Tropical Storm Oscar Forecast Discussion

000
WTNT41 KNHC 191500
TCDAT1

Tropical Storm Oscar Discussion Number   1
NWS National Hurricane Center Miami FL       AL162024
1100 AM EDT Sat Oct 19 2024

Things have been quickly evolving with a small area of low pressure 
located just to the east of the Turks and Caicos Islands. Earlier 
this morning, there was a 0556 UTC AMSR2 passive microwave image 
that suggested the system's structure had become quite a bit better 
organized compared to prior images, with prominent curved bands on 
the 37 GHz low-level channel that suggest a well-defined circulation 
was developing. While the overnight C-band scatterometer imagery 
missed the small circulation just to the west, there was a KU-band 
scatterometer that suggested a closed circulation had formed. First 
light GOES-16 meso-sector imagery also suggests a tight circulation 
has formed, with bubbling hot towers within a small central dense 
overcast taking shape. All these data suggest a tropical cyclone has 
formed, and based on the earlier 12 UTC TAFB T2.5/35 kt Dvorak 
estimate, advisories are being started on Tropical Storm Oscar with 
a 35 kt initial intensity. 

Oscar is estimated to be moving due westward at 270/11 kt. This 
motion should continue for the remainder of the day as the system is 
initially steered by a narrow mid-level ridge positioned to the 
north. However, a digging east-to-west longwave trough is soon 
expected to erode the eastward side of this ridge, causing Oscar to 
slowdown and potentially stall near the northeastern coast of Cuba 
in 36-48 hours. Thereafter, that same trough is expected to continue 
amplifying or even retrograde westward, and if Oscar is vertically 
deep enough, this should induce steering that brings the tropical 
cyclone northeastward. The track forecast lies close to the simple 
TCVA consensus aid, which is quite close to the most recent ECMWF 
forecast. Its worth mentioning, there is quite a bit of 
southwest-to-northeast spread in the ensemble guidance, with weaker 
members slower and further west and stronger members being captured 
by the trough. 

Intensity-wise, Oscar only appears to have a 24 h window for 
strengthening as shear remains low enough.  The first NHC intensity 
forecast shows the system peaking as a 45-kt storm as it nears the 
eastern coast of Cuba.  Shear out of the northwest increases quite 
rapidly after that time, due to the aforementioned trough to its 
north, with the intensity likely leveling off around then. There 
could also be some land interaction with Cuba that could disrupt the 
circulation. However Oscar is a very small tropical cyclone, and 
could be prone to rapid changes in intensity, both up and down. 
After 72 h, the much larger trough is likely to absorb the small 
Oscar, with this occurring by the end of the forecast period by the 
middle of next week.


Key Messages:

1. Oscar is expected to bring tropical storm conditions to portions 
of the southeastern Bahamas, Turks and Caicos Islands, and eastern 
Cuba during the next day or so. A Tropical Storm Warning has been 
issued for those locations.

2. Locally heavy rainfall is possible across the Turks and Caicos 
Islands and the southeastern Bahamas later today and tonight. These 
rains are expected to spread to eastern Cuba on Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 21.3N  70.2W   35 KT  40 MPH
 12H  20/0000Z 21.4N  71.9W   40 KT  45 MPH
 24H  20/1200Z 21.2N  73.8W   45 KT  50 MPH
 36H  21/0000Z 20.9N  74.9W   45 KT  50 MPH
 48H  21/1200Z 21.0N  75.8W   45 KT  50 MPH
 60H  22/0000Z 21.6N  75.9W   45 KT  50 MPH
 72H  22/1200Z 22.5N  75.0W   40 KT  45 MPH
 96H  23/1200Z 25.1N  72.6W   35 KT  40 MPH
120H  24/1200Z...DISSIPATED

$$
Forecaster Papin