Prognostic Meteorological Discussion
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214
FXUS10 KWNH 230407
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1107 PM EST WED FEB 22 2017

VALID FEB 23/0000 UTC THRU FEB 26/1200 UTC

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

00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SOUTHERN STREAM CLOSED LOW FEATURE WEAKENING AND LINGERING OFF THE
SOUTHEAST COAST THROUGH EARLY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM HAS TRENDED POSITIVELY TO THE MEAN CLUSTER THE OTHER
DETERMINISTIC GUIDANCE.  WHILE THERE REMAINS SOME SMALL DETAIL
DIFFERENCES WITH TRADITIONAL FAST MEMBERS NAM/UKMET/GFS AND SLOWER
SOLUTIONS IN THE ECMWF/CMC WITH RESPECT TO THE WAVE AND SURFACE
LOW...THIS SEEMS MINOR AND A GENERAL MODEL BLEND SHOULD SUFFICE
WITH ABOVE AVERAGE CONFIDENCE.


SHORTWAVE LIFTING OUT OF NORTHERN ROCKIES INTO THE UPPER MIDWEST
WITH ASSOCIATED SURFACE LOW TRACKING ACROSS THE GREAT LAKES
TONIGHT AND CLIPPING N NEW ENGLAND THU NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

SMALL DEPTH ISSUES ARE NOTED WITH THE SHORTWAVE CROSSING OUT
THROUGH THE NORTHERN GREAT LAKES BUT TIMING LOOKS MUCH TIGHTER
CLUSTERED OVER THE LAST DAY.  THE 12Z CMC IS THE FLATTER SOLUTION
INITIALLY AND THE UKMET EVENTUALLY FLATTENS THE MOST BY FRI IN SE
CANADA BUT THIS DOES NOT SEEM TO AFFECT THE SURFACE AND LOWER
LEVEL WAVES AT 7H AND 850MB TO SUGGEST A GENERAL MODEL BLEND LOOKS
LIKE A GOOD SOLUTION AT HIGH CONFIDENCE.


BROAD LONGWAVE TROF CROSSING THE INTERMOUNTAIN WEST THU/FRI WITH
DEVELOPING CLOSED LOW AND SURFACE LOW OVER MIDWEST LATE FRI INTO
SAT...AND THROUGH THE CENTRAL GREAT LAKES INTO ONTARIO BY EARLY
SUN.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/GFS AND 12Z ECMWF BLEND
CONFIDENCE: AVERAGE

GOES-W WV DENOTES A WELL DEVELOPING WAVE OVER NE NV/SW ID
CURRENTLY AT THE LEADING EDGE OF THE BROADER LONGWAVE TROF OVER
THE WEST.  AS THIS LEADING WAVE ROLLS OUT OF THE NORTH CENTRAL
ROCKIES LATE TODAY INTO FRIDAY THERE IS INCREASING AGREEMENT IN
EVOLUTION OF THE WAVE EVENTUALLY CLOSING OFF IN THE MIDWEST LATE
FRIDAY WITH A DEEPENING SURFACE WAVE THAT SHOWS A STRONG DRY SLOT
AND DEFORMATION ZONE ACROSS THE IA/S MN INTO THE WESTERN GREAT
LAKES...AS WELL A PRESSING THE TRIPLE POINT EASTWARD WITH
SOUTHWARD EXTENDING WELL DEFINED COLD FRONT.  THE 00Z NAM HAS MADE
A DRAMATIC SHIFT SOUTH AND EAST WITH THE SURFACE SOLUTION AND
DEFORMATION ZONE TO LINE UP MORE WITH THE EARLIER FAVORED
ECMWF/GFS/ENSEMBLE MEAN SOLUTIONS.  IT ALSO INDICATES A MUCH
DEEPER SOLUTION INITIALLY...SO MAY BE ADVECTING MOISTURE/FORCING A
BIT FURTHER NORTH THAN THE GFS/ECMWF/ENSEMBLES TO PUT IT WITHIN
THE BLEND BUT AT A MUCH LOWER WEIGHTING.  THE 00Z GFS CONTINUED TO
KEEP IN LINE WITH EARLIER DAY SHIFT SOLUTIONS HAVING SHIFTED FROM
SLOWER AND NORTH OF THE ECMWF TO SLIGHTLY FASTER AND EAST OF THE
12Z ECMWF CURRENTLY.  THE 12Z UKMET CONTINUES TO LAG THE ENSEMBLE
SOLUTIONS LATE DAY 1 INTO DAY 2 ACROSS THE PLAINS INTO THE MIDWEST
BUT ACCELERATES RELATIVE TO THE OTHER GUIDANCE TO BECOME QUITE
AGREEABLE WITH THE ECMWF/GFS/NAM ACROSS THE GREAT LAKES INTO
ONTARIO.   THE 12Z CMC CONTINUES TO TRAIL IN ITS TYPICAL POSITION
AND IS A CLEAR OUTLIER THROUGHOUT THE FORECAST PERIOD.   ALL
CONSIDERED...A BLEND OF THE 00Z NAM/GFS AND 12Z ECMWF SEEMS TO BE
THE DIRECTION OF THE OVERALL CONSENSUS...STILL MODERATE SPREAD
REMAINS ESPECIALLY GIVEN THE TIGHT GRADIENT OF THE DEFORMATION
ZONE/DRY SLOT AND THEREFORE CONFIDENCE IS ABOVE AVERAGE IN THIS
BLEND VERIFYING.  PLEASE REFER TO WPC QPF QPFPFD AND WINTER
WEATHER QPFHSD DISCUSSIONS FOR ADDITIONAL DETAILS.


PAIR OF SHORTWAVES DROPPING ALONG THE WESTERN CANADIAN COAST
TOWARD A MORE AMPLIFIED UPPER LOW OFF THE NORTHWEST COAST BY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/12Z ECMWF
CONFIDENCE: BELOW AVERAGE

CYCLE TO CYCLE ENSEMBLE SPAGHETTI ANALYSIS PLOTS CONTINUE TO SHOW
LARGE VARIATION WITH THE LAST FEW CYCLES DEPENDENT ON HOW MUCH
ENERGY IS SHEARED WEST TOWARD THE DEEP UPPER LOW WELL NORTH OF
HAWAII WITH THE INITIAL WAVE THAT CAN BE SEEN DARKENING IN WV WEST
OF HAIDA GWAII.  THE SUITE SHOWS A TIGHTER PROXIMITY OF THE
WAVES...SO MORE ENERGY IS SHIFTING WEST TO DEEPENING THE DEEP
LOW... WHICH WAS SUGGESTED FIRST BY THE OPERATIONAL ECMWF
YESTERDAY.  THIS ALLOWS THE SECOND WAVE DIGGING OUT OF BC TO HUG
THE US WEST COAST AND TRACK MORE PROGRESSIVELY THROUGH SOUTHERN
CALIFORNIA BY SUNDAY.   THE CURRENT 12Z ENSEMBLE SUITE SHOWS A
LARGE SPREAD IN SOLUTIONS WITH THE CMC/CMCE MEMBERS AND THE UKMET
LAGGING DUE TO BEING A BIT FURTHER WEST AND INTERACTING WITH THE
DEEPER LOW...DRAWING IT EASTWARD TOWARD THE COAST WHILE THE
GFS/GEFS SHOW NEAR ZERO INTERACTION WITH THE DEEP LOW...AND BECOME
VERY PROGRESSIVE INTO THE DESERT SW...EVEN OUTPACING THE 12Z ECMWF
AND 00Z NAM.  THE GFS MORE PROGRESSIVE SOLUTION IS A BIT TOO
AGGRESSIVE (TYPICAL OF A DAY 3 BIAS IN THE GFS) TO SLIGHTLY FAVOR
THE 00Z NAM/12Z ECMWF SOLUTIONS WHICH ARE ON THE WESTERN/SLOWER
SIDE OF THE PROGRESSIVE SOLUTION CAMP.   THE ENSEMBLE MEANS ARE
VERY FLAT GIVEN THE LARGE VARIATION IN MEMBER SOLUTIONS...TO NOT
SUGGEST USING WITHIN A BLEND AT THIS TIME.   STILL THE
TIMING/PLACEMENT OF THE BULK OF MEMBERS WOULD SUPPORT THE
NAM/ECMWF AND THIS WILL BE THE WPC PREFERENCE AT THIS TIME.
GIVEN THE LARGE SPREAD AND LOW PREDICTABILITY OF THE
PATTERN...CONFIDENCE REMAINS BELOW AVERAGE.


NEXT SHORTWAVE DROPPING OUT OF COASTAL BC TO NW WA COAST BY SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/GFS AND 12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE TRAIN OF FAST MOVING BUT STRONG SHORTWAVES CONTINUES TO OVER
TOP THE STRONG ANTICYCLONE DOMINATING THE GULF OF ALASKA.  THIS
BRINGS THE NEXT WAVE INTO THE PACIFIC NORTHWEST AT THE END OF DAY
3...WITH FAIRLY GOOD MODEL CONSENSUS IN TIMING.  THE MAIN SPREAD
CONTINUES TO BE RELATED TO THE DEPTH/STRENGTH OF THE WAVE WITH THE
12Z UKMET MOST AGGRESSIVE WITH DEEPEST/WOUND UP SOLUTION BY 12Z
SUN.  THE 12Z CMC IS UNCHARACTERISTICALLY FAST BUT MUCH MORE
ELONGATED.  THE 00Z GFS SLIGHTLY LESS AMPLIFIED THAN THE 12Z ECMWF
AND 00Z NAM BUT THIS SEEMS MINOR AND A BLEND OF THE 00Z NAM/GFS
AND 12Z ECMWF SEEMS A GOOD COMPROMISE FOR THIS WAVE THROUGH
SUNDAY.  CONFIDENCE IS FAIRLY GOOD FOR DAY 3 IN THIS SOLUTION
SUPPORTED BY FAIRLY GOOD AGREEMENT AND CONTINUITY IN THE ENSEMBLE
SOLUTIONS.


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

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

GALLINA

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