301
FXUS10 KWNH 311903
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 PM EDT FRI JUL 31 2020
VALID JUL 31/1200 UTC THRU AUG 04/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION, INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..MID-LEVEL TROUGH DIGGING ACROSS THE MID-MS/TN/OH VALLEYS
...SURFACE LOW TRACKING THROUGH THE OH VALLEY ON SATURDAY AND INTO
SOUTHEASTERN CANADA SUNDAY NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL NON-NAM MODEL BLEND.
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 BUT A LEAD SHORTWAVE WITHIN THE INITIAL TROUGHING WILL
COINCIDE WITH A SURFACE LOW TRACKING ACROSS THE MS RIVER VALLEY
INTO THE MIDWEST AND EVENTUALLY SOUTHEASTERN CANADA FOR SUNDAY
NIGHT.
THE 12Z NAM IS STRONGER WITH UPPER LEVEL JET ENERGY IN THE BASE OF
THE TROUGH AXIS NEAR THE GULF COAST SUNDAY MORNING WHICH LEADS TO
A STRONGER AND SOUTHEASTWARD DISPLACED TROUGH AXIS ON ITS
SOUTHEASTERN SIDE BY SUNDAY EVENING. MEANWHILE WITH THE NORTHWARD
TRACKING SURFACE LOW INTO CANADA, THERE ARE ONLY MINOR
DIFFERENCES, BUT THE 00Z ECMWF WAS A LITTLE FASTER THAN THE
CONSENSUS LATE SUNDAY. OVERALL, A CONSENSUS OF THE NON-NAM 12Z
GUIDANCE IS REASONABLE HERE.
..HURRICANE ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: SEE 15Z NHC ADVISORY
BEST MODEL PROXY: 12Z GFS
WHILE NOT AN EXACT MATCH TO NHC, THE 12Z GFS APPEARS REASONABLY
CLOSE TO NHC THROUGH 00Z/04, HOWEVER THIS SOLUTION IS MORE INLAND
THAN THE NHC TRACK BY ABOUT 30-50 MILES. OTHERWISE, THE 12Z ECMWF
WAS NOTABLY FARTHER WEST WITH THE TRACK OF ISAIAS, SIMILAR TO (BUT
A LITTLE FASTER THAN) THE 12Z UKMET, UP THROUGH CENTRAL FL AND
EVENTUALLY OFF THE NORTHEAST FL COAST BY MONDAY EVENING. THE 12Z
CMC/CANADIAN MEANWHILE IS THE FARTHEST LEFT/WEST WITH THE TRACK,
BASICALLY UP THE WEST COAST OF FL. THERE IS A NEED FOR INCREASING
WEIGHT ON THE 12Z GFS'S FASTER SPEED FOR 12Z/03 AND 00Z/04, NOTING
BOTH THE NAM AND GFS ARE FARTHER WEST OF THE NHC TRACK BY ABOUT
30-50 MILES (WHILE THE NAM IS SLOWER THAN THE GFS, YET FASTER THAN
THE ECMWF, UKMET, AND CMC).
...NORTHERN STREAM TROUGH SETTING UP OVER THE WESTERN GREAT LAKES
REGION BY MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
DIFFERENCES WITH THE PHASING OF, OR LACK THEREOF, MID-LEVEL ENERGY
TRACKING THROUGH MANITOBA AND ONTARIO AFFECT THE PATTERN EVOLUTION
OVER THE WESTERN GREAT LAKES REGION AND MIDWEST FOR EARLY NEXT
WEEK. ENSEMBLE MEANS SUPPORT A 12Z GFS/00Z ECMWF BLEND WITH THE
12Z NAM AND 00Z CMC INDICATING LESS PHASING TO THE NORTH AND
GREATER AMPLIFICATION OF TROUGHING NEAR LAKE SUPERIOR AND DOWN
INTO THE MS VALLEY ON MONDAY. THE 00Z UKMET IS PLAUSIBLE AS
ANOTHER OPTION SIMILAR TO THE 12Z GFS AND 00Z ECMWF.
..UPPER LOW/TROUGH APPROACHING THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/CMC BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
TIMING DIFFERENCES SHOW UP WITH THE TROUGH AXIS AS IT NEARS
BRITISH COLUMBIA AND THE PACIFIC NORTHWEST LATE ON SUNDAY. THE 12Z
NAM AND 00Z UKMET ARE MORE NOTED TO BE MORE PROGRESSIVE WITH A
SHORTWAVE IN THE BASE OF THE TROUGH ON MONDAY. THE PATTERN FROM
THE NORTHEASTERN PACIFIC INTO THE SOUTHERN HALF OF CANADA IS
RATHER AMPLIFIED AND MAY FAVOR SLOWER PROGRESSION. THIS IS
REPRESENTED IN THE AGREEABLE ENSEMBLE MEANS WITH A SLOWER TROUGH
AXIS THAN EVEN THE 12Z GFS/ECMWF/CMC THROUGH MONDAY NIGHT. THE
PREFERENCE IS TO GO WITH THE SLOWER SIDE OF THE DETERMINISTIC
SPREAD AT THIS POINT, NOTING THAT ENSEMBLE SPAGHETTI PLOTS SHOW A
GREAT DEAL OF SPREAD WITH NO DEFINED TRENDS.
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/HURLEY
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page