890
FXUS10 KWNH 301904
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
304 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 MODEL EVALUATION INCLUDING FINAL 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. NO SIGNIFICANT CHANGES
WERE NOTED IN THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS
00Z CYCLES, OTHER THAN A SLIGHT NUDGE FASTER WITH THE EXITING
TROUGH AXIS.
...MID-LEVEL ENERGY ADVANCING SOUTH FROM THE PLAINS TODAY TO THE
LOWER MS VALLEY FRI AND OHIO VALLEY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 12Z NAM/GFS/UKMET
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/ECMWF FASTEST AND
12Z UKMET SLOWEST. WHILE THE 12Z CMC REMAINS WEAKER/FLATTER WITH
THE TROUGH AXIS, THE 12Z ECMWF/UKMET TRENDED QUICKER. THE MODELS,
ESPECIALLY THE UKMET, HAVE BEEN FLIP FLOPPING BACK AND FORTH
BETWEEN SLOWER/STRONGER (00Z) AND QUICKER/SLIGHTLY WEAKER (12Z)
CYCLES. THE PREFERENCE IS TO BE NEAR THE MIDDLE OF THE PAST FEW
CYCLES OF DETERMINISTIC/ENSEMBLE GUIDANCE, OR NEAR THE 12Z
NAM/GFS/UKMET WHICH IS A SLIGHT NUDGE FASTER THAN THE PREVIOUS
PREFERENCE. THE 12Z ECMWF MAY HAVE UTILITY EARLIER IN THE
FORECAST, BUT THE 12Z CMC APPEARS TO HAVE THE LOWEST LIKELIHOOD OF
VERIFYING.
..TROPICAL STORM ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CLOSEST PROXY TO 15Z NHC ADVISORY...
THROUGH 12Z/02: 12Z ECMWF
12Z/02 - 00Z/03: 12Z NAM/12Z GFS BLEND
CONFIDENCE: REFER TO NHC PRODUCTS
THE MODELS HAVE SIGNIFICANT DIFFERENCES ON THE TRACK AND SPEED OF
TROPICAL STORM ISAIAS FOR THE WEEKEND, WITH THE 12Z
ECMWF/UKMET/CMC GENERALLY SOUTH AND WEST OR SLOWER THAN THE 15Z
NHC ADVISORY. MEANWHILE THE 12Z GFS IS FASTER, NORTH AND EAST OF
THE 15Z NHC ADVISORY. THE CMC HAS BEEN CONSISTENTLY DISPLACED
SOUTH AND/OR SLOW WITH THE TRACK OF ISAIAS COMPARED TO NHC FOR
SEVERAL CYCLES.
THROUGH SATURDAY NIGHT, BEFORE MODEL DIFFERENCES EXPAND, THE 12Z
ECMWF IS FAIRLY CLOSE TO THE 15Z ADVISORY FOR THE TRACK OF ISAIAS.
A BLEND OF A BLEND OF THE 12Z NAM AND 12Z GFS ALSO GETS FAIRLY
CLOSE TO THE NHC TRACK. BY SUNDAY EVENING HOWEVER, THE 12Z ECMWF
SLOWS RELATIVE TO THE NHC ADVISORY WITH A 50/50 BLEND OF THE 12Z
NAM/GFS LOOKING REASONABLY CLOSE TO THE FORECAST NHC POSITION. THE
12Z UKMET IS ALSO FAIRLY CLOSE TO THE NHC TRACK BUT BECOMES
INCREASINGLY SLOWER THROUGH SATURDAY AND SUNDAY. 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: SLIGHTLY ABOVE 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. NO SIGNIFICANT CHANGES WERE NOTED IN THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES.
..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. NO
SIGNIFICANT CHANGES WERE NOTED IN THE 12Z ECMWF/UKMET/CMC COMPARED
TO THEIR PREVIOUS 00Z CYCLES.
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.
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