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Tropical Storm Iota Forecast Discussion Number 2
2020-11-13 21:44:48| National Hurricane Center (Atlantic)
Issued at 400 PM EST Fri Nov 13 2020 000 WTNT41 KNHC 132044 TCDAT1 Tropical Storm Iota Discussion Number 2 NWS National Hurricane Center Miami FL AL312020 400 PM EST Fri Nov 13 2020 Banding features over the eastern and southeastern portions of the cyclone's circulation have increased since this morning, and the overall organization of the system continues to quickly improve. Earlier ASCAT data indicated that there was a fairly large area of light winds near the center, and that the low-level center was displaced to the northwest of the mid-level center seen in visible satellite imagery. Since the system is still in its formative stage, the low-level center may reform closer to the mid-level feature, and the advisory position is a compromise between the low- and mid-level circulations. The earlier ASCAT data indicated peak winds of around 30 kt with several higher rain-inflated vectors. Based on the continued increase in organization, and Dvorak T-numbers of T2.5 from both TAFB and SAB, the initial intensity is raised to 35 kt. Iota becomes the 30th named storm of the recording-breaking 2020 hurricane season. The environment ahead of Iota appears to be quite conducive for intensification. The system will be moving over warm waters, in a moist atmosphere, and within an area of very low vertical wind shear. As a result, steady to rapid strengthening appears likely over the next few days. The NHC intensity forecast calls for Iota to reach hurricane status within 36 h, and now calls for the system to be a major hurricane when it approaches the coast of Central America. The NHC intensity foreast is in good agreement with the HFIP corrected consensus model, and the 70-kt increase in intensity over the next 72 hours is supported by the SHIPS Rapid Intensification Index that shows a nearly 60 percent chance of a 65 kt increase in intensity during that time period. The tropical storm has not moved very much today, and the initial motion estimate is a somewhat uncertain 255/3 kt. A strong mid-level ridge that extends across Florida and the western Atlantic is forecast to slide eastward over the next few days causing the cyclone to move faster toward the west or west-northwestward. The track guidance has come into a bit better agreement this afternoon, with only the HWRF showing a track farther north over the northwestern Caribbean Sea. The latest consensus aids were very close to the previous official forecast, and no significant adjustments to the earlier track forecast were required. Key Messages: 1. Iota is expected to strengthen and be a major hurricane when it approaches the coast of Central America. There is a risk of dangerous wind, storm surge, and rainfall impacts across portions of Nicaragua and Honduras beginning Sunday night or early Monday. Hurricane Watches will likely be issued for a portion of this area tonight or early Saturday. 2. Through Wednesday morning, heavy rainfall from Iota may lead to life-threatening flash flooding and river flooding across portions of Haiti, Jamaica and Central America. Flooding and landslides from heavy rainfall could be significant across Central America given recovery efforts underway after Hurricane Eta. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 13.8N 74.3W 35 KT 40 MPH 12H 14/0600Z 13.7N 75.1W 45 KT 50 MPH 24H 14/1800Z 13.7N 76.2W 55 KT 65 MPH 36H 15/0600Z 13.9N 77.5W 70 KT 80 MPH 48H 15/1800Z 14.2N 79.3W 85 KT 100 MPH 60H 16/0600Z 14.6N 81.2W 95 KT 110 MPH 72H 16/1800Z 15.0N 82.8W 105 KT 120 MPH 96H 17/1800Z 15.2N 85.5W 50 KT 60 MPH...INLAND 120H 18/1800Z 14.7N 88.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown
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