005
FXUS10 KWNH 120639
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 AM EDT FRI JUN 12 2020
VALID JUN 12/0000 UTC THRU JUN 15/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..TROUGH AMPLIFYING ACROSS THE EAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: THE ECMWF/CMC BOTH TRENDED A BIT STRONGER INITIALLY
WITH THE WAVE EMERGING FROM THE GREAT LAKES, WHILE THE NAM/GFS
CONTINUE TO BE THE STRONGER/SYMMETRIC, THE UKMET/CMC BOTH ARE LESS
CONCENTRATED BUT STILL GENERALLY LOCATED IN THE SAME AREA. THIS
LEADS TO BETTER QPF CLUSTERING BUT STILL GIVEN THE MESOSCALE
NATURE IT REMAINS HARD TO LOCK DOWN ESPECIALLY BY DAY 3...BUT IT
IS ENOUGH TO INCREASE CONFIDENCE TO SLIGHTLY ABOVE AVERAGE
---PRIOR DISCUSSION---
A THE START OF THE FORECAST PERIOD, A FAIRLY DRY AVERAGE LONG-WAVE
TROF SITS ACROSS ONTARIO/QUEBEC WITH THE MOISTURE STREAM/FRONTAL
ZONE DISPLACED ALONG THE COASTAL CAROLINAS. AS THE TROF MATURES
AND THE CORE MOVES OFF TOWARD THE LABRADOR SEA, THE POSITIVE TILT
BASE WILL SWING THROUGH THE NORTHEAST UNDER LITTLE FANFARE/MODEL
DIFFERENCE. UPSTREAM JET ENERGY/SHORTWAVE WILL DIG THROUGH THE
GREAT LAKES ON SAT INTO THE UPPER OHIO VALLEY/CENTRAL
APPALACHIANS, EVENTUALLY BUILDING TO THE GREATER MODEL
UNCERTAINTY; ALIGNED WITH TYPICAL MODEL BIASES. THE 00Z GFS/NAM
AND LESSER SO, 12Z UKMET ARE FASTER TOWARD EVOLUTION AND A MORE
COMPACT/SYMMETRIC CLOSED LOW BY LATE SUNDAY, WHILE THE SLOWER TO
EVOLVE ECMWF/CMC ARE FLATTER AND PROGRESS SOUTHEAST OF THE HIGHER
TERRAIN TOWARD THE LINGERING FRONTAL ZONE/MOISTURE AXIS THROUGH
THE PIEDMONT REGION OF THE CAROLINAS/VIRGINIA. THE LATTER, BEING
WEAKER BUT CLOSER TO THE MOISTURE, PRODUCE CONVECTION A BUT EAST
RELATIVE TO THE STRONGER BUT MORE DISTANT DRAWING OF THE GFS/NAM.
A COMPROMISE BETWEEN THE CAMPS IS PREFERRED AS BOTH SEEM
ESTABLISHED IN THEIR INHERENT BIASES. CONFIDENCE IS AVERAGE GIVEN
NO ONE SOLUTION PROVIDES THE IDEAL PLACEMENT OF THE
FORCING/INSTABILITY AND MOISTURE ELEMENTS AND A BLEND OF ALL THE
MODELS WILL SMEAR THE SENSIBLE WEATHER ELEMENTS.
...LONGWAVE TROUGH OFF THE WEST COAST AND SHORTWAVE LIFTING
ONSHORE CALIFORNIA BY THE WEEKEND...
..CLOSED LOW DEVELOPING ACROSS THE NORTHERN ROCKIES SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/ECWMF/UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: THE ECWMF/UKMET CONTINUE TO PROGRESS SIMILARLY TO
PRIOR RUNS AND MATCH THE NAM GENERALLY. THE 00Z CMC TRENDED
SLOWER WITH THE LEAD WAVE, AND THEREFORE DEPICTS A TIGHTER BINARY
INTERACTION WITH THE INNER CORE OF THE CLOSED LOW AS IT CUTS
ACROSS THE NORTHERN ROCKIES INTO SW CANADA. THIS LEADS THE
AMPLIFICATION TO BE GREATER AND DISPLACE THE BINARY NORTH AND WEST
RELATIVE TO THE REST OF THE SUITE (AS THE GFS INNER CORE TRENDS
BETTER TOO. AS SUCH A 00Z NAM/ECMWF AND UKMET BLEND WILL BE
PREFERRED THOUGH SOME INCORPORATION OF THE CMC WITH THE LEAD WAVE
IS TOLERABLE, MUCH LIKE SOME INCLUSION OF THE GFS IS OK WITH THE
INNER CORE WAVE BY DAY 3 IN THE NORTHERN ROCKIES. CONFIDENCE
REMAINS SLIGHTLY ABOVE AVERAGE.
