889
FXUS10 KWNH 081825
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
224 PM EDT WED JUL 08 2020
VALID JUL 08/1200 UTC THRU JUL 12/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH MODEL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CLOSED LOW MOVING EAST ACROSS SOUTH-CENTRAL CANADA THROUGH FRIDAY
ASSOCIATED COLD FRONT CROSSING THE NORTHERN PLAINS
WEDNESDAY/THURSDAY AND THE GREAT LAKES FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/UKMET/ECMWF BLEND
CONFIDENCE: AVERAGE
19Z UPDATE: THE ECMWF/UKMET CONTINUE TO REMAIN FAIRLY AGREEABLE
AND THE GFS IS A BIT FAST INITIALLY, BECOMING A BIT MORE AMPLIFIED
(LIKELY DUE TO TIMING WITH THE COASTAL LOW) BUT STILL MUCH MORE
TOLERABLE COMPARED TO THE NAM OR 12Z CMC WHICH CONTINUE TO BE TOO
AMPLIFIED. AS SUCH, WILL KEEP WITH INITIAL 12Z GFS/UKMET/ECMWF
BLEND PREFERENCE.
---PRIOR DISCUSSION---
A STRONGER THAN NORMAL, FAIRLY COMPACT SHORTWAVE OVER
SOUTH-CENTRAL CANADA WILL CONTINUE TO LIFT OUT TOWARD NW ONTARIO;
BROAD DIFFLUENCE ON THE NORTHEAST SIDE OF DOMINANT SOUTHWEST RIDGE
WILL SUPPORT AN MCS ACROSS THE NORTH-CENTRAL PLAINS TONIGHT THAT
WILL GROW UPSCALE INTO A SOLID SHORTWAVE THROUGH THE MIDWEST. THE
12Z NAM, POSSIBLY DUE TO HIGHER GRID NETWORK, SHOWS TYPICAL OVER
DEVELOPMENT WITH A VERY STRONG/VERY COMPACT WAVE THAT MAINTAINS
ITSELF THROUGH THE CENTRAL GREAT LAKES FRIDAY EVENING. THIS IS
ENOUGH TO SUGGEST THE NAM IS LIKELY TOO AGGRESSIVE AT THIS POINT,
ESPECIALLY COMPARED TO EARLIER RUNS.
THE 12Z GFS AND 00Z ECMWF CONTINUE TO ANCHOR THE SUITE OTHERWISE,
THOUGH TYPICAL TIMING DIFFERENCES MANIFEST WITH THE GFS FAST AND
ECMWF SLOW. THE 00Z UKMET SEEMS A SOLID MIDDLE GROUND THAT
SUPPORTS BOTH THE CONVECTIVE COMPLEX TRACK/PLACEMENT FEEDING ON
THE LOW LEVEL JET ON THE EDGE OF THE STRONG CAP; BUT ALSO NOT
BUILDING THE RESULTANT UPSCALE SHORTWAVE IN THE MANNER OF THE NAM,
AND EVEN THE 00Z CMC. AS SUCH, WILL FAVOR A 12Z GFS AND 00Z
UKMET/ECMWF BLEND AT AVERAGE CONFIDENCE (GIVEN THE INFLUENCE OF
CONVECTIVE FEATURES TO THE SYNOPTIC EVOLUTION, WHICH IS STILL A
BIT TOO CHAOTIC TO HAVE HIGH CONFIDENCE).
