Sean — 2023

Sean formed from a tropical wave that moved off the west coast of Africa on 5 October and became a tropical depression at 1800 UTC on 10 October 2023. It moved generally west-northwestward across the central tropical Atlantic and existed as a tropical cyclone through about 16 October, dissipating by 0000 UTC on 17 October. The system was mostly sheared and asymmetric during its life, with stronger winds confined to its northern side. Sean did not make any landfalls. It remained over open water for its entire lifespan and produced no reports of tropical-storm-force winds at any ships or land stations. The storm’s peak intensity was estimated at 40 knots (46 mph) with a minimum central pressure of about 1005 millibars, corresponding to a moderate tropical storm (below hurricane strength). Peak winds occurred around 1800 UTC 12 October and persisted through 0000–0600 UTC 13 October in the best-track record. Because Sean stayed far from land, there were no coastal storm surge measurements or rainfall impacts reported in the NHC report. No surge heights or rainfall totals at cities or counties were recorded. There were no reports of damage or casualties associated with Sean; the report lists no direct fatalities and no reported impacts on land. Regions most affected were none, since the storm remained over the open tropical Atlantic. Notable items: the NHC had included the system in its Tropical Weather Outlook well in advance (first mention about 138 hours before formation), and official intensity forecasts were more accurate than recent 5‑year averages. No watches or warnings were required.