437
FXUS10 KWNH 281815
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
113 PM EST FRI FEB 28 2020
VALID FEB 28/1200 UTC THRU MAR 03/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES & FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SYSTEM SLOWLY PULLING AWAY FROM THE NORTHEAST THROUGH SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: LITTLE CHANGE, BUT STILL MODEST SPREAD EAST OF THE
CONUS, SUGGESTS THE GENERAL MODEL BLEND OVER THE CONUS WILL
SUFFICE AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
BROAD/ELONGATED CLOSED LOW OVER SW QUEBEC WILL BREAK DOWN A BIT
INTERNALLY AS IT DRIFTS EASTWARD TODAY INTO SUNDAY. PRIOR TO THE
NORTHWEST TO SOUTHEAST ORIENTED UPPER JET/SHEAR AXIS ADVANCES
THROUGH THE NORTHEAST LATER SUNDAY INTO MONDAY, THE INNER CORE
DYNAMICS EVOLVE DIFFERENTLY WITHIN THE NCEP VS NON-NCEP SUITE.
THE GFS/NAM BOTH ARE MORE CENTRAL AND STRONGER WITH THE INNER CORE
SUPPORTING A STRONGER SURFACE OCCLUSION (MAINLY THE 06Z GFS/GEFS)
ROTATING BACK TOWARD MAINE; THIS IS OPPOSED BY THE ECMWF/CMC WHICH
SHOWS A BROADER RING OF ENERGY (VORTEX BREAKDOWN) AROUND A
WEAK/DEVOID CENTROID HUB. THE 12Z GFS TRENDED MORE TOWARD THE
ECMWF EVOLUTION AND FURTHER OFFSHORE WITH THE SURFACE CYCLONE. SO
OVERALL A GENERAL MODEL BLEND COULD BE EMPLOYED AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.
SYSTEM MOVING THROUGH SOUTHERN CANADA & ITS TRAILING FRONT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: SIZABLE SLOWING AND SHIFTS IN THE 12Z UKMET EVOLUTION
MAKE IT MORE IN LINE WITH THE INITIAL PREFERENCE. THE 12Z CMC
SLOWED ALSO MATCHING THE 00Z ECMWF, AND GIVEN THE 00Z ECMWF .
AS SUCH A NON-NAM BLEND IS PREFERRED, AND GIVEN HIGHER CLUSTERING
IN TIMING/EVOLUTION WILL INCREASE CONFIDENCE TO SLIGHTLY ABOVE
AVERAGE
---PRIOR DISCUSSION---
GOES-WEST WV SUITE DEPICTS A COMPACT SHORTWAVE NEARING VANCOUVER
ISLAND AT THIS TIME. THIS WAVE, PARTICULARLY THE LEADING EDGE OF
THE HEIGHT-FALLS AHEAD OF THE UPSTREAM DESCENDING BRANCH OF THE
JET WILL TRACK ACROSS THE SOUTHERN CANADIAN ROCKIES WITH A COMPACT
SURFACE REFLECTION. THE 12Z NAM AND 00Z UKMET ARE A FASTER AND
SHIFTED NORTHEAST WITH GREATER SHEAR AXIS THROUGH CENTRAL
SASK/MANITOBA...LEADING TO GREATER INFLUENCE OF ARCTIC SHORTWAVE
ENERGY (BINARY INTERACTION). WHILE THE NAM, SHOWS A BIT
TIGHTER/COMPACT EVOLUTION THROUGH W ONTARIO, THE UKMET GETS TOO
FAST. THIS IS IMPORTANT GIVEN THE ASSOCIATED FRONTAL ZONE THAT
SLIDES INTO THE NORTHERN TIER AS WELL AS THE DEEP SOUTHWESTERLY
FLOW/SUBTROPICAL TAP OR CONNECTION LATER IN THE FORECAST PERIOD
AHEAD OF THE TWO TRAILING SYSTEMS (SEE SECTIONS BELOW). THE 00Z
ECMWF SHOWS SOME LAGGING COMPACT EVOLUTION THAT RETARDS THE
SURFACE WAVE AND FRONTAL ZONE BY MONDAY RELATIVE TO THE CMC/GFS
AND EVEN THE 00Z ECENS MEAN, MAKING IT A BIT LESS FAVORABLE
OVERALL. AS SUCH WILL SUPPORT SOME OF ITS INCLUSION, BUT MORE
FROM THE 12Z GFS/06Z GEFS AND THE 00Z CMC/ECENS TO HELP PROGRESS
IT A BIT MORE IN TIMING, OF THE FRONT INTO THE GREAT LAKES AS WELL
AS MOISTURE/INSTABILITY FLUX ACROSS THE LOWER MS INTO TN RIVER
VALLEYS BY 84HRS. WHILE THE SPREAD IS FAIRLY SMALL, THE VARIANCE
ALONG WITH STAGING THE ENVIRONMENT IS CRITICALLY IMPORTANT BUT
ALSO IN A LOWER THAN NORMAL PREDICTABILITY FLOW REGIME. STILL,
THE AGREEMENT IS SOLID ENOUGH TO HAVE AVERAGE CONFIDENCE IN THIS
BLEND.