LOW PRESSURE MOVING NORTHEAST ALONG EASTERN SEABOARD INTO THIS
WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/ECENS/GEFS/UKMET/CMC BLEND
CONFIDENCE: AVERAGE TO SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z UKMET SHIFTED NORTH INITIALLY AND PRESENTS A
SIMILAR TIMING TO THE DEVELOPMENT OF THE SURFACE WAVE AS THE
ECMWF/INITIAL PREFERENCE. THE UKMET REMAINS A BIT ON THE STRONGER
SIDE WITH THE WORST CASE SCENARIO, BUT ITS PLACEMENT/TRACK TIMING
LOOK COMPARABLE TO INCLUDE INTO THE PREFERENCE. THE 12Z GEFS
WHILE SHIFTING A BIT WEST OF THE PRIOR GEFS, REMAINS SIMILARLY
TIMED INDICATING THE UNCERTAINTY IN THE FORMATIVE STAGES, BUT
STILL CLOSE TO THE INITIAL PREFERENCE FOR CONTINUED PREFERENCE
OVER THE GFS ITSELF. LIKEWISE, THE CMC IS FAIRLY SIMILAR, BUT
WEAKER THAN THE UKMET. AS SUCH, WILL FAVOR A 12Z
ECMWF/UKMET/CMC/GEFS BLEND AT AVERAGE TO SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
---PRIOR DISCUSSION---
A FAIRLY WEAK SHORTWAVE IS NOTED ALONG THE VA/NC BORDER
PROGRESSING EAST ON GOES-E WV, ALONG WITH THE GULF STREAM
CONVECTION SE OF CAPE FEAR. THE COMBINATION IS EXPECTED TO GROW
UPSCALE AND SUPPORT A WEAK SURFACE WAVE OFF SC TO LIFT NORTH. THE
12Z NAM, POSSIBLY DUE TO THE SMALL GRID SCALE, RAPIDLY DEVELOPS
THE COMPLEX AND CYCLONICALLY ROTATES IT NORTHWARD, EVEN
FASTER/DEEPER THAN THE 00Z SOLUTION. THIS FURTHER ENHANCES INTO
DAY 2 AND DAY 3, WITH THE APPROACH OF THE UPSTREAM OVER-AMPLIFIED
SHORTWAVE ACROSS THE CENTRAL GREAT LAKES/NORTHERN OHIO VALLEY,
WHICH IS ALSO NOT FAVORED. THE GFS CONTINUES A TREND OF LEFT OF
CLUSTER (INCLUDING SIGNIFICANTLY FROM GEFS SOLUTIONS) AS WELL AS
FAST, TYPICAL OF NEGATIVE BIAS KEEPING IT OUT OF THE PREFERENCE.
THE UKMET HAS BEEN STUBBORN ON LIFTING THE MORE VERTICALLY ALIGNED
VORTEX NORTHWARD AND IS DELAYED RELATIVE TO THE OVERALL SUITE.
WHILE, NOT OUT OF THE REALM OF POSSIBILITY AND LIKELY A WORSE-CASE
SCENARIO SUPPORTING STRONGER/DEEPER SURFACE CYCLOGENESIS AS IT
CLIPS SE NEW ENGLAND BY 12.00Z; IT IS NOT FAVORED IN THE BLEND AT
THIS TIME. THIS LEAVES THE CMC AND ECMWF ALONG WITH GEFS/ECENS
MEANS SOLUTIONS; THE CMC SEEMS TO HELP THE NAM/GFS CASE LIFTING
NORTH BUT DOES NOT GO TO THE EXTREME IN CONVECTION/DEPTH OF THE
MID-LEVEL CYCLONE; MUCH MORE SENSIBLE WITHIN THE LONGER TERM
ENSEMBLE SUITE/TREND BUT ALSO CLOSE TO THE GEFS IN TIMING (IF A
TAD LEFT, WHICH IS OK). THE ECMWF/ECENS SHOW GREATEST CONSISTENCY
BUT ALSO A TAD SLOW EVOLUTION, WHICH IS A TYPICAL NEGATIVE
BIAS...SO CANNOT SUPPORT A 100% ECMWF BLEND...BUT TRENDS AND OTHER
SOLUTIONS MAKE IT FAIRLY CLOSE. AS SUCH WILL FAVOR AN ECMWF
DOMINANT BLEND WITH INCLUSION OF THE CMC/GEFS AND ECENS MEANS TO
HELP ACCOUNT FOR UNCERTAINTY. CONFIDENCE REMAINS AVERAGE, GIVEN
THE INFLUENCE OF CONVECTIVE UPSCALE GROWTH/PROXIMITY TO DEEP
LATENT HEAT SOURCE AND UNCERTAINTY OF OUTFLOW/DPVA FROM
APPROACHING SHORTWAVE OUT OF THE OHIO VALLEY.
TROUGH MOVING INTO THE PACIFIC NORTHWEST THURSDAY, OVER-TOPPING
THE RIDGE INTO THE UPPER MIDWEST BY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: WHILE THE CMC CONTINUES TO BE A TAD SOUTH OF THE
FASTER NAM/GFS...IT IS MORE IN LINE WITH THE LATITUDE OF THE
ECMWF, NOW THAT IT HAS PICKED UP PACE. THE ECMWF, LIKE THE CMC,
CONTINUE TO BE ON THE SLOWER AND THEREFORE SOUTHERN SIDE OF THE
GUIDANCE, BUT NOT SUFFICIENTLY TO SUGGEST ANY DEPARTURE. AS SUCH,
WILL FAVOR A GENERAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
---PRIOR DISCUSSION---
A MIDDLE TO LOW AMPLITUDE SHORTWAVE PROGRESSIVELY EXITS THE
PACIFIC NW BY FRIDAY GOING FROM POSITIVE TO NEUTRAL TO SLIGHTLY
NEGATIVE TILT AS IT OVER-TOPS THE CORE OF THE RIDGE IN ID/W MT
INTO SAT. ONLY THE CMC IS GENERALLY SLOW THOUGH THE PLACEMENT OF
THE CORE OF THE SHORTWAVE AS IT TRANSITION THROUGH THE WAVE SHOWS
MODEST SPREAD BEFORE STRETCHING ACROSS THE UPPER MIDWEST BY LATE
DAY SAT. THE UNCERTAINTY WITH CONVECTIVE PLACEMENT IS STILL
RELATED TO THE CAP STRENGTH AND PROGRESSION/PLACEMENT RELATIVE THE
PRECEDING WAVE AND ITS CONVECTIVE ACTIVITY ON THURSDAY THROUGH
FRIDAY. THE ECMWF BEING SLOWER AND LATER, ALLOWS FOR THE CAP TO
PRESS FURTHER SW THAN THE GFS/NAM/UKMET THAT HAD ALREADY EXITED A
FEW HOURS EARLY AND ALLOWED FOR THE LOW LEVEL ENVIRONMENT/CAP TO
REBUILD RELATIVE TO THE ECMWF. THESE ARE TYPICAL BIASES TO
SUGGEST A MIDDLE GROUND BETWEEN THE TWO CAMPS IS PREFERRED. AS
SUCH A NON-CMC BLEND IS PREFERRED, WHICH WILL TILT THE OVERALL
BLEND CLOSER TO THE INCREASED MEMBERS OF THE UKMET/GFS/NAM
RELATIVE TO THE ECMWF WITH RESPECT TO QPF PLACEMENT.
LARGER SCALE TROF DROPPING INTO PACIFIC NW SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
19Z UPDATE: THE ECMWF TRENDED A BIT WEAKER/BROADER WITH THE TROF
OVERALL, BUT HELD WITH THE POSITION OF THE TROF AXIS A BIT FASTER
THAN THE GFS/NAM/UKMET. OVERALL, NO SIGNIFICANT DIFFERENCES IN
THINKING TO CONTINUE A GENERAL MODEL BLEND PREFERENCE THOUGH THE
MODERATE SPREAD KEEPS THE CONFIDENCE AT AVERAGE.
---PRIOR DISCUSSION---
PERHAPS DUE TO THE LATER EXIT OF THE PRECEDING SHORTWAVE, THE
ECMWF/CMC SHOW SHORTER WAVELENGTHS AND SLIGHTLY INCREASED RIDGING
ON SATURDAY, ALLOWING FOR AN EASTWARD/FASTER PROGRESS OF THE
LONGER, HIGHER SCALE TROF COMING THROUGH THE PACIFIC NW ON SAT
INTO SUNDAY. GIVEN THE MOISTURE STREAM IS GENERALLY UPSTREAM OF
THE TROF AXIS, THIS IS A LIMITED AFFECT TO THE PACIFIC NW WITH
RESPECT TO SENSIBLE WEATHER. ADDITIONALLY, LONGER TERM ENSEMBLE
TREND CONTINUE TO MIGRATE TOWARD A CENTRAL COMPROMISE WITH TIME,
AND SUGGEST A GENERAL MODEL BLEND IS AFFORDED BY THE END OF DAY 3
IN THIS REGION. YET, THE REMAINS MODEST SPREAD IN THE TIMING TO
HAVE ONLY AN AVERAGE CONFIDENCE IN THIS BLEND, GIVEN IT IS A BIT
MORE WASHED OUT DUE TO THE MODEST SPREAD ITSELF.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020 WITH THE 21Z ISSUANCE:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
GALLINA
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