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| #1161581 (Received by flhurricane at: 4:06 PM 17.Nov.2023) TCDAT2 Potential Tropical Cyclone Twenty-Two Discussion Number 5 NWS National Hurricane Center Miami FL AL222023 400 PM EST Fri Nov 17 2023 The disturbance continues to have a broad and elongated circulation with a vorticity maximum in the vicinity of western Jamaica and all of the associated deep convection east of the trough axis. Earlier ASCAT passes differed on the strength of the system`s winds, with the B instrument showing 35-40 kt within the Jamaica Channel and the C instrument only showing 25-30 kt. The intensity remains 30 kt based on a blend of these data. The system is accelerating northeastward with an initial motion of 050/15 kt. An additional acceleration toward the northeast--close to 30 kt by 36-48 hours--is expected as the disturbance gets picked up by a shortwave trough moving across Florida toward the southwestern Atlantic. The updated NHC forecast remains near the fastest model solutions, and is generally a blend of the previous forecast with the latest GFS model. As noted earlier, the disturbance`s motion across the Greater Antilles is likely to be discontinuous. The chance for the system to become a tropical cyclone continues to decrease and in fact now appears unlikely due to a combination of the system`s broad structure, the terrain of the Greater Antilles, strong southwesterly shear, and mid-level dry air. However, with the strongest surface winds near or just below 35 kt, there is still some chance that the system could produce tropical-storm-force winds over areas within the tropical storm watch, especially within heavy rainfall. The NHC forecast still shows the possibility, albeit small, for the system to become a tropical storm in 24-36 hours mainly based on continuity. After that, the system should become extratropical by 48 hours and absorbed by a front by 60 hours. Advisories on this system could be discontinued at any time if there is no longer a risk of tropical-storm-force winds within the tropical storm watch areas. Despite the decreasing chance of tropical cyclone formation, there is high confidence that heavy rainfall and flooding will remain a distinct and serious threat across Jamaica, southeastern Cuba, and Hispaniola. Additional rainfall amounts of 4 to 8 inches, with isolated areas as high as 16 inches, are forecast in these areas and are likely to produce life-threatening flash flooding and mudslides. KEY MESSAGES: 1. Potential Tropical Cyclone Twenty-Two could produce tropical storm conditions, especially in areas of heavy rainfall, across southeastern Cuba, Haiti, the southeastern Bahamas, and the Turks and Caicos Islands through Saturday, and tropical storm watches are in effect for these areas. 2. Heavy rains will impact portions of Jamaica, southeast Cuba, and southern Hispaniola through Sunday. This rainfall is likely to produce flash flooding, along with mudslides in areas of higher terrain. Lighter amounts across the southeastern Bahamas as well as the Turks and Caicos Islands may lead to flash flooding in urban areas. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 18.7N 77.7W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 18/0600Z 20.7N 75.3W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 24H 18/1800Z 23.4N 71.3W 35 KT 40 MPH...TROPICAL STORM 36H 19/0600Z 26.5N 66.0W 35 KT 40 MPH 48H 19/1800Z 30.1N 60.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 60H 20/0600Z...ABSORBED BY A FRONT $$ Forecaster Berg |
