Issued at 1100 AM EDT Sat Oct 19 2024
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