SYSTEM DROPPING DOWN THE WEST COAST SUNDAY & MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND WEIGHTED TOWARD CMC/ECWMF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: FAIRLY CONSISTENT CMC, UKMET AND ECMWF 12Z SOLUTIONS
ALONG WITH SLOWING 12Z GEFS (MATCHING THE GFS) PROVIDES INCREASING
CONFIDENCE TOWARD THE LONGER TERM TREND OF SLOWING/FURTHER SOUTH
DIGGING CLOSED LOW. WHILE THE GFS/GEFS STILL REMAINS WELL EAST OF
THE BEST CLUSTERING, WILL CONTINUES TO KEEP INITIAL PREFERENCE OF
NON-GFS/GEFS BLEND WEIGHTING TOWARD THE CMC/ECMWF.
---PRIOR DISCUSSION---
STRONG SHORTWAVE OFF VANCOUVER ISLAND WILL PRESS EAST, BUT THE
STRONG UPSTREAM ENERGY IN THE UPPER LEVEL JET BEHIND THE MAIN
TROF, WILL ALLOW FOR THE DEVELOPMENT OF AN CLOSED LOW ACROSS N CA
BY MONDAY THROUGH ANTICYCLONIC WAVE BREAK PROCESSES. THIS PROCESS
IS FAIRLY WELL AGREED UPON IN THE SUITE THROUGH 02.00Z (LATE
SUNDAY EVENING), BUT THIS AGREEMENT BEINGS TO FADE AS THE INNER
CORE EVOLVES, AND ITS INTERACTION WITH THE SUBTROPICAL MOISTURE
STREAM AS WELL, AS THE NORTHERN STREAM CONNECTIONS. THE RUN TO
RUN TRENDS IN THE ENSEMBLE SUITE APPEAR TO BE FAVORING A
SLOWING/FURTHER SOUTHWARD DIGGING OF THE CLOSED LOW FIRST
PRESENTED BY THE CMC SUITE, THEN FOLLOWED BY THE ECMWF. THE UKMET
TRENDED THIS WAY, AS WELL AS THE 12Z NAM, PROVIDING INCREASED
CONFIDENCE, AS THE GUIDANCE FALLS INTO THEIR MORE TRADITIONAL BIAS
SPACING RELATIVE TO EACH OTHER. STILL, THE CONNECTION OF THE CMC
TO THE NORTHERN STREAM APPEARS TO BE THE MIDDLE GROUND WITH BEST
CONTINUITY AND WILL CONTINUE TO FAVOR IT AS THE ANCHOR TO THE
PREFERENCE. THE 00Z ECMWF/ECENS MEAN ARE WITHIN TOLERANCE AS
WELL. THE UKMET IS SOLID IN THE SOUTHWEST INTO THE SOUTHERN
PLAINS, BUT THE AFFECTS OF THE STRONGER/FASTER NORTHERN STREAM
(SEE SECTION BELOW) MAKE IT A BIT LESS FAVORABLE, LOWER WEIGHTED
(POSSIBLY HAVING A FASTER STRONGER SUBTROPICAL JET TOO) BUT STILL
INCLUDED. THE 12Z NAM WHILE STILL A BIT NORTH/ELONGATED INTO THE
NORTHERN STREAM RELATIVE TO THE CMC/ECMWF, LOOKS TO MEET AN
ACCEPTABLE EVOLUTION TO HAVE SOME LOWER WEIGHTED INCLUSION AS
WELL. THE 12Z GFS, MUCH LIKE ITS PRIOR RUNS, CONTINUES TO BE
FASTER IN SWINGING THE UPSTREAM SHORTWAVE ENERGY AROUND THE BASE
OF THE DEVELOPING CLOSED LOW, SHIFTING IT EASTWARD, LEADING TO
SUBSTANTIAL MASS DIFFERENCES BY 84HRS IN THE SOUTHWEST. AS SUCH
WILL FAVOR A CMC/ECMWF HEAVY, NON-GFS BLEND AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.
