566
FXUS10 KWNH 310714
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
313 AM EDT FRI JUL 31 2020
VALID JUL 31/0000 UTC THRU AUG 03/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID-UPPER LEVEL TROUGHING OVER THE OH VALLEY/NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS ALL SHOW REASONABLY GOOD AGREEMENT WITH THE DETAILS OF
THE CURRENT TROUGH OVER THE OH VALLEY AND NORTHEAST THAT WILL BE
GRADUALLY EXITING THE REGION GOING THROUGH SATURDAY. A GENERAL
MODEL BLEND WILL AGAIN BE PREFERRED WITH THIS ENERGY.
..MID-LEVEL TROUGH DIGGING ACROSS THE MID-MS/TN/OH VALLEYS
..NORTHERN STREAM TROUGH DROPPING THOUGH THE GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z NAM/UKMET/ECMWF
CONFIDENCE: AVERAGE
MID-LEVEL ENERGY DIGGING SOUTHEAST ACROSS THE MID-MS VALLEY WILL
DRIVE A TROUGH IN ACROSS MUCH OF THE TN/OH VALLEY GOING THROUGH
THE WEEKEND. THIS WILL BE REINFORCED BY SUNDAY BY AN INTRUSION OF
NORTHERN STREAM TROUGHING DROPPING DOWN ACROSS THE GREAT LAKES
REGION. ON THE SYNOPTIC SCALE, THE MODELS ARE IN GOOD AGREEMENT
WITH TIMING AND DEPTH OF THE HEIGHT FALLS. HOWEVER, THERE ARE SOME
DIFFERENCES WITH RESPECT TO SHORTWAVE ENERGY LIFTING NORTHEAST OUT
OF THE TROUGH ACROSS THE OH VALLEY AND LOWER GREAT LAKES REGION
SUNDAY INTO MONDAY ALONG WITH A WAVE OF SURFACE LOW PRESSURE. THE
00Z GFS IS A TAD STRONGER AND SLOWER WITH THE EVOLUTION OF THIS
ENERGY. THE REMAINING GUIDANCE IS ACTUALLY REASONABLY WELL
CLUSTERED, ALTHOUGH THE 00Z CMC DOES APPEAR TO BE A BIT TOO WEAK
WITH ITS SURFACE LOW EVOLUTION. A BLEND OF OF THE 00Z
NAM/UKMET/ECMWF SOLUTIONS WILL BE PREFERRED WHICH HAVE GOOD
AGREEMENT FROM THE 00Z GEFS MEAN AND YESTERDAY'S 12Z ECENS MEAN.
..HURRICANE ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: SEE NHC SPECIAL 04Z ADVISORY
BEST MODEL PROXY: 00Z GFS/ECMWF BLEND...THROUGH 48 HOURS
00Z GFS/GEFS BLEND...AFTER 48 HOURS
ISAIAS WAS UPGRADED TO A HURRICANE IN A SPECIAL 04Z NHC ADVISORY
PACKAGE. THE 00Z NAM AND YESTERDAY'S 12Z UKMET/ECMWF SOLUTIONS
WERE OVERALL RATHER TIGHTLY CLUSTERED WITH THEIR TRACKS OF ISAIAS
THROUGH 84 HOURS, AND GENERALLY A SOLID 6 TO 12 HOURS SLOWER THAN
THE OFFICIAL NHC FORECAST TRACK BY THE END OF THE PERIOD. HOWEVER,
THE 00Z UKMET HAS SHIFTED ITS TRACK A TAD FARTHER EAST AND IS
NOTABLY STRONGER, WITH THE 00Z ECMWF FARTHER WEST AND GRADUALLY
WEAKER AS THE SYSTEM NEARS THE FL EAST COAST. THEIR TIMING IS
RATHER SIMILAR TO BEFORE BUT THE UKMET AND ECMWF ARE DIVERGENT
WITH THEIR TRENDS. MEANWHILE, THE 00Z CMC JUST LIKE ITS PREVIOUS
RUN IS WEAKER AND THE FARTHEST WEST WITH THE TRACK OF ISAIAS. THE
00Z GFS FOR ITS PART IS AGAIN A PROGRESSIVE OUTLIER AND ENDS UP
NOTABLY FASTER THAN THE NHC TRACK FROM 60 HOURS ONWARD. OVERALL,
THE NHC TRACK IS CLOSE A BLEND OF THE 00Z GFS AND 00Z ECMWF
THROUGH ABOUT 48 HOURS, AND THEN ENDS OF MORE PROGRESSIVE AND
GENERALLY MORE REPRESENTATIVE OF A 00Z GFS/00Z GEFS MEAN BLEND
THEREAFTER WITH PLACEMENT AND FORWARD SPEED.
...COLD FRONT MOVING THROUGH THE NORTH-CENTRAL U.S. FRIDAY AND
SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THIS COLD FRONT IS RELATED TO THE INTRUSION OF NORTHERN STREAM
TROUGHING MENTIONED BEFORE THAT DROPS DOWN ACROSS THE GREAT LAKES
REGION THIS WEEKEND. TIMING DIFFERENCES ARE MODEST WITH THE FRONT,
SO A GENERAL MODEL BLEND WILL BE PREFERRED.
..UPPER LOW/TROUGH APPROACHING THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS BRING A RELATIVELY STRONG UPPER TROUGH FOR THIS TIME OF
THE YEAR INTO THE PACIFIC NORTHWEST BY EARLY MONDAY. THERE ARE
SOME RELATIVELY MODEST DIFFERENCES SEEN WITH SOME OF THE VORT
ENERGY RIDING THROUGH THE BASE OF THIS TROUGH AS THE ENERGY
ARRIVES, BUT THE GUIDANCE IS IN RATHER GOOD AGREEMENT WITH THE
TIMING OF THE HEIGHT FALLS. SO, A GENERAL MODEL BLEND WILL BE
PREFERRED.
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.
ORRISON
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