135
FXUS10 KWNH 010441
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1239 AM EDT SAT AUG 01 2020
VALID AUG 01/0000 UTC THRU AUG 04/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..MID-LEVEL TROUGH DIGGING ACROSS THE MID-MS/TN/OH VALLEYS
..SURFACE LOW CROSSING THE OH VALLEY/LOWER GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z NAM/GFS AND 12Z UKMET
CONFIDENCE: SLIGHTLY ABOVE 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 OH VALLEY AND EVENTUALLY THE LOWER GREAT LAKES AND
SOUTHEASTERN CANADA THROUGH SUNDAY NIGHT.
THE 00Z NAM/GFS SOLUTIONS AND THE 12Z NON-NCEP CAMP OF GUIDANCE
ARE MOSTLY IN STRONG AGREEMENT ON THE SYNOPTIC SCALE SET-UP, ALONG
WITH THE DETAILS OF THE EJECTING SHORTWAVE AND ATTENDANT SURFACE
LOW. HOWEVER, THE 12Z CMC GRADUALLY BECOMES A WEAKER OUTLIER WITH
THE SHORTWAVE ENERGY AND SURFACE LOW AND WILL BE DISMISSED.
ADDITIONALLY, FROM ABOUT 36 HOURS ONWARD, THE 12Z ECMWF BEGINS TO
OUTPACE EVERY OTHER PIECE OF GUIDANCE WITH THE FORWARD PROGRESSION
OF THIS SYSTEM. THE 18Z GEFS MEAN AND 12Z ECENS MEAN ARE STRONGLY
SUPPORTIVE OF THE WELL-CLUSTERED 00Z NAM/GFS AND 12Z UKMET
SOLUTIONS, SO A CONSENSUS OF THE LATTER CAMP WILL BE PREFERRED.
..HURRICANE ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 03Z NHC ADVISORY PACKAGE
BEST MODEL PROXY: 00Z GFS
THE 03Z NHC FORECAST TRACK OF HURRICANE ISAIAS IS GENERALLY TO THE
RIGHT OF ALL OF THE NON-NCEP GUIDANCE (I.E. 12Z ECMWF/UKMET/CMC
SOLUTIONS) FROM 24 HOURS ONWARD, AND IS GENERALLY CLOSEST TO 00Z
NAM/GFS BLEND THROUGH 48 HOURS. AFTER 48 HOURS, THE NHC TRACK IS
CLOSEST ULTIMATELY TO THE 00Z GFS, BUT THEN ENDS MUCH BEING
NOTABLY FASTER AS THE 00Z GFS ALONG WITH THE REMAINING MODEL SUITE
HAVE BEEN TRENDING SLOWER WITH THE SYSTEM'S ULTIMATE RECURVATURE
TO THE NORTH AND NORTHEAST AHEAD OF THE UPPER TROUGH MOVING INTO
THE OH/TN VALLEYS. THE 00Z HREF SUITE OF GUIDANCE ON THE OTHER
HAND, MINUS THE NMMB, TAKES ISAIAS TO THE RIGHT OF THE NHC TRACK
THROUGH 48 HOURS. PLEASE CONSULT THE LATEST NHC FORECAST
ADVISORY/DISCUSSION FOR MORE DETAILS.
..NORTHERN STREAM TROUGH SETTING UP OVER THE GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 12Z UKMET/ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
NORTHERN STREAM ENERGY WILL BE DIGGING DOWN ACROSS THE GREAT LAKES
REGION THIS WEEKEND WITH SUGGESTION OF AN ELONGATED CLOSED LOW
DEVELOPING A BIT FARTHER NORTH OVER ONTARIO BY MONDAY AND TUESDAY.
THE 12Z CMC ENDS UP WITH A CLOSED LOW WELL SOUTHWEST OF THE MODEL
CONSENSUS BY TUESDAY AND IS SPATIALLY AN OUTLIER SOLUTION. THE 00Z
GFS AND 12Z UKMET/ECMWF SOLUTIONS ARE VERY WELL CLUSTERED WITH THE
DETAILS OF THE TROUGH/CLOSED LOW AND HAVE STRONG SUPPORT FROM THE
18Z GEFS MEAN AND 12Z ECENS MEAN. THE 00Z NAM FOR ITS PART IS A
TAD SOUTHWEST OF THIS MULTI-MODEL CONSENSUS, BUT NOT TO THE EXTENT
OF THE 12Z CMC. THE MODEL PREFERENCE WILL TOWARD A BLEND OF THE
00Z GFS AND 12Z UKMET/ECMWF CAMP.
..UPPER LOW/TROUGH APPROACHING THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
MODEL DIFFERENCES SHOW UP WITH THE TROUGH AXIS AS IT NEARS BRITISH
COLUMBIA AND THE PACIFIC NORTHWEST LATE ON SUNDAY AND THEN
ADVANCES INLAND ACROSS THE FAR NORTHERN ROCKIES AND ADJACENT AREAS
OF SOUTHWEST CANADA ON MONDAY. THE 12Z CMC ENDS UP BEING A WEAKER
AND MORE PROGRESSIVE OUTLIER WITH THE ENERGY AS IT ADVANCES
INLAND. THE 12Z UKMET AND 12Z ECMWF BOTH GRADUALLY END UP ON THE
SLOWER AND SOMEWHAT DEEPER SIDE OF THE GUIDANCE BY LATE MONDAY AND
TUESDAY AND SUGGEST A CLOSED LOW CENTER CROSSING FAR SOUTHERN
BRITISH COLUMBIA OR NEAR THE BORDER WITH WA STATE AND FAR
NORTHWEST MT. THE 00Z NAM AND 00Z GFS GRADUALLY DO FAVOR A CLOSED
LOW EVOLUTION BUT THEY ARE A LITTLE FARTHER NORTH AND FASTER WITH
THIS FEATURE AND PLACE ANY CLOSED LOW GENERALLY UP ACROSS SOUTHERN
ALBERTA BY THE END OF THE PERIOD. THE 18Z GEFS MEAN AND 12Z ECENS
MEAN ARE MORE SUPPORTIVE OF THE SLOWER UKMET/ECMWF SOLUTIONS, SO
THERE ARE SOME UNCERTAINTIES WITH DEPTH AND TIMING OF THIS ENERGY
TOWARD THE END OF THE PERIOD. FOR NOW, A NON-CMC 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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