Hurricane Isaac Discussion Number  11
NWS National Hurricane Center Miami FL       AL102024
300 PM GMT Sat Sep 28 2024

Isaac's strengthening trend from the past day or so appears to have
leveled off. Isaac still has a clear eye and a relatively symmetric
appearance, although some dry air entrainment is evident coming in
from the southwest. Intensity estimates range from 77 to 93 kt, and
initial intensity has been held at 90 kt, in agreement with TAFB's
Dvorak classification of 5.0. The wind radii have been modified to 
reflect values from 1245 UTC ASCAT-B pass.

Isaac is already over relatively cool water and will reach 
progressively lower SSTs in the coming day or two, all while 
encountering increasingly hostile shear. Thus, Isaac's intensity has 
most likely peaked, and gradual weakening today is forecast to 
accelerate through the weekend. This weakening will coincide with an 
extratropical transition, which based on global models, will 
complete in about 48 hours. The NHC intensity forecast remains 
unchanged from the previous forecast and is in close agreement with 
consensus aids through the forecast period.

Isaac is moving east-northeastward, 060/17 kt. Steering flow
should decrease as Isaac passes in the vicinity of a mid- to upper-
level ridge over the next day or so, which should lead to slower
forward motion through the remainder of its warm-core existence.  As
Isaac becomes extratropical, it should turn more northerly as a
shortwave trough digs to the west of the cyclone. The official track
forecast remains unchanged through 48 hours but has again trended to
the right of the previous forecast beyond 48 hours to adjust closer
to consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 40.2N  39.7W   90 KT 105 MPH
12H  29/0000Z 41.4N  37.8W   85 KT 100 MPH
24H  29/1200Z 42.9N  36.1W   75 KT  85 MPH
36H  30/0000Z 44.0N  33.9W   65 KT  75 MPH
48H  30/1200Z 45.4N  31.5W   55 KT  65 MPH...POST-TROPICAL
60H  01/0000Z 47.1N  29.4W   45 KT  50 MPH...POST-TROPICAL
72H  01/1200Z 49.6N  28.7W   45 KT  50 MPH...POST-TROP/EXTRATROP
96H  02/1200Z 53.5N  28.1W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  03/1200Z 56.6N  25.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Konarik/Cangialosi