974
FXUS10 KWNH 091841
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
240 PM EDT TUE JUN 09 2020
VALID JUN 09/1200 UTC THRU JUN 13/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z FINAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...TROUGH LIFTING THROUGH THE CENTRAL PLAINS BEFORE ABSORBING INTO
A CLOSED LOW NORTH OF THE GREAT LAKES...
...OCCLUDED LOW AND COLD FRONT MOVING ACROSS THE EASTERN CONUS
THROUGH FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF, 12Z GFS/NAM/UKMET/CMC THROUGH D2
00Z ECMWF, 12Z GFS/UKMET/CMC D3
CONFIDENCE: AVERAGE
19Z UPDATE: THE 12Z NON-NCEP GUIDANCE CAME INTO BETTER AGREEMENT
OVERALL WITH THE NCEP CAMP, EXCEPT THE ECMWF. THE 12Z ECMWF
EVOLUTION OF THE LARGE MID-LEVEL GYRE NORTH OF THE GREAT LAKES
APPEARS TOO FAR WEST WHEN COMPARED TO THE CONSENSUS, AND IS THEN
TOO DRY TO THE EAST. THIS SEEMS UNLIKELY AS THERE IS CONSIDERABLE
MOMENTUM TRANSFER FROM BOTH THE REMNANTS OF CRISTOBAL AND THE
POTENT SHORTWAVE EJECTING FROM THE PLAINS LIFTING INTO THIS GYRE,
WHICH SHOULD PROMOTE A MORE EASTWARD SHIFT OF THE TROUGH AXIS. THE
00Z ECMWF WAS MORE REASONABLE WITH THIS DEVELOPMENT AND REMAINS IN
THE PREFERENCE.
PREVIOUS DISCUSSION:
A CLOSED LOW INITIALLY OVER THE CENTRAL PLAINS WILL EJECT
NORTHEASTWARD AND OPEN AS IT BECOMES ABSORBED INTO A LONGWAVE
TROUGH/CLOSED LOW CENTERED NORTH OF THE GREAT LAKES THURSDAY
MORNING. AN OCCLUDED LOW PRESSURE WILL LIFT NORTHEAST BENEATH
THIS, WITH THE ACCOMPANYING COLD FRONT PUSHING EAST TO BE ALONG OR
JUST OFF THE ATLANTIC COAST FRIDAY MORNING. THE GUIDANCE IS IN
REASONABLY GOOD AGREEMENT WITH THE EVOLUTION OF THESE FEATURES
DESPITE A COMPLEX PATTERN, WITH ONLY THE CMC BEING OUTSIDE THE
ACCEPTABLE ENVELOPE AS IT IS TOO WEAK AND TOO SLOW WITH THE
PROGRESSION OF THE WEAKENING UPPER TROUGH AND SURFACE COLD FRONT.
INTO FRIDAY, THE NAM BECOMES A STRONG OUTLIER WITH THE STRENGTH OF
THE LONGWAVE TROUGH THAT BUILDS IN BEHIND THE COLD FRONT, SO
DESPITE BEING USABLE D1-D2, IT IS REMOVED FROM THE PREFERRED BLEND
BY D3.
..CRISTOBAL REMNANTS
~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE 12Z NCEP AND 12Z NON-NCEP GUIDANCE REMAINS TIGHTLY CLUSTERED
TO THE TRACK AS CRISTOBAL ACCELERATES N/NE INTO CANADA BY
WEDNESDAY NIGHT. ALTHOUGH THE NAM BECOMES SLOWER THAN THE TRACK
AND THE CONSENSUS LATE D2, BY THIS TIME ANY IMPACTS FROM CRISTOBAL
SHOULD BE WELL REMOVED FROM THE CONUS, AND AS SUCH A GENERAL MODEL
BLEND IS SUGGESTED.
...CLOSED LOW OFF BRITISH COLUMBIA AND ASSOCIATED LONGWAVE TROUGH
DIGGING ONSHORE THE WEST COAST THROUGH FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECENS/GEFS
CONFIDENCE: BELOW AVERAGE
19Z UPDATE: THE SPREAD IN THE GUIDANCE INCREASED WITH THE 12Z
NON-NCEP SUITE AS THE ECMWF GOT A BIT FASTER WITH THE SHORTWAVE
MOVING ONSHORE CA D3, WHILE THE UKMET SLOWED DOWN. THERE CONTINUES
TO BE VERY LITTLE RUN-TO-RUN CONSISTENCY OF THE GUIDANCE, AND A
BLEND OF THE MEANS IS PREFERRED AT THIS TIME TO LIMIT SOME OF THE
DIFFERENCES IN THE DETERMINISTIC MODELS.
PREVIOUS DISCUSSION:
CLOSED LOW OFF BRITISH COLUMBIA IS PROGGED TO SPIN NEARLY IN PLACE
THROUGH THURSDAY BEFORE BEGINNING A SLOW JOG SOUTHEAST TOWARDS THE
COAST FRIDAY. SOUTH OF THIS FEATURE, A LONGWAVE TROUGH EXTENDING
FROM THE CLOSED LOW WILL PROGRESS GRADUALLY EASTWARD TOWARDS THE
WEST COAST, WITH AN EMBEDDED SHORTWAVE APPROACHING CA/OR D3. THERE
IS CONSIDERABLE SPREAD, ESPECIALLY BY D3, IN THE PLACEMENT OF THIS
SHORTWAVE, LIKELY DUE TO A WIDE LATITUDINAL SPREAD IN THE POSITION
OF THE CLOSED LOW AT THAT TIME. THE NCEP GUIDANCE IS GENERALLY
FURTHER SOUTH WITH THE CLOSED LOW OFF BC, AND FASTER WITH THE
PROGRESSION OF THE TROUGH INTO CA, WHILE THE NON-NCEP GUIDANCE IS
FURTHER NORTH OFF BC AND THEN SLOWER WITH THE PROGRESSION OF THE
TROUGH. THE GFS HAS BEEN A FAST OUTLIER, AND IS EVEN FASTER AT
12Z, WHILE THE 12Z NAM HAS ALSO SPED UP A BIT FROM ITS PREVIOUS
ITERATION. MEANWHILE THE NON-NCEP GUIDANCE HAS BEEN GRADUALLY
SLOWING, AND SEEMS TO BE MORE TIGHTLY CLUSTERED. AN APPROACH
FAVORING THE 00Z/ECENS SEEMS BEST AT THIS POINT, WITH SOME WEIGHT
INCLUDED OF THE OTHER NON-NCEP MODELS, BUT CONFIDENCE IS BELOW
AVERAGE DUE TO SPREAD AND RUN-TO-RUN INCONSISTENCY.
WEISS
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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