657
FXUS10 KWNH 231849
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 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 MODEL EVALUATION INCLUDING FINAL 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 AND EXHIBIT GOOD RUN TO
RUN CONTINUITY.
...MID-UPPER LEVEL TROUGHING TRACKING FROM THE NORTHWEST INTO THE
NORTH-CENTRAL U.S. THROUGH THE WEEKEND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/UKMET 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 12Z UKMET SPED UP FROM ITS 00Z RUN TO MATCH
CLOSER TO THE PREVIOUSLY PREFERRED GFS/ECMWF. THE 12Z CMC TIMING
ALSO LOOKS BETTER WHEN COMPARED TO ITS PREVIOUS 00Z CYCLE, BUT THE
CENTER OF THE CMC UPPER LOW IS DISPLACED NORTH OF THE CONSENSUS.
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/ECMWF/UKMET REPRESENT THE BEST
ENSEMBLE CLUSTERING WHICH LIES IN THE MIDDLE OF THE DETERMINISTIC
SPREAD.
..CALIFORNIA/SOUTHWEST U.S
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z 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 12Z CMC, WHICH IS DISPLACED SLIGHTLY
SOUTH WITH THE LOW-MID LEVEL LOW AND IS WEAKER ALOFT BEGINNING ON
SUNDAY, THE MODELS SHOW VERY GOOD AGREEMENT IN THE SYNOPTIC MASS
FIELDS SUCH THAT A NON 12Z CMC BLEND CAN BE USED FOR THIS SYSTEM.
..TROPICAL DEPRESSION EIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OFFICIAL NHC FORECAST
BEST MODEL PROXY: 12Z ECMWF/UKMET/CMC 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 12Z
ECMWF/UKMET/CMC ARE THE CLOSEST PROXY TO THE 15Z NHC ADVISORY. THE
12Z UKMET REMAINS THE STRONGEST WITH THE 12Z CMC SECOND STRONGEST,
BUT THESE CYCLES MATCH CLOSEST TO THE NHC TRACK. THE 12Z ECMWF
TRACK IS A LITTLE FASTER AND SOUTH OF THE 15Z NHC ADVISORY BUT IS
ALSO A LITTLE WEAKER THAN THE 12Z UKMET/CMC. MEANWHILE, THE 12Z
GFS IS WEAKEST WITH THE LOW-MID LEVEL ORGANIZATION OF THIS SYSTEM
AS IT TRACKS WESTWARD THROUGH THE WESTERN GULF OF MEXICO. THE 12Z
NAM MIGHT BE CONSIDERED AS A SECONDARY PREFERENCE BUT ITS SPEED
WAS NOTED TO BE FASTER THAN THE NHC ADVISORY. 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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