FAST MOVING SHORTWAVE THROUGH BRITISH COLUMBIA, NORTHERN ROCKIES,
POTENTIALLY PHASING WITH SOUTHERN STREAM ACROSS THE CENTRAL PLAINS
INTO TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND (WEIGHT TO ECMWF/CMC/GFS)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: A SLOWING OF THE UKMET BRINGS IT MUCH CLOSER TO THE
TIGHTENING CLUSTER, THOUGH STILL REMAINS THE FASTEST TIMING, BUT
IS SMALL ENOUGH TO HAVE INCLUDED IN THE BLEND. THE CMC WAS A BIT
DEEPER IN AMPLITUDE ACROSS THE HIGH PLAINS, BUT MATCHES THE ECMWF
WELL. ENOUGH TO SUPPORT A GENERAL MODEL BLEND, WITH GREATER
WEIGHTING TOWARD THE ECMWF/CMC/GFS OVER THE UKMET/NAM. AND THOUGH
THE CLUSTERING IS TIGHT CURRENTLY, THE PLACEMENT TO THE TERRAIN
AND TRACK STILL SUGGEST THERE IS POTENTIAL FOR A DIFFERENT
EVOLUTION COMING TO FRUITION, SO CONFIDENCE IS ONLY INCREASED TO
SLIGHTLY ABOVE AVERAGE.
---PRIOR DISCUSSION---
A VERY IMPORTANT SHORTWAVE TO THE EVENTUAL HIGH HAZARD/FLOODING
CONCERN IN THE MEDIUM-RANGE ACROSS THE MS VALLEY INTO THE TN
VALLEY WILL HAVE SOME IMPACT TO THE VERY END OF THE SHORT-TERM
FORECAST PERIOD ACROSS THE PACIFIC NW AND NORTHERN HIGH PLAINS.
THIS WAVE IS STILL WELL NORTH ALONG THE ALEUTIAN CHAIN AND IS
EXPECTED TO TRACK ALONG THE ALASKAN PENINSULA, BEFORE OVER-TOPPING
THE BROAD GULF OF AK RIDGE AND DROPPING THROUGH THE CENTRAL
CANADIAN ROCKIES BY 12Z MONDAY. VORTICAL STRETCHING AND SHARP
250MB LEFT EXIT, ANTICYCLONIC CURVATURE WILL SUPPORT COMPACT SPIN
UP OF THE WAVE AND SUPPORT SURFACE CYCLOGENESIS THROUGH N ALBERTA
TO SASKATCHEWAN, BUT STILL BROAD ASCENT AS FAR SOUTH AS THE
CENTRAL US ROCKIES BY 03.00Z. THIS IS FAIRLY LOW PREDICTABILITY
TRACK FOR PRECISE DEPTH/STRENGTH THOUGH THERE IS INCREASINGLY
TIGHTENING IN THE GUIDANCE SUITE. THE IMPORTANCE OF THE PLACEMENT
IS CRITICAL TO THE PLACEMENT/TIMING OF PHASING WITH THE SOUTHWEST
SYSTEM LIFTING OUT, AFTER 84HRS. THE 00Z CMC/ECMWF/ECENS MEAN
HAVE BEEN CONSISTENT PROVIDING THE CENTROID OF INITIAL PREFERENCE.
THIS WILL LEAD THE FASTER UKMET (TYPICAL OF BIAS) A BIT OUT OF
TOLERANCE. THE 12Z NAM IS A BIT SLOWER AND FURTHER NORTH, WHICH
MAY HAVE SOME MORE TO DO WITH THE RESOLUTION OF THE TERRAIN AND
THE VORTICAL SPIN UP, SHOWING THE UNCERTAINTY/LOW PREDICTABILITY
ENVIRONMENT. THE 12Z GFS, HOWEVER, SAW SIZABLE ADJUSTMENT TOWARD
THE TREND AND LOOKS TO BE A GOOD MATCH AT LEAST FOR THIS SYSTEM
AND THROUGH 84HRS. THIS WAS DUE TO A SLIGHT ADJUSTMENT NORTH,
SLOWING AND INJECTING LESS ENERGY FROM THIS WAVE TOWARD
PULLING/KICKING THE SOUTHWEST WAVE OUT INTO THE PLAINS. SO WILL
PREFER A 00Z CMC/ECMWF AND 12Z GFS BLEND BUT CONFIDENCE WILL BE
AVERAGE GIVEN THE RUN TO RUN VARIANCE EXPECTED IN THIS FLOW
REGIME/CYCLONE TRACK.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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