Idalia — 2023

A tropical depression formed on 26 August 2023 over the Yucatán Channel about 40 nautical miles east-southeast of Cancún after a disturbance crossed Central America. The system became Tropical Storm Idalia the same day, moved northeast through the Caribbean and stalled briefly before turning north into the Gulf of Mexico. Idalia accelerated northward over very warm Gulf waters and rapidly intensified on 29–30 August, reaching major hurricane strength before weakening slightly prior to U.S. landfall. The cyclone tracked north-northeast across the Florida Big Bend, moved inland through southern Georgia and the Carolinas, became extratropical offshore North Carolina on 31 August, passed south of Bermuda on 2 September as a frontal system, and finally dissipated off Atlantic Canada on 8 September. Idalia made at least two notable landfalls. The storm’s circulation first crossed Cozumel, Mexico, on 27 August while a tropical depression. Its primary U.S. landfall occurred near Keