESULTING IN A LAGGED SURFACE REFLECTION OVER THE GREAT LAKES/NEW
ENGLAND.  THIS LAG IS SUPPORTED ALOFT BY THE 00Z NAM BUT NOT DOES
NOT RESOLVE ITSELF IN THE LOWER LEVELS OR WITHIN 21Z
SREF...LEADING TO A BIT OF CONCERN IN USING IT IN THE BLEND.  AS
SUCH WILL FAVOR A NON-CMC BLEND PARTICULARLY AFTER 12/18Z AT ABOVE
AVERAGE CONFIDENCE GIVEN THIS IS QUITE SMALL DETAIL DIFFERENCE AT
DAY 3.


SHORTWAVE ENTERING PACIFIC NORTHWEST WEDNESDAY RAPIDLY DIVING
SOUTHEAST INTO THE BASE OF THE EAST COAST TROF INTO FRI AND
OFFSHORE EARLY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

SHORTWAVE ENERGY FROM THE BASE OF A NEGATIVE TILT TROF CURRENTLY
DEFINED IN WV NEAR 40N137W WILL GLANCE THE PACIFIC
NORTHWEST...SLIGHT TIMING DIFFERENCES WILL LEAD SPREAD WITH WHERE
THE ENERGY WILL BE DRAWN THROUGH THE LARGE SCALE RIDGING ACROSS
THE ROCKIES.  HOW AND WHERE WILL DETERMINE THE LENGTH AND STRENGTH
OF THE RESULTANT SHEARED SHORTWAVE THAT WILL RAPIDLY MOVE THROUGH
THE GREAT PLAINS AND CENTRAL MO RIVER VALLEY FRIDAY MORNING.
ADDITIONALLY...THIS WILL ALSO LEAD TO DIFFERENCES IN AMOUNT OF
INFLUENCE OR PHASING WITH THE BASE OF THE ARCTIC TROF DROPPING OUT
OF MANITOBA.  OBVIOUSLY THERE IS A POTENTIAL FOR LARGE SPREAD DUE
TO THE LENGTH/CONSOLIDATION OF THE SHEARED ENERGY AS WELL AS
STRENGTH...ALL OF WHICH PLAY A ROLE IN THE EVENTUAL COASTAL
SURFACE CYCLOGENESIS FRIDAY EVENING.  THE TREND IS FOR MORE ENERGY
TO BE SHED INTO THE RIDGE...WHICH HAS SEEN A GENERAL TREND TOWARD
A DEEPER SURFACE REFLECTION ON DAY 3 WITH AN INCREASE IN ENSEMBLE
MEMBERS DEVELOPING A CYCLONE AND A TREND TOWARD A DEEPER LOW AS
SEEN IN THE 00Z NAM/GFS AND 12Z UKMET/ECMWF.  THE 12Z CMC INJECTED
THE LEAST ENERGY AND WAS GENERALLY FASTER AND WEAKER
OVERALL...AWAY FROM THIS TREND.  THE 12Z ECMWF WAS SLOWEST AND
MORE PHASED ROUNDING THE BASE OF THE TROF FRIDAY INCREASING
DIVERGENCE ALOFT FOR BETTER/STRONGER SURFACE CYCLOGENESIS...AND IS
ON THE SOUTHEAST FRINGE OF THE 12Z ECENS MEAN AS WELL AS SOUTH OF
THE BETTER CLUSTERED UKMET/NAM/GFS...WHICH ARE TIGHT TO THE 18Z
GEFS MEAN AND THE OVERALL TREND.  STILL GIVEN ALL THE
DIFFERENCES/SPREAD POSSIBLE WITH JUST SUBTLE
TIMING/PLACEMENT/INJECTION DIFFERENCES UPSTREAM...THE ECMWF MAY BE
ON THE BEST TRAJECTORY AND NOT OUT OF THE REALM OF POSSIBILITIES.
AS SUCH WILL SUPPORT A NON-CMC BLEND AT AVERAGE CONFIDENCE.


DEEPER LARGE SCALE TROF APPROACHING NORTHWEST LATE FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/GFS AND 12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

RUN TO RUN ENSEMBLE SPAGHETTI PLOTS SHOW A SIGNIFICANT TREND AWAY
FROM A PRONOUNCED TROF ENTERING THE PACIFIC NORTHWEST FRIDAY INTO
SATURDAY BUT A FILLING ONE TRENDING FLATTER AND FASTER WITH EACH
12HR CYCLE.  THIS IS GENERALLY LEAD BY ECMWF OPERATIONAL LAGGED
SLIGHTLY BY THE ECENS MEAN.  THE GFS/GEFS WERE SLOWEST TO TREND
THIS WAY BUT HAVE CONSIDERABLY FLATTENED WITH TIME TO HAVE FAIRLY
GOOD AGREEMENT WITH THE CMCE/CMC UKMET AND NAM WITH THE 12Z CYCLE.
 HOWEVER THE 12Z ECMWF MAY BE A SHADE TOO AGGRESSIVE AS THE
LEADING PORTION OF THE WAVE IS VERY EFFECTIVE (PERHAPS TOO
EFFECTIVE) IN DAMPENING THE WELL ESTABLISHED WESTERN RIDGE
ALLOWING IT TO BE GENERALLY FAST ACROSS HIGH PLAINS IN LEE OF THE
NORTHERN ROCKIES WITH ASCENT/QPF.   ALL OTHER MODELS TO DAMPEN THE
RIDGE BUT ONLY THE 12Z CMC WAS AS AGGRESSIVE AS THE 12Z
ECMWF...THIS INCLUDES THE 12Z ECENS MEAN. THE 12Z UKMET IS MOST
AMPLIFIED BY THE END OF THE FORECAST PERIOD BUT QUICKLY MOVES OUT
OF PHASE WITH OTHER GUIDANCE INTO DAY 4 WITH A STRONGLY AMPLIFIED
TROF...MAKING IT LESS DESIRABLE.  THE 00Z GFS DID TREND A BIT MORE
AMPLIFIED WITH THE RIDGE BUT BRINGS THE KICKER/BACK EDGE OF THE
BROADER WAVE INTO THE NORTHWEST IN GOOD TIMING OF THE ECMWF.  THE
00Z NAM IS SIMILAR TO THE GFS BUT LESS AMPLIFIED.  THESE ARE
SUPPORTED BY THE GEFS.  TO BEST REPRESENT THESE MORE FAVORABLE
MEANS WILL BLEND THE 00Z NAM/GFS AND 12Z ECMWF AT AVERAGE
CONFIDENCE.


...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

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.