247
FXUS10 KWNH 041648
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 PM EDT TUE AUG 04 2020
VALID AUG 04/1200 UTC THRU AUG 08/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION INCLUDING PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..HURRICANE ISAIAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 15Z NHC ADVISORY PACKAGE
BEST MODEL PROXY: NON-12Z GFS BLEND
THERE WAS GENERALLY GOOD MODEL AGREEMENT WITH THE TRACK OF ISAIAS
AS IT CROSSES EASTERN NY STATE ON ITS WAY INTO QUEBEC BY 05/12Z,
THOUGH THE CONSENSUS WAS A BIT FASTER THAN THE NHC TRACK. THE 12Z
GFS, HOWEVER, WAS MUCH TOO WEAK WITH THE SYSTEM AND CONTINUES THAT
TREND AS IT MOVES INTO EASTERN CANADA THROUGH 05/12Z, AFTER WHICH
TIME THE PRESSURE DIFFERENCES ARE NOT AS EGREGIOUS. DUE TO THE
PRESSURE DIFFERENCE, THE 12Z GFS WAS LEFT OUT OF THE PREFERRED
BLEND. PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY PACKAGE FOR
MORE DETAILS.
..BROAD LONG WAVE TROUGH FROM THE GREAT LAKES TO THE GULF COAST
..CLOSED MID LEVEL LOW OVER ONTARIO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE 12Z GFS BECOMES A BIT FASTER THAN THE TIGHTLY CLUSTERED
CONSENSUS WITH THE BROAD LONG WAVE TROUGH TRACKING ACROSS THE
EASTERN US, WEAKENING AS IT DOES SO. OTHERWISE, THERE IS GENERALLY
GOOD MODEL AGREEMENT AND CONTINUITY WITH THE EVOLUTION OF THE LONG
WAVE TROUGH. THERE IS ALSO GOOD MODEL AGREEMENT (INCLUDING THE 12Z
GFS) WITH THE TRACK OF THE CLOSED MID LEVEL LOW AS IT TIGHTENS AND
CROSSES ONTARIO INTO QUEBEC BEFORE REACHING NEWFOUNDLAND AFTER
08/00Z. BASED ON THE ABOVE, A GENERAL MODEL BLEND IS PREFERRED,
WITH ABOVE AVERAGE CONFIDENCE.
...SHORT WAVE ENERGY DROPPING DOWN OVER THE NORTHERN PLAINS/UPPER
GREAT LAKES WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS TAKING SHORT WAVE
ENERGY FROM SOUTHERN MANITOBA ACROSS THE NORTHERN PLAINS WED,
BEFORE TRACKING IT ACROSS THE UPPER GREAT LAKES BY 06/12Z. AFTER
THAT TIME, THE SHORT WAVE ENERGY BECOMES ABSORBED INTO THE
CIRCULATION OF THE DEEPENING CLOSED LOW MOVING ACROSS QUEBEC AND
NEWFOUNDLAND WED INTO THU. BASED ON THE TIGHTLY CLUSTERED
SOLUTIONS, A GENERAL MODEL BLEND IS PREFERRED WITH THIS.
..SOUTHERN STREAM TROUGH MOVING INTO CA WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS TAKING SHORT WAVE
ENERGY NEAR 29N 129W INTO SOUTHERN CA BEFORE 06/00Z. THERE IS A
SUBTLE HINT OF A CLOSED MID LEVEL CIRCULATION TRYING TO FOR ON THE
NORTHERN PORTION OF THE EVOLVING LONG WAVE TROUGH OVER NORTHERN CA
NEAR 05/12Z, BUT MOST SOLUTIONS KEEP THE TROUGH OPEN. ADDITIONAL
SHORT WAVE ENERGY DROPPING INTO THE BACK SIDE OF THE LONG WAVE
TROUGH THU INTO FRI PULLS THE TROUGH JUST OFFSHORE OF CENTRAL AND
SOUTHERN CA BY 08/00Z. WHILE THERE ARE MINOR DIFFERENCES IN THE
TIMING OF THE SHORT WAVE ENERGY DROPPING INTO THE LONG WAVE TROUGH
POSITION THU/FRI, A GENERAL MODEL BLEND IS PREFERRED WITH ABOVE
AVERAGE FORECAST CONFIDENCE.
...MID LEVEL TROUGH CROSSING THE PACIFIC NORTHWEST WED BEFORE
REACHING ALBERTA/MANITOBA FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS TAKING AN EVOLVING LONG
WAVE TROUGH FROM THE BRITISH COLUMBIA/PACIFIC NORTHWEST COAST THU
MORNING INTO SOUTH CENTRAL ALBERTA BY 07/12Z. AFTER THAT TIME, THE
12Z GFS BECOMES CLOSER THAN THE CONSENSUS, AS IT FORMS A CLOSED
MID LEVEL LOW OVER EAST CENTRAL ALBERTA. THE REMAINDER OF THE
GUIDANCE IS MORE PROGRESSIVE TAKING THE NEGATIVELY TILTED TROUGH
CENTRAL MANITOBA BY THE TIME. THE GFS HAS BEEN SLOWER WITH THIS
FEATURE OVER THE LAST THREE MODEL CYCLES, SO THE 12Z GFS WAS NOT
INCLUDED IN THE PREFERRED BLEND. BECAUSE OF THE CONSISTENTLY
SLOWER GFS, MODEL CONFIDENCE IS SLIGHTLY ABOVE AVERAGE.
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.
HAYES
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