---PRIOR DISCUSSION---
GOES-W WV SUITE DEPICTS A CLOSED LOW TO THE NW OF VANCOUVER ISLAND
PRESSING EAST WITH A SHORTWAVE FEATURE LENGTHENING THE LONG-WAVE
TROF SOUTHWARD AS IT APPROACHES THE SW/OR/N CA COAST. THE
SHORTWAVE WILL MOVE FULL-BODILY INTO N CA TOMORROW, WITH THE
CLOSED LOW DRIFTING EAST. THE MODELS ARE IN GOOD AGREEMENT IN THE
EVOLUTION AND TIMING OF THE CLOSED LOW, BUT THE 00Z GFS CONTINUES
TO SNAP THE BASE SHORTWAVE NORTHWARD THROUGH THE US ROCKIES INTO
THE S CANADIAN ROCKIES MUCH TO FAST. THIS LEADS THE DEVELOPING
SURFACE WAVE TO BE TUCKED TIGHT TO THE TERRAIN AND WELL WEST OF
THE BEST OVERALL ENSEMBLE CLUSTER, INCLUDING THE BULK OF THE GEFS
MEMBERS. THE FASTER EVOLUTION ALSO ALLOWS FOR THE WAVE TO BE
FAVORABLY LOCATED IN THE UPPER LEVEL JET PATTERN, TO FURTHER
DEEPEN/STRENGTH RELATIVE TO THE OTHER GUIDANCE.
EVENTUALLY, THE INNER CORE OF THE UPPER-LOW WILL SWING THROUGH THE
PACIFIC NORTHWEST UNDER THE PRECEDING SHORTWAVE, EVEN THOUGH THE
GFS IS NOT SOLID WITH THE PRECEDING WAVE, THE CORE IS STILL OK AS
IT SWINGS NEGATIVE TILT THROUGH THE NORTHERN HIGH PLAINS EARLY
MONDAY, PROVIDING CONFIDENCE IN THE OVERALL PROGRESSION. AS SUCH
A NON-GFS BLEND IS PREFERRED AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
...APPROACHING CLOSED LOW TO THE PACIFIC NORTHWEST BY EARLY
MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~
PREFERENCE: 00Z NAM/ECMWF/CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: THE 00Z ECMWF TRENDED A BIT WEST/FASTER TOWARD
AMPLIFICATION OF THE WAVE, BUT STILL RELATIVELY CLOSE TO THE 00Z
NAM. THE CMC REDUCED THE MOISTURE PLUME/FLUX INTO THE WEST COAST;
AND WHILE STILL A BIT EAST OF THE NAM IN THE MASS FIELDS, APPEARS
A BIT MORE TOLERABLE OVERALL IN THE SUITE TO SUPPORT A 00Z
NAM/CMC/ECMWF BLEND AT SLIGHTLY ABOVE AVERAGE GIVEN THE UKMET IS
TRENDING EASTWARD TOO.
---PRIOR DISCUSSION---
ON THE HEELS OF THE BINARY INTERACTION ACROSS THE PACIFIC
NORTHWEST/NORTHERN ROCKIES IN THE LATE WEEKEND, ANOTHER SHORTWAVE
WILL PROGRESS ALONG THE ALEUTIAN CHAIN INTO THE GULF OF AK BY
SUNDAY. THE 00Z GFS AND 12Z UKMET ARE IN TYPICAL FASTER POSITIONS
WITHIN THE GUIDANCE SUITE, WHICH EVENTUALLY LEADS TO EARLIER AND
THEREFORE FURTHER WEST POSITIONING OF THE WAVE AS IT BECOMES A
CLOSED LOW LATE SUNDAY INTO MONDAY. THE NAM/ECWMF AND CMC ALL
PRESS EASTWARD AND SLOWER TO OCCLUDE, LEADING TO THE MODEL SPREAD.
OVERALL, IT IS NOT LARGE (WITH EXCEPTION TO THE PLACEMENT OF THE
SURFACE LOW), BUT THE ONSHORE FLOW/MOISTURE FLUX IS FAIRLY
AGREEABLE WITH THE EXCEPTION OF THE CMC WHICH IS
UNCHARACTERISTICALLY WET ACROSS THE WEST COAST BY THE END OF THE
SHORT-TERM FORECAST PERIOD (84HRS). THINK THE TIMING ISSUES FAVOR
THE THE SLOWER EVOLUTION, SO WILL FAVOR A 12Z ECMWF/00Z NAM BLEND
THOUGH SOME INCORPORATION OF THE GFS/UKMET SEEMS PLAUSIBLE TO
ACCOUNT FOR SOME OF THE REMAINING UNCERTAINTY, BUT GENERALLY
AVOIDED THE CMC IN QPF. CONFIDENCE IS AVERAGE IN THIS BLEND
GALLINA
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