Tropical Storm Ileana Forecast Discussion

000
WTPZ44 KNHC 150237
TCDEP4

Tropical Storm Ileana Discussion Number  11
NWS National Hurricane Center Miami FL       EP092024
800 PM MST Sat Sep 14 2024

Ileana has stalled near the coast of northwestern Mexico, offshore
of the state of Sinaloa.  All of the deep convection has moved
inland, as indicated by both the radar and satellite imagery,
leaving the low-level circulation exposed.  Surface observations
from Topolobampo and Los Mochis recently measured sustained winds of
39 kt, with higher gusts.  Based on these data, the initial
intensity for this cycle is raised to 40 kt.

The storm is drifting with an uncertain motion of 360/1 kt.  Ileana
is still expected to turn northwestward soon and gradually
accelerate, bringing the center across the northern coastal region
of Sinaloa during the next 12 h.  By Sunday, the cyclone is forecast
to be near the coast of southern Sonora and stay roughly parallel to
the coast of Mexico over the Gulf of California until the system
dissipates. The new track forecast is again nudged to the north and
east of the previous track and lies near the various consensus
models.

Despite strong southwesterly vertical wind shear decoupling
Ileana's surface circulation from its deep convection, the surface
winds have yet to weaken.  Global models indicated that deep
organized convection should not reform and therefore Ileana is
expected to become a post-tropical cyclone by Sunday.  The system
should gradually weaken due to the interaction with land and
surrounding dry air and strong vertical wind shear.  The official
forecast shows Ileana dissipating by late Monday, though some
numerical guidance suggests this could occur sooner.


Key Messages:

1. Tropical Storm Ileana will bring heavy rainfall to portions of
coastal Sinaloa, Mexico through this weekend. This heavy rainfall
will bring a risk of flash flooding and mudslides to portions of the
area.

2. Tropical storm conditions are expected within the warning area
of northern Sinaloa and southern Sonora through Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 25.5N 109.0W   40 KT  45 MPH
 12H  15/1200Z 25.7N 109.2W   35 KT  40 MPH...POST-TROPICAL
 24H  16/0000Z 26.4N 109.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  16/1200Z 27.4N 110.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  17/0000Z...DISSIPATED

$$
Forecaster Bucci