794
FXUS10 KWNH 011727
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
126 PM EDT SAT AUG 01 2020
VALID AUG 01/1200 UTC THRU AUG 05/0000 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 TROUGH DIGGING ACROSS THE MID-MS/TN/OH VALLEYS
..SURFACE LOW CROSSING THE OH VALLEY/LOWER GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM/12Z GFS/00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
MID-LEVEL ENERGY IN PLACE OVER THE LOWER OHIO VALLEY SATURDAY
AFTERNOON WILL DRIVE A SURFACE LOW NORTH-NORTHEASTWARD FROM
SOUTHERN IL/IN INTO SOUTHERN ONTARIO/QUEBEC LATE SUNDAY. THE
SHORTWAVE EMBEDDED WITHIN A LONGWAVE TROUGH AXIS WILL LIFT
NORTHEASTWARD INTO CANADA AS WELL BEFORE SHEARING OUT ACROSS
EASTERN CANADA IN SOUTHWESTERLY MID-LEVEL FLOW.
THE 12Z NAM/GFS CONTINUE TO SHOW GOOD AGREEMENT WITH EACH OTHER
AND THE 00Z ECMWF. THE 00Z ECMWF REMAINS A TAD QUICKER WHILE THE
00Z UKMET IS SLOWER. OVERALL, THESE DIFFERENCES ARE RELATIVELY
MINOR BUT QUICKER TRENDS AND THE EVEN SLOWER/WEAKER 00Z CMC STAND
OUT ENOUGH FROM THE GROUP TO DISCOUNT THE 00Z UKMET/CMC. A BLEND
OF THE 12Z NAM/12Z GFS AND 00Z ECMWF LOOK BEST AT THIS TIME
..HURRICANE ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 03Z NHC ADVISORY PACKAGE
BEST MODEL PROXY: NEAR THE 12Z GFS THROUGH 00Z/04
BLEND OF 12Z GFS/00Z CMC 00Z/04 - 00Z/05
THE 15Z NHC FORECAST TRACK OF HURRICANE ISAIAS DOES NOT MATCH ANY
SINGLE MODEL OR MODEL BLEND CONSISTENTLY THROUGHOUT THE 84 HOUR
SHORT RANGE PERIOD. HOWEVER, THE 12Z GFS IS FAIRLY CLOSE TO THE
NHC TRACK, BUT THE GFS IS CLOSER TO THE COAST COMPARED TO NHC
THROUGH TUESDAY. BY MONDAY EVENING, THE 00Z CMC (WHICH WAS WEST OR
SOUTH OF THE NHC TRACK EARLY ON) CATCHES UP AND ACTUALLY OUTPACES
THE NHC TRACK BY A LITTLE WHILE THE 12Z GFS FALLS BEHIND SLIGHTLY
IN TIMING COMPARED TO NHC.
THEREFORE, THE CLOSEST MODEL GUIDANCE TO NHC IS THE 12Z GFS
THROUGH 00Z/04, BUT A BLEND OF THE 12Z GFS AND 00Z CMC FROM 00Z/04
TO 00Z/05. AGAIN, NO SINGLE MODEL OR MODEL BLEND MATCHES EXACTLY
WITH THE NHC TRACK SO CONSULT THE LATEST NHC FORECAST
ADVISORY/DISCUSSION FOR MORE DETAILS.
..NORTHERN STREAM TROUGH SETTING UP OVER THE GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH MONDAY NIGHT
12Z NAM, 12Z GFS AND 00Z ECMWF BLEND TUESDAY
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 LATEST GUIDANCE IS IN FAIR AGREEMENT BUT THE 00Z UKMET/CMC
BECOME A LITTLE WEST OR DEEPER THAN THE REMAINING MODEL CONSENSUS
BY TUESDAY MORNING.
..UPPER LOW/TROUGH APPROACHING THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z CMC BLEND
CONFIDENCE: AVERAGE
TIMING 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 00Z CMC ENDS UP BEING ON THE
WEAKER AND MORE PROGRESSIVE SIDE OF THE GUIDANCE AS THE ENERGY
ADVANCES INLAND. WHILE MINOR TIMING DIFFERENCES REMAIN AMONG THE
NON 00Z CMC GUIDANCE, AGREEMENT IS GOOD ENOUGH TO SUPPORT A
GENERAL MODEL BLEND (EXCLUDING THE 00Z CMC) AT THIS TIME.
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
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