Hurricane Isaac Discussion Number  15
NWS National Hurricane Center Miami FL       AL102024
300 PM GMT Sun Sep 29 2024

Hurricane Isaac continues to maintain a small inner-core, which has 
proved resilient in an increasingly unfavorable environment  
characterized by strong deep-layer vertical wind shear near 30 kt 
and sea surface temperatures (SSTs) around 23C. The satellite 
appearance of the hurricane has been relatively steady this morning, 
with consistent bursts of deep convection near the center. The 
initial intensity is set to a possibly generous 65 kt, which is on 
the higher end of the subjective and objective intensity estimates.

The tropical cyclone is forecast to track over cooler SSTs and into 
increasing west-southwesterly vertical wind shear, which will induce 
steady weakening through the forecast period. The intensity forecast 
is similar to the previous forecast. There is evidence on visible 
satellite this morning that Isaac has begun to interact with a 
baroclinic zone to its north and east, in addition to wrapping dry 
air from the northwest around the southern side of the circulation. 
These factors are likely to result in Isaac becoming an 
extratropical cyclone by Monday.

Isaac's forward motion continues to be northeastward (045/10 kt) as 
it is steered by deep-layer southwesterly flow. This general motion 
should continue for the next day or so, with a turn toward the 
north-northeast expected by the middle part of this week in response 
to a mid- to upper-level trough approaching from the west. The 
cyclone is then forecast to turn back towards the northeast beyond 
72 hr as it tracks along the southeastern periphery of an 
upper-level trough. Once again, the track forecast is adjusted 
eastward from the previous advisory beyond the 24 hr period, in 
agreement with the latest consensus guidance. 


FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 43.2N  35.6W   65 KT  75 MPH
12H  30/0000Z 44.0N  33.6W   55 KT  65 MPH
24H  30/1200Z 45.1N  30.3W   50 KT  60 MPH...POST-TROP/EXTRATROP
36H  01/0000Z 46.6N  26.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
48H  01/1200Z 48.5N  25.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
60H  02/0000Z 50.6N  24.3W   35 KT  40 MPH...POST-TROP/EXTRATROP
72H  02/1200Z 52.8N  23.1W   35 KT  40 MPH...POST-TROP/EXTRATROP
96H  03/1200Z 57.1N  18.6W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  04/1200Z 61.2N  14.2W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Mahoney/Papin