000 WTNT43 KNHC 051449 TCDAT3 Tropical Storm Rafael Discussion Number 8 NWS National Hurricane Center Miami FL AL182024 1000 AM EST Tue Nov 05 2024 Satellite imagery shows that the convection has increased near the center of Rafael during the past several hours. However, reports from an Air Force Reserve Hurricane Hunter aircraft suggest that this has not yet translated into strengthening, possibly due to what looks like a tongue of dry air seen entraining into the center in microwave imagery. The aircraft reported maximum winds of 54 kt at 850 mb with a minimum central pressure near 994 mb. Based on the aircraft data, the initial intensity remains 50 kt. One note is the radius of maximum winds has decreased to about 20 n mi, suggesting that Rafael is trying to develop a better-defined inner core despite the apparent dry air. The initial motion is still northwestward at 320/11 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 couple of days, with the center passing near the Cayman Islands and over western Cuba. After that time, there is a significant spread in the track guidance. While all of the guidance suggests that Rafael should shear apart over the central and northern Gulf, the GFS takes longer to show this happening than the ECMWF/UKMET. In addition, the GFS shows a weaker ridge north of the system, while the ECMWF/UKMET show a stronger ridge. The result is that the GFS shows a northward motion with landfall on the northern Gulf coast, while the ECMWF/UKMET show a westerly motion across the central Gulf of Mexico. Until there is a clearer signal on which of these scenarios is more likely, the forecast compromises between these extremes with a slow motion over the northern Gulf of Mexico. Conditions are favorable for steady to rapid strengthening during the next 24-36 h if Rafael can develop a stronger inner wind core. Based on the expectation that the core will form, the system is forecast to reach hurricane strength in about 12 h and continue to strengthen until it reaches Cuba. Once the center is north of 25N in the Gulf of Mexico, it 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. The new intensity forecast remains on the high side of the intensity guidance and is similar to the previous forecast. Key Messages: 1. Rafael is forecast to be near hurricane intensity when it passes near or over the Cayman Islands by tonight where damaging hurricane-force winds, a dangerous storm surge, and destructive waves are expected. Rafael should reach western Cuba and the Isle of Youth on Wednesday. A hurricane warning is in effect for this region, where a life-threatening storm surge and destructive waves are also expected. 2. Tropical storm conditions are expected in Jamaica through this afternoon. 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 the islands of Jamaica and the Cayman, 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 05/1500Z 17.8N 78.6W 50 KT 60 MPH 12H 06/0000Z 19.4N 79.9W 65 KT 75 MPH 24H 06/1200Z 21.3N 81.5W 75 KT 85 MPH 36H 07/0000Z 23.2N 83.1W 80 KT 90 MPH 48H 07/1200Z 24.4N 84.3W 80 KT 90 MPH 60H 08/0000Z 25.1N 85.7W 80 KT 90 MPH 72H 08/1200Z 25.6N 87.1W 75 KT 85 MPH 96H 09/1200Z 26.8N 89.3W 60 KT 70 MPH 120H 10/1200Z 28.0N 90.5W 45 KT 50 MPH $$ Forecaster Beven