960
FXUS10 KWNH 301711
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
111 PM EDT THU JUL 30 2020
VALID JUL 30/1200 UTC THRU AUG 03/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID-UPPER LEVEL TROUGHING OVER THE NORTHEAST TO THE OHIO VALLEY
AND MID ATLANTIC THROUGH SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.
...MID-LEVEL ENERGY ADVANCING SOUTH FROM THE PLAINS TODAY TO THE
LOWER MS VALLEY FRI AND OHIO VALLEY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF
CONFIDENCE: AVERAGE
MID-LEVEL ENERGY EMANATING FROM THE CENTRAL PLAINS WILL ADVANCE
THROUGH THE OZARKS TONIGHT BEFORE AMPLIFYING INTO LARGER SCALE
TROUGHING ALONG THE MS RIVER VALLEY BY SATURDAY/SUNDAY MORNING.
ASSOCIATED WITH THE UPPER TROUGH, THE MODELS DEVELOP SURFACE LOW
PRESSURE IN THE LOWER MS RIVER VALLEY FRI NIGHT TO EARLY SAT
BEFORE THE LOW ADVANCES TOWARD THE OH VALLEY.
THERE REMAIN TIMING DIFFERENCES WITH THE 12Z NAM/12Z GFS FASTEST,
ALTHOUGH THE 12Z NAM IS FASTEST. THE 00Z UKMET TRENDED BACK TOWARD
A SLOWER/STRONGER SOLUTION ALOFT WITH THE UKMET FLIP FLOPPING BACK
AND FORTH BETWEEN ITS 00Z (SLOWER/STRONGER) AND 12Z
(QUICKER/SLIGHTLY WEAKER) CYCLES. MEANWHILE, THE 00Z CMC IS WEAKER
WITH THE TROUGH OVERALL, BUT NOT AS FAST AS THE 12Z NAM. THE 00Z
ECMWF IS SLOWER THAN THE 12Z GFS BUT SLIGHTLY FASTER THAN ITS
ENSEMBLE MEAN, WITH A MIDDLE GROUND FAVORED. THE CLOSEST BLEND FOR
A MIDDLE OF THE ROAD APPROACH IS BETWEEN THE 12Z GFS AND 00Z ECMWF.
..TROPICAL STORM ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CLOSEST PROXY TO 15Z NHC ADVISORY...
THROUGH 12Z/01: 12Z NAM, 12Z GFS, 00Z ECMWF BLEND
12Z/01 - 00Z/03: 12Z NAM/12Z GFS BLEND
CONFIDENCE: REFER TO NHC PRODUCTS
THE MODELS HAVE SIGNIFICANT DIFFERENCES ON THE TRACK OF TROPICAL
STORM ISAIAS, WITH THE 00Z ECMWF/UKMET/CMC GENERALLY SOUTH AND
WEST OF THE 15Z NHC ADVISORY. MEANWHILE THE 12Z GFS IS NORTH AND
EAST OF THE 15Z NHC ADVISORY. THE 00Z UKMET/CMC ARE CONSISTENTLY
DISPLACED SOUTH AND/OR SLOW WITH THE TRACK OF ISAIAS COMPARED TO
NHC.
THROUGH SATURDAY MORNING, BEFORE MODEL DIFFERENCES EXPAND, A BLEND
OF THE 12Z NAM, 12Z GFS AND 00Z ECMWF IS CLOSEST TO THE NHC TRACK.
FROM SATURDAY MORNING THROUGH SUNDAY EVENING, A 50/50 BLEND OF THE
12Z NAM AND 12Z GFS POSITIONS IS CLOSEST TO THE NHC TRACK. IT
SHOULD BE NOTED THAT THE 12Z GFS SHOWS A STRONGER SYSTEM WHEN
COMPARED TO THE NHC ADVISORY AND REMAINING DETERMINISTIC GUIDANCE
BY SUNDAY AFTERNOON.
...COLD FRONT MOVING THROUGH THE NORTH-CENTRAL U.S. FRIDAY AND
SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THERE IS RELATIVELY GOOD AGREEMENT FOR THE TROUGH AXIS AND RELATED
COLD FRONT IMPACTING THE NORTH-CENTRAL U.S. THROUGH SATURDAY.
WHILE MINOR TIMING DIFFERENCES ARE EVIDENT, A GENERAL MODEL BLEND
APPEARS REASONABLE GIVEN THE DIFFERENCES ARE SMALL ENOUGH AT THIS
TIME.
..UPPER LOW/TROUGH APPROACHING THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
FAIRLY GOOD AGREEMENT CONTINUES IN THE MODELS FOR THIS SYSTEM WITH
ONLY MINOR TIMING DIFFERENCES NOTED. RUN TO RUN CONSISTENCY HAS
BEEN GOOD AND ENSEMBLE SPREAD IS RELATIVELY SMALL. THEREFORE
CONFIDENCE IS SLIGHTLY HIGHER THAN AVERAGE FOR THIS SYSTEM.
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:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
OTTO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page