|
Show Selection: |
| #1206380 (Received by flhurricane at: 10:06 PM 03.Nov.2024) TCDAT3 Potential Tropical Cyclone Eighteen Discussion Number 2 NWS National Hurricane Center Miami FL AL182024 1000 PM EST Sun Nov 03 2024 The convective structure of the system in the south-central Caribbean Sea has not become any better organized this evening. Current shower and thunderstorm activity is clustered in two regions to the south and northeast of the estimated center. The center itself remains quite broad and lacks distinct banding features, as seen on an earlier GMI microwave pass at 2219 UTC. Given the lack of improvement from this afternoon, the system remains a Potential Tropical Cyclone (PTC), with an initial intensity at 30 kt. An Air Force Reconnaissance Aircraft is in route to sample the system tonight, and we should soon also receive an ASCAT-B scatterometer pass to provide more information on its structure and intensity. My best guess is that the system continues to move slowly northward this evening, with a current motion a fairly uncertain 360/5 kt. Over the next couple of days, a large mid-level ridge currently parked north of the system off the southeastern U.S. coast should shift a little eastward and build farther southeastward towards Hispaniola. The result of this synoptic pattern should cause PTC18 to turn northwestward and gradually accelerate as it moves into the northwestern Caribbean. This motion should bring the system near Jamaica by Monday evening and the Cayman Islands on Tuesday evening. This northwestward track should continue, likely bringing the system over Cuba and ultimately into the southeastern Gulf of Mexico in 72 h. After that time, the track guidance begins to diverge, with notable ECMWF ensemble cross-track spread in the southwest-to-northeast direction over the Gulf of Mexico. Some of this track spread is related to how fast a mid-latitude cutoff low over the four corners region of the U.S. ejects out into the central Plains. This feature will play a role in how much the mid-level ridging ahead of the system becomes eroded when it emerges into the Gulf of Mexico. The track guidance is a little slower compared to the previous cycle, and the NHC track forecast is also a little bit slower this advisory, while nudged just a hair to the west of the prior forecast at the end of period. However, forecast confidence on the track in the 96-h and 120-h time-frame is lower than usual. The intensity forecast is also uncertain, because how much the system is able to intensify will be determined by its evolving structure over the next couple of days. Environmental conditions in the northwestern Caribbean are forecast to be quite favorable, with SHIPS guidance indicating vertical wind shear remaining 10 kt or lower while traversing very warm 29-30 C sea-surface temperatures for the next 48-60 h. Such an environment could favor rapid intensification, as some of the regional-hurricane model guidance aids were suggesting earlier today. However, this evolution depends on when or if the system is able to develop an inner-core, and the current poor structure argues against substantial development in the short-term. Assuming the system does ultimately develop a better aligned vortex, more significant intensification is forecast in the 24-60 h time frame, and the NHC intensity forecast still shows the system becoming a hurricane in the northwestern Caribbean. After PTC18 crosses Cuba into the Gulf of Mexico, the forecast environment becomes less favorable, with increasing southwesterly shear and decreasing sea-surface temperatures, though this environment is quite dependent on the forecast track. The latest NHC intensity forecast is quite similar to the prior one, splitting the difference between the more aggressive hurricane-regional models, and more subdued global model and statistical-dynamical aids. Key Messages: 1. The disturbance is expected to become a tropical storm Monday and pass near Jamaica on Monday night and Tuesday where a Tropical Storm Warning is in effect. The system is forecast to become a hurricane by Tuesday night and there is a risk of dangerous impacts from hurricane-force winds and storm surge in the Cayman Islands and portions of Cuba. 2. Interests in Cuba and the Florida Keys should closely monitor this system as hurricane and tropical storm watches could be required for portions of these areas on Monday. 3. The system is forecast to enter the western Gulf of Mexico later this week, but given significant uncertainties in the long-range forecast track and intensity, it is too soon to determine what, if any, impacts could occur. Residents in this area should regularly monitor updates to the forecast. 4. The system will bring areas of heavy rain across portions of the western Caribbean, including Jamaica and the southern and western portions of Cuba through mid-week. Flooding could occur over portions of Jamaica and Cuba, with mudslides possible. Heavy rainfall could then spread northward into Florida and adjacent areas of the Southeast United States during the middle to late portions of the week. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 13.3N 76.9W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 04/1200Z 14.2N 76.9W 35 KT 40 MPH...TROPICAL CYCLONE 24H 05/0000Z 16.0N 77.6W 40 KT 45 MPH 36H 05/1200Z 17.9N 78.9W 50 KT 60 MPH 48H 06/0000Z 19.8N 80.9W 60 KT 70 MPH 60H 06/1200Z 21.8N 82.9W 70 KT 80 MPH 72H 07/0000Z 23.5N 84.5W 65 KT 75 MPH 96H 08/0000Z 25.5N 87.0W 65 KT 75 MPH 120H 09/0000Z 26.5N 89.0W 55 KT 65 MPH $$ Forecaster Papin |
