Isaac — 2024

Isaac formed from an extratropical low that lost its frontal features and became a tropical cyclone on 25 September 2024 about 515 nautical miles northeast of Bermuda. It existed as a tropical cyclone from 25 to 30 September, moving generally northeastward across the North Atlantic before transitioning back to an extratropical system on 30 September and dissipating a few days later. Key milestones include its tropical transition on 25 September and a period of strengthening to hurricane status on 27 September, followed by weakening after its peak on 28 September. The storm did not make landfall and there were no coastal watches or warnings issued. Isaac remained well offshore for its entire lifetime and produced no reports of tropical-storm-force winds at ships or on land. Isaac’s maximum sustained winds peaked at 90 knots (about 104 mph) from 0600 to 1200 UTC on 28 September, with an estimated minimum central pressure of 963 mb. At peak it was a Category 2 hurricane on the Saffir–Simpson scale. Because Isaac stayed over the open ocean, there were no reported storm surge measurements or rainfall totals for coastal cities or counties in the NHC report. No ship or land observations of tropical-storm-force winds, surge, or heavy rainfall were recorded in association with Isaac. There were no reports of damage or casualties—no direct fatalities and no reported indirect fatalities—linked to Isaac. The report notes no impacts on populated areas. Noteworthy items: Isaac’s formation was not well predicted in advance — the precursor low was first mentioned in the NHC Tropical Weather Outlook only about 12 hours before tropical cyclone formation. NHC track forecasts through 60 hours were generally better than recent five-year averages, while intensity forecasts were comparable to recent norms.