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| #1108885 (Received by flhurricane at: 10:59 AM 25.Sep.2022) TCDAT4 Tropical Storm Ian Discussion Number 10 NWS National Hurricane Center Miami FL AL092022 1100 AM EDT Sun Sep 25 2022 The satellite presentation of Ian is gradually improving this morning. The overall circulation appears better defined in visible satellite imagery, and fragmented bands of convection around the center are showing increased signs of curvature. The low-level center of Ian also appears better defined in the latest data collected by the NOAA and Air Force Hurricane Hunters. Although the vortex is still vertically tilted, tail Doppler radar data suggest the low- and mid-level centers are beginning to converge. An earlier center dropsonde indicated the minimum pressure dropped slightly to 1001 mb, but the aircraft winds thus far have not reflected any strengthening. Therefore, initial intensity for this advisory is held at 45 kt. The latest fixes suggest Ian is beginning to make its turn around the western side of the subtropical ridge, and the initial motion is west-northwestward at 290/12 kt. A gradual turn to the northwest is expected later today as the cyclone passes well southwest of Jamaica, followed by a north-northwestward motion that brings the center of Ian west of the Cayman Islands on Monday and near or over western Cuba by early Tuesday. There is relatively high confidence in this portion of the track forecast. However, once the cyclone emerges over the southeastern Gulf of Mexico, the spread in the track guidance increases at days 3-5. The HWRF and GFS still lie on the western side of the guidance envelope and show Ian moving over the central or western Florida panhandle, while the ECMWF and UKMET models show a track farther east into west-central Florida. Overall, the NHC track forecast remains near the center of the guidance envelope and still lies very near the TVCA multi-model consensus. However, there is still significant uncertainty in the long-range track forecast of Ian, and future adjustments to this portion of the forecast will likely be required. The atmospheric and oceanic conditions over the northwestern Caribbean Sea appear very conducive for significant strengthening. So once Ian becomes more organized, the high oceanic heat content and low vertical shear conditions appear likely to support rapid intensification. The Deterministic to Probabilistic Statistical Rapid Intensification Index (DTOPS) still shows a greater than 90 percent chance of rapid strengthening during the next 2-3 days. The intensity guidance remains very aggressive with strengthening Ian, and the NHC forecast reflects this potential. Ian is expected to become a hurricane by tonight or early Tuesday, and is forecast to reach major hurricane strength before it reaches western Cuba. This forecast lies very near the latest SHIPS guidance and the IVCN aid. By day 4, a significant increase in southwesterly shear is forecast by the global models, and this is forecast to induce some weakening as the vertical structure of the hurricane is disrupted. Despite this, 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 across the Florida Keys and Florida peninsula through mid 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, where a hurricane warning is now in effect. 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 the week, but uncertainty in the long-term track and intensity forecasts is 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 the 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 25/1500Z 15.2N 79.8W 45 KT 50 MPH 12H 26/0000Z 16.5N 81.1W 55 KT 65 MPH 24H 26/1200Z 18.1N 82.5W 70 KT 80 MPH 36H 27/0000Z 20.1N 83.7W 90 KT 105 MPH 48H 27/1200Z 22.0N 84.4W 105 KT 120 MPH 60H 28/0000Z 23.9N 84.8W 115 KT 130 MPH 72H 28/1200Z 25.5N 84.8W 115 KT 130 MPH 96H 29/1200Z 28.0N 84.4W 95 KT 110 MPH 120H 30/1200Z 30.3N 83.7W 65 KT 75 MPH...INLAND $$ Forecaster Reinhart |
