352
FXUS10 KWNH 120432
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1231 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: AVERAGE
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: NON-GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
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/12Z ECMWF BLEND
CONFIDENCE: AVERAGE
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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