965
FXUS10 KWNH 021728
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
127 PM EDT SUN AUG 02 2020
VALID AUG 02/1200 UTC THRU AUG 06/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID-LEVEL SHORTWAVE LIFTING FROM THE LOWER GREAT LAKES INTO
SOUTHEASTERN CANADA THROUGH TONIGHT WITH ACCOMPANYING SURFACE
LOW...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.
..TROPICAL STORM ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 03Z NHC ADVISORY PACKAGE
BEST MODEL PROXY: THROUGH 12Z/04: 12Z GFS, 00Z ECMWF, 00Z CMC BLEND
00Z/05 - 12Z/05: 00Z ECMWF/UKMET/CMC BLEND
00Z/06: NEAR THE 00Z ECMWF
THE 15Z NHC FORECAST TRACK OF TROPICAL STORM ISAIAS IS OVERALL
CLOSEST NOW TO A MULTI-MODEL BLEND CONSISTING OF THE 12Z GFS, 00Z
ECMWF, 00Z UKMET AND 00Z CMC. THE MODEL'S PROXIMITY TO NHC VARIES
OVER THE COURSE OF THE NEXT 3 DAYS, BUT THE 12Z NAM STANDS OUT THE
GREATEST WITH A TIMING THAT IS 6 TO 12 HOURS SLOWER THAN THE NHC
TRACK THROUGH WEDNESDAY MORNING. INDIVIDUAL MODEL TIMING VARIES
CONSIDERABLY COMPARED TO THE NHC TRACK, WHERE SOME MODELS THAT ARE
INITIALLY SLOWER THAN NHC (00Z UKMET), SPEED UP THEIR TIMING TO BE
FASTER THAN NHC BY WEDNESDAY AFTERNOON. HOWEVER, ALL OF THE MODELS
SUPPORT THE SYSTEM RAPIDLY LIFTING THROUGH NEW ENGLAND BY THE END
OF THE PERIOD. PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY
PACKAGE FOR MORE DETAILS.
...NORTHERN STREAM TROUGH SETTING UP OVER THE GREAT LAKES ON
MONDAY/TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 06Z GEFS/00Z ECENS BLEND, OR NEAREST TO THE 12Z NAM,
12Z GFS AND 00Z UKMET
CONFIDENCE: AVERAGE
NORTHERN STREAM ENERGY WILL BE DIGGING DOWN ACROSS THE GREAT LAKES
THROUGH SUNDAY WITH LIKELY DEVELOPMENT OF AN ELONGATED CLOSED LOW
A BIT FARTHER NORTH OVER ONTARIO BY MONDAY AND TUESDAY. THE 00Z
ECMWF/UKMET AND 00Z CMC DIFFER WITH THE HANDLING OF TWO MAIN
VORTICITY MAXIMA WITHIN THE LARGER SCALE TROUGH. THE 00Z ECMWF
STANDS OUT THE GREATEST FROM THE DETERMINISTIC/ENSEMBLE GUIDANCE
BUT THERE IS GROWING SUPPORT FOR A SOLUTION EDGING IN THE
DIRECTION OF THE 00Z ECMWF NOTED BY ITS MEAN AND THE 00Z
UKMET/CMC. HOWEVER, A BLENDED APPROACH NEAR THE 12Z NAM, 12Z GFS
AND 00Z UKMET IS NEAREST TO THE PREFERENCE OF THE ENSEMBLE MEANS
AT THIS POINT, WITH THE ENSEMBLE MEANS CONSIDERED BEST.
..UPPER LOW/TROUGH CROSSING THE PACIFIC NORTHWEST TONIGHT
...ENERGY DROPPING DOWN OVER THE NORTHERN PLAINS/MIDWEST FOR
TUESDAY/WEDNESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM, 12Z GFS, 00Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE
AN UPPER TROUGH WILL CROSS IN THROUGH BRITISH COLUMBIA AND THE
PACIFIC NORTHWEST TONIGHT AND THEN TRACK WELL INLAND THROUGH
MONDAY AND TUESDAY WITH THE MAIN FOCUS OF THE HEIGHT FALLS
REMAINING ACROSS WESTERN AND CENTRAL CANADA. HOWEVER, THE GUIDANCE
SUPPORTS SOME ENERGY IN THE BASE OF THE TROUGH SEPARATING OUT
ACROSS THE FAR NORTHERN ROCKIES AND THEN ADVANCING SOUTHEAST BY
WEDNESDAY ACROSS THE NORTHERN PLAINS AND MIDWEST. THE 12Z NAM/GFS
REMAIN ON THE STRONGER SIDE OF THE GUIDANCE WITH THIS ENERGY OVER
THE NORTHERN U.S. MONDAY NIGHT THROUGH TUESDAY...AS IS THE 00Z
CMC. THIS IS REFLECTED IN THE LATEST ENSEMBLE SPAGHETTI PLOTS
WHICH INDICATE THE NAM/GFS/CMC ON THE EDGES OF THE LATEST MEMBER
DISTRIBUTION. HOWEVER, THE 00Z ECMWF/UKMET ARE WEAKER AND FASTER
WITH THIS SYSTEM TRACKING NEAR THE U.S./CANADIAN BORDER. THE 00Z
UKMET AND 00Z CMC ARE ON THE EDGES OF THE LATEST DETERMINISTIC
GUIDANCE, AND SO THE PREFERENCE IS TO EQUALLY WEIGHT THE 12Z NAM,
12Z GFS AND 00Z ECMWF. THE THINKING HERE IS THAT A BLENDED
APPROACH OF THESE MODELS WILL BE CLOSEST TO VERIFICATION, LYING IN
THE MIDDLE OF THE MODEL SPREAD AND NEAR THE MIDDLE GROUND
CONSIDERING TRENDS.
..SOUTHERN STREAM TROUGH MOVING INTO CA BY WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARY WITH THIS SYSTEM.
...MID-UPPER LEVEL TROUGH NEARING THE PACIFIC NORTHWEST LATE
WEDNESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
ONLY MINOR TIMING DIFFERENCES WERE NOTED, BUT AGREEMENT IS FAIRLY
GOOD FOR A DAY 3 FORECAST.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page