918
FXUS10 KWNH 231708
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
108 PM EDT THU JUL 23 2020
VALID JUL 23/1200 UTC THRU JUL 27/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...BROAD GREAT LAKES/NORTHEAST TROUGH AXIS AND CORRESPONDING COLD
FRONT IMPACTING THE OH VALLEY, NORTHEAST AND MID-ATLANTIC INTO
SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.
...MID-UPPER LEVEL TROUGHING TRACKING FROM THE NORTHWEST INTO THE
NORTH-CENTRAL U.S. THROUGH THE WEEKEND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE
A MID-LEVEL CLOSED LOW/SHORTWAVE TROUGH WILL TRACK THROUGH
SOUTHWESTERN CANADA FRIDAY AND SATURDAY WITH A COLD FRONT LEADING
AT THE SURFACE AND EXTENDING INTO THE NORTHWESTERN U.S. THE MODEL
AGREEMENT IS FAIRLY GOOD THROUGH SATURDAY BUT THE 12Z NAM BEGINS
TO SHOW UP AS FASTEST WITH THE SPEED OF THE MID-LEVEL TROUGH BY
LATE IN THE DAY. THE 00Z UKMET/CMC APPEAR SLOWER THAN THE
CONSENSUS ON SUNDAY. WHILE THE TIMING DIFFERENCES ARE NOT LARGE
AND MODEL-DRIVEN CONVECTIVE BOUNDARY AHEAD OF THE MAIN FRONT COULD
BE MORE SIGNIFICANT. IT SEEMS THE 12Z GFS AND 00Z ECMWF REPRESENT
THE BEST ENSEMBLE CLUSTERING WHICH LIES IN THE MIDDLE OF THE
DETERMINISTIC SPREAD.
..CALIFORNIA/SOUTHWEST U.S
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-00Z CMC BLEND
CONFIDENCE: AVERAGE
AFTER THE DEPARTURE OF A SMALL CLOSED LOW FROM CA TONIGHT, ANOTHER
DISTURBANCE (WEAKER THAN THE FIRST) WILL REACH THE CA COAST LATE
ON SATURDAY. ASIDE FROM THE 00Z CMC, WHICH IS DISPLACED FARTHER
SOUTH AND IS FASTER BEGINNING ON SUNDAY, THE MODELS SHOW VERY GOOD
AGREEMENT IN THE SYNOPTIC MASS FIELDS SUCH THAT A NON 00Z CMC
BLEND CAN BE USED FOR THIS SYSTEM.
..TROPICAL DEPRESSION EIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OFFICIAL NHC FORECAST
BEST MODEL PROXY: 12Z NAM/00Z ECMWF BLEND
CONFIDENCE: REFER TO NHC PRODUCTS
THE 15Z NHC ADVISORY FOR TROPICAL DEPRESSION EIGHT IS IN GENERAL
AGREEMENT WITH THE . THE LATEST MODEL GUIDANCE SHOWS FAIRLY GOOD
AGREEMENT WITH THE LATEST MODEL GUIDANCE. HOWEVER, NONE OF THE
DETERMINISTIC MODELS MATCH EXACTLY WITH THE NHC TRACK FOR ALL OF
THE NEXT 3 DAYS. THERE ARE DIFFERENCES WITH ORGANIZATION OF THE
MID-LEVEL ENERGY ALOFT AS WELL. NHC STRENGTHENS T.D. EIGHT INTO A
WEAK TROPICAL STORM BY FRIDAY MORNING AND MAINTAINS A WEAK
INTENSITY UNTIL LANDFALL WHEN THE SYSTEM WEAKENS BACK BELOW
TROPICAL STORM STATUS.
GIVEN THE TRACK AND INTENSITY FORECASTS BY NHC, A BLEND OF THE 00Z
ECMWF AND 12Z NAM APPEARS TO BE THE CLOSEST PROXY TO THE 15Z NHC
ADVISORY. THE 00Z UKMET IS THE STRONGEST WHILE THE 12Z GFS IS
WEAKEST. THE 00Z CMC IS THE FARTHEST NORTH WITH THE LOW TRACK. FOR
THE LATEST OFFICIAL GUIDANCE, SEE THE MOST RECENT ADVISORY FROM
THE NATIONAL HURRICANE CENTER.
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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