Tropical Storm Oscar Forecast Discussion

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WTNT41 KNHC 210245
TCDAT1

Tropical Storm Oscar Discussion Number   8
NWS National Hurricane Center Miami FL       AL162024
1100 PM EDT Sun Oct 20 2024

Oscar made landfall around 2150 UTC as a 70-kt hurricane near the 
city of Baracoa in the Guantanamo province of eastern Cuba. Radar 
data from Guantanamo Bay shows Oscar has continued to move slowly 
over eastern Cuba tonight, with heavy rainfall spreading across the 
region. Oscar's slow motion will enhance the potential for heavy 
rainfall, life-threatening flash flooding, and mudslides across 
eastern Cuba, particularly near higher terrain. There has been 
notable degradation of Oscar's inner core structure in recent radar 
and satellite images, which suggests weakening is occurring due to 
ongoing land interaction. The initial intensity is lowered to 60 kt 
for this advisory.

Oscar wobbled slightly southward on its final approach to Cuba, but 
recent radar data suggest the system has resumed a slow 
west-southwestward to westward motion. Oscar should remain over 
eastern Cuba or very near the coast during the next 12-24 h. 
Thereafter, the flow ahead of a digging shortwave trough over the 
southwestern Atlantic is forecast to capture Oscar, which should 
result in a northeastward acceleration through midweek. The track 
guidance trended faster this cycle, particularly the ECMWF (which 
has handled Oscar well) and even the GFS with a shallower vortex 
depiction. The NHC track forecast once again shows a faster forward 
speed between 36-72 h, generally between the HCCA/TVCN consensus 
aids and the GFS/ECMWF (GFEX). 

Weakening is expected to continue as the inner core structure of 
Oscar is disrupted by the mountainous terrain of eastern Cuba. The 
extent of the weakening that occurs, and whether Oscar remains a 
tropical cyclone (TC) once it emerges off the northern coast of 
Cuba, is still somewhat uncertain. The ECMWF has been the 
best-performing guidance for Oscar and shows it remaining a TC, 
while other models including the GFS suggest more significant 
weakening and possible degeneration to a surface trough. Even if 
Oscar survives, the environmental conditions over the southwestern 
Atlantic are expected to become more hostile, with stronger vertical 
wind shear and a drier surrounding airmass likely to inhibit much 
redevelopment. The NHC intensity forecast is similar to the previous 
one, but shows post-tropical status at 72 h given the shear. If 
Oscar survives that long, it should become absorbed by a larger, 
non-tropical low pressure system over the western Atlantic by 96 h.

Key Messages:

1. Through midweek, heavy rainfall from Oscar will lead to areas of 
significant, potentially life-threatening flash flooding along with 
mudslides across portions of eastern Cuba, especially within the 
Sierra Maestra. In addition, localized flash flooding will be 
possible across the southeastern Bahamas.

2. Tropical storm conditions are expected to continue overnight 
across portions of eastern Cuba, where a Tropical Storm Warning is 
in effect.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 20.3N  74.6W   60 KT  70 MPH
 12H  21/1200Z 20.4N  75.0W   50 KT  60 MPH...INLAND
 24H  22/0000Z 20.9N  75.3W   40 KT  45 MPH...OVER WATER
 36H  22/1200Z 21.9N  74.9W   40 KT  45 MPH
 48H  23/0000Z 23.4N  73.7W   40 KT  45 MPH
 60H  23/1200Z 25.1N  72.1W   40 KT  45 MPH
 72H  24/0000Z 27.3N  70.2W   35 KT  40 MPH...POST-TROPICAL
 96H  25/0000Z...DISSIPATED

$$
Forecaster Reinhart