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| #1108664 (Received by flhurricane at: 4:56 AM 24.Sep.2022) TCDAT4 Tropical Storm Ian Discussion Number 5 NWS National Hurricane Center Miami FL AL092022 500 AM EDT Sat Sep 24 2022 Ian is still being affected by some north-northeasterly, however short-wave infrared imagery suggests that the center is located beneath the eastern edge of the colder convective cloud tops. Deep convection over the western portion of the circulation has increased overnight but there is still little banding evident in conventional satellite imagery. Subjective Dvorak satellite classifications from TAFB and SAB, and objective estimates from UW-CIMSS have changed little this cycle, but given that the center is more involved with the deep convection, the initial intensity has been increased to 40 kt, which is between the objective estimates and a TAFB Dvorak T-number of 3.0 or 45 kt. A NOAA Hurricane Hunter aircraft is scheduled to investigate Ian this morning, and should provide additional data on Ian's structure and intensity. Recent satellite fixes indicate that Ian has turned westward (270/12 kt) overnight to the south of a narrow ridge centered near Hispaniola. By early Sunday, Ian is expected to reach the western portion of the ridge, and the storm should turn west-northwestward, and then northwestward over the northwestern Caribbean in 36 to 48 hours. After that time, Ian is forecast to turn north-northwestward and northward around the western portion of the ridge. This will bring Ian near or over Western Cuba and into the southeastern Gulf of Mexico. Late in the period, the guidance indicates the storm will begin to recurve toward Florida. As mentioned before, the track models are in general agreement with this scenario, however there is a large amount of cross-track spread at 72 hours and beyond. In fact, the east-west spread in the guidance at 96 hours is about 180 n mi, with the CTCI and ECMWF along the eastern side of the envelope, and the GFS, HWRF, and GFS ensemble mean along the western side. The overall guidance envelope has shifted slightly westward this cycle, and the NHC track has been nudged in that direction and lies just east of the various consensus aids. Given the spread in the guidance, and the still shifting dynamical models, additional adjustments to the track forecast may be needed in subsequent advisories. Users are reminded that the long-term average NHC 4- and 5-day track errors are around 150 and 200 n mi, respectively. The shear that has been plaguing Ian is forecast to continue to decrease over the next day or two while the cyclone moves over the warm waters of the central and northwestern Caribbean Sea. This should allow for strengthening, with steady to rapid intensification (RI) quite possible once an inner core becomes established. Although the updated NHC forecast is just shy of forecasting RI (30 kt or greater increase over 24 h) during any 24-h period over the next few days, it calls a 45-kt increase in wind speed between 24 and 72 hours, and Ian is likely to be near major hurricane intensity when it approaches western Cuba. Since Ian is not expected to remain over Cuba long, little weakening is expected due to that land interaction, and the forecast again shows Ian as a major hurricane over the eastern Gulf when it is approaching the west coast of Florida. Key Messages: 1. Ian is expected to produce heavy rainfall and instances of flash flooding and possible mudslides in areas of higher terrain, particularly over Jamaica and Cuba. 2. Hurricane conditions are possible in the Cayman Islands by early Monday, with tropical storm conditions possible by late Sunday. Tropical storm conditions are possible in Jamaica on Sunday. 3. Early next week, Ian is forecast to move near or over western Cuba as a strengthening hurricane and then approach the Florida peninsula at or near major hurricane strength, with the potential for significant impacts from storm surge, hurricane-force winds, and heavy rainfall. While it is too soon to determine the exact magnitude and location of these impacts, residents in Cuba, the Florida Keys, and the Florida peninsula should ensure they have their hurricane plan in place and closely monitor forecast updates through the weekend. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 14.7N 73.5W 40 KT 45 MPH 12H 24/1800Z 14.6N 75.2W 45 KT 50 MPH 24H 25/0600Z 15.2N 77.4W 50 KT 60 MPH 36H 25/1800Z 16.5N 79.4W 60 KT 70 MPH 48H 26/0600Z 18.2N 81.0W 70 KT 80 MPH 60H 26/1800Z 20.2N 82.4W 85 KT 100 MPH 72H 27/0600Z 22.0N 83.3W 95 KT 110 MPH 96H 28/0600Z 25.5N 83.3W 100 KT 115 MPH 120H 29/0600Z 28.2N 82.1W 85 KT 100 MPH...INLAND $$ Forecaster Brown |
