138
FXUS10 KWNH 290706
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
305 AM EDT THU AUG 29 2019
VALID AUG 29/0000 UTC THRU SEP 01/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-00Z NAM BLEND LED BY THE 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..07Z UPDATE
SPREAD REMAINS IN THE LATEST GUIDANCE ACROSS THE CENTRAL U.S. WITH
THE 00Z NAM CONTINUING TO STAND OUT THE GREATEST (SEE BELOW).
ADJUSTMENTS BY THE 00Z UKMET/CMC APPEAR TO BE POSITIVE ALTHOUGH
THE 00Z UKMET REMAINS FLAT WITH THE 500 MB TROUGH ACROSS THE OHIO
VALLEY. A NON 00Z NAM BLEND OF GUIDANCE WITH HEAVY WEIGHTING
TOWARD THE 00Z ECMWF IS PREFERRED ACROSS THE CENTRAL U.S., WHILE A
GENERAL MODEL BLEND CAN CONTINUE TO BE USED ELSEWHERE ACROSS THE
LOWER 48.
..PREVIOUS DISCUSSION FOLLOWS
THE SOUTHERN END OF LONGWAVE TROUGHING OVER THE GREAT LAKES/OHIO
VALLEY AT THE START OF THE PERIOD IS FORECAST TO LIFT
NORTHEASTWARD THROUGH SATURDAY WHILE LOWER AMPLITUDE LONGWAVE
TROUGHING REDEVELOPS JUST EAST OF THE MISSISSIPPI RIVER SUNDAY
MORNING. MEANWHILE, MID-UPPER LEVEL RIDGING OVER CA/AZ WILL
TRANSLATE TOWARD THE FOUR CORNERS REGION THROUGH SUNDAY MORNING AS
A SHORTWAVE NEARS THE PACIFIC NORTHWEST SUNDAY MORNING.
SOME OF THE GREATEST DIFFERENCES ACROSS THE CONUS ARE ACROSS THE
CENTRAL U.S. ARE WITH THE WESTERN END OF A FRONTAL BOUNDARY ACROSS
THE CENTRAL PLAINS. A MCS IS FORECAST TO DEVELOP OVER EASTERN
NEBRASKA/KANSAS LATE THURSDAY NIGHT WHICH HAS IMPLICATIONS ON THE
LATITUDE OF THE EFFECTIVE FRONT INTO FRIDAY NIGHT AND SATURDAY.
THE 00Z NAM IS THE MOST AGGRESSIVE WITH THE BOUNDARY SINKING WELL
SOUTH INTO THE SOUTHERN PLAINS. THE 12Z ECMWF APPEARS TO BE THE
MOST REASONABLE REGARDING RUN TO RUN CONTINUITY AND AGREEMENT WITH
THE LATEST ENSEMBLE MEANS. AT 500 MB, THE 12Z UKMET/00Z GFS APPEAR
TO BE FLATTER/FASTER (RESPECTIVELY) WITH THE CORRESPONDING TROUGH
AXIS SATURDAY MORNING. THE 12Z UKMET APPEARS TO HAVE CONVECTIVE
FEEDBACK WHILE THE 12Z CMC IS AN OUTLIER WITH ITS NORTHERN SURFACE
WAVE POSITION THROUGH SUNDAY MORNING.
ELSEWHERE ACROSS THE CONUS, A GENERAL MODEL BLEND IS PREFERRED
GIVEN GOOD AGREEMENT.
..TROPICAL DEPRESSION ERIN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/UKMET/CMC CLOSEST TO 03Z NHC ADVISORY
CONFIDENCE: REFER TO NHC
..07Z UPDATE
THE 00Z ECMWF ADJUSTED TOWARD THE WEAKER 00Z GFS REGARDING THE
SURFACE LOW OF WHAT IS CURRENTLY TROPICAL DEPRESSION ERIN.
MEANWHILE, WESTWARD SHIFTS IN THE 00Z UKMET/CMC MAKE THESE MODELS
CLOSE ENOUGH TO THE 03Z NHC ADVISORY TO ALLOW INCLUSION AS PART OF
A BLEND, EXCLUDING THE 00Z GFS/ECMWF.
..PREVIOUS DISCUSSION FOLLOWS
THE 00Z GFS IS A BIT OF AN OUTLIER WITH THE STRENGTH OF ERIN
THROUGH FRIDAY DEPICTING A WEAKER SYSTEM RELATIVE TO THE REMAINING
DETERMINISTIC GUIDANCE. THE 12Z UKMET/CMC ARE DISPLACED EAST OF
THE 03Z ADVISORY NHC TRACK WHILE THE 12Z ECMWF/00Z NAM ARE CLOSEST
TO NHC.
..HURRICANE DORIAN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 00Z GFS/ECMWF/CMC CLOSEST TO 03Z NHC ADVISORY
CONFIDENCE: REFER TO NHC
..07Z UPDATE
SHIFTS IN THE 00Z UKMET/CMC WERE SLOWER COMPARED TO THEIR PREVIOUS
CYCLES WHILE THE 00Z ECMWF ONLY MADE MINOR ADJUSTMENTS. A BLEND OF
THE 00Z ECMWF/CMC/GFS PLACES A POSITION NEAREST TO THE 03Z NHC
ADVISORY TRACK FOR HURRICANE DORIAN.
..PREVIOUS DISCUSSION FOLLOWS
THE 00Z GFS, 12Z ECMWF AND 12Z UKMET ARE CLOSEST TO THE 03Z NHC
ADVISORY TRACK REGARDING HURRICANE DORIAN THROUGH ABOUT SATURDAY
MORNING. AFTER THIS POINT IN TIME, THE 00Z GFS DEVIATES NORTH AND
WEST OF THE NHC FORECAST POSITIONS BUT THE 12Z ECMWF/UKMET REMAIN
CLOSE TO THE NHC TRACK. THE 12Z CMC IS A FASTER OUTLIER WITH
DORIAN WHILE THE 00Z NAM IS SLOWER WITH THE TRACK.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
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