Issued at 400 PM EST Tue Nov 05 2024
000 WTNT43 KNHC 052041 TCDAT3 Tropical Storm Rafael Discussion Number 9 NWS National Hurricane Center Miami FL AL182024 400 PM EST Tue Nov 05 2024 Reports from an Air Force Reserve Hurricane Hunter aircraft and radar data from Grand Cayman indicate that Rafael has developed an inner wind core during the past several hours. The radar data shows the development of a ragged eye, and the Hurricane Hunter reported 850-mb flight-level winds of 73 kt about 30-35 n mi northeast of the center. The aircraft also reported that the central pressure has fallen to near 989 mb. Based on these data, the initial intensity is increased to 60 kt. The wind radii have been revised some based on the aircraft data. The initial motion is northwestward at 325/13 kt. Rafael is currently on the southwestern side of a low- to mid-level ridge over the western Atlantic, and this feature should steer the cyclone generally northwestward for the next 36-48 h, with the center passing near the Cayman Islands and over western Cuba. From 48-72 h, the models are in better agreement that the center should turn more westward as the ridge builds a little westward along the northern Gulf coast. After 72 h, there remains some significant spread in the track guidance, due partly to differences in how fast Rafael will shear apart and due partly to differences in the forecast strength of the ridge along the Gulf coast. The GFS weakens the ridge and shows a northward turn, while the ECMWF keeps a stronger ridge and shows a more westward motion. The deterministic UKMET has now changed to a northward turn scenario, but the HWRF, HMON, and UKMET ensemble mean join the ECMWF with a westward motion. As mentioned with the previous forecast, until there is a clearer signal on which of these scenarios is more likely, the forecast compromises between these extremes with a slow turn toward the north over the northern Gulf of Mexico. Now that Rafael has developed an inner wind core, conditions are favorable for steady to rapid strengthening during the next 24 h or so. The system is expected to reach hurricane strength during the next several hours as it passes through the Cayman Islands with additional strengthening before it reaches Cuba. While the peak intensity forecast is near the high end of the intensity guidance, there is a chance that Rafael could get stronger than currently forecast. Once the center is north of 25N in the Gulf of Mexico, the cyclone is likely to encounter increasing vertical wind shear, dry air entrainment, and cooler sea surface temperatures, which should lead to Rafael weakening and eventually shearing apart vertically. This part of the intensity forecast lies near or just above the intensity consensus. Key Messages: 1. Rafael is forecast to be a hurricane when it passes near or over the Cayman Islands during the next 12 hours, where damaging hurricane-force winds, a dangerous storm surge, and destructive waves are expected. Additional strengthening is expected before Rafael reaches western Cuba and the Isle of Youth on Wednesday. A hurricane warning is in effect for this region, where damaging hurricane-force winds, life-threatening storm surge, and destructive waves are also expected. 2. Tropical storm conditions are expected in the Lower and Middle Florida Keys beginning Wednesday and Wednesday night. 3. It is too soon to determine what, if any, impacts Rafael could bring to portions of the northern Gulf Coast. Residents in this area should regularly monitor updates to the forecast. 4. Rafael will bring areas of heavy rain across portions of the western Caribbean through early Thursday, including Jamaica and the Cayman Islands, along with southern and western portions of Cuba. Flash flooding and mudslides are possible along the higher terrain in Jamaica and Cuba. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 19.1N 79.6W 60 KT 70 MPH 12H 06/0600Z 20.5N 80.7W 70 KT 80 MPH 24H 06/1800Z 22.5N 82.4W 80 KT 90 MPH 36H 07/0600Z 24.1N 83.8W 80 KT 90 MPH 48H 07/1800Z 25.0N 85.2W 80 KT 90 MPH 60H 08/0600Z 25.4N 86.5W 75 KT 85 MPH 72H 08/1800Z 25.8N 87.8W 65 KT 75 MPH 96H 09/1800Z 27.1N 90.1W 50 KT 60 MPH 120H 10/1800Z 28.8N 90.7W 40 KT 45 MPH $$ Forecaster Beven