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| #1108921 (Received by flhurricane at: 4:59 PM 25.Sep.2022) TCDAT4 Tropical Storm Ian Discussion Number 11 NWS National Hurricane Center Miami FL AL092022 500 PM EDT Sun Sep 25 2022 The organization of Ian has not changed much since this morning. There have been some small bursts of convection closer to the center of the storm this afternoon, but the activity has not yet led to any notable changes in its structure. In fact, the most persistent convection has been in outer rainbands well to the northeast of the circulation near Jamaica. The SFMR wind data and adjusted flight-level winds from the earlier reconnaissance flights supported surface winds of 35-40 kt, and the initial intensity is set at 40 kt for this advisory. A NOAA Hurricane Hunter aircraft is scheduled to investigate Ian later tonight. The center of Ian has jogged a bit northward this afternoon, but its longer-term motion is west-northwestward at 300/10 kt. A generally northwestward motion is expected tonight, followed by a north-northwestward motion on Monday and early Tuesday as it moves across the northwestern Caribbean Sea and near or over western Cuba. From there, the track guidance still diverges at days 3-5 as Ian is forecast to move northward across the eastern Gulf of Mexico. The ECMWF and UKMET models still lie on the eastern edge of the guidance and bring the center of Ian over the coast of west-central Florida, while the HWRF and HMON models are on the western side of the envelope and show Ian approaching the central Florida panhandle. Notably, the GFS has trended slightly eastward for the past few cycles, which has brought the multi-model consensus aids a bit eastward as well. The latest NHC track forecast has been adjusted in this direction, but only on the order of 15-20 n mi in the extended range. Users are reminded not to focus on the details of the track forecast at longer time ranges, since uncertainty is still high and future adjustments may be required. Although the storm has yet to develop an inner core, the conditions over the northwestern Caribbean Sea appear very likely to support strengthening once it becomes better organized. Some dry environmental air may have limited convection today, but the GFS- and ECMWF-simulated satellite imagery indicate that deep convection will increase during the diurnal maximum period overnight. Then, significant strengthening is expected with low deep-layer shear and high oceanic heat content along the forecast track. There is still strong support for rapid intensification in the latest intensity guidance, and the NHC intensity forecast shows Ian becoming a hurricane on Monday and a major hurricane on Tuesday. This forecast remains close to the IVCN multi-model consensus, with some model aids including HCCA showing even higher peak intensities. Strong southwesterly shear develops over Ian by 72 h related to interaction with an upper-level trough, and the structure of the cyclone could significantly degrade before landfall given these hostile conditions. However, Ian is likely to have an expanding wind field and will be slowing down by that time, which will have the potential to produce significant wind and storm surge impacts across portions of the Florida west coast and the Florida panhandle. Key Messages: 1. Ian is expected to produce heavy rainfall, flash flooding, and possible mudslides in areas of higher terrain, particularly over Jamaica and Cuba. Flash and urban flooding is possible with rainfall across the Florida Keys and the Florida peninsula through the middle of the week. Additional flooding on rivers across northern Florida and parts of the southeast U.S. cannot be ruled out later this week. 2. Life-threatening storm surge and hurricane-force winds are expected in portions of western Cuba beginning late Monday, and Ian is forecast to be at or near major hurricane strength when it is near western Cuba. Efforts to protect life and property should be rushed to completion. 3. Ian is expected to be a major hurricane in the eastern Gulf of Mexico during the middle of this week, but uncertainty in the track and intensity forecasts remains higher than usual. Regardless of Ian’s exact track and intensity, there is a risk of dangerous storm surge, hurricane-force winds, and heavy rainfall along the west coast of Florida and the Florida Panhandle by the middle of this week, and residents in Florida should ensure they have their hurricane plan in place. Follow any advice given by local officials and closely monitor updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 16.2N 80.3W 40 KT 45 MPH 12H 26/0600Z 17.3N 81.5W 50 KT 60 MPH 24H 26/1800Z 19.2N 82.9W 70 KT 80 MPH 36H 27/0600Z 21.1N 83.7W 90 KT 105 MPH 48H 27/1800Z 23.0N 84.2W 105 KT 120 MPH 60H 28/0600Z 24.8N 84.4W 115 KT 130 MPH 72H 28/1800Z 26.2N 84.4W 110 KT 125 MPH 96H 29/1800Z 28.3N 84.0W 85 KT 100 MPH 120H 30/1800Z 31.0N 83.0W 50 KT 60 MPH...INLAND $$ Forecaster Reinhart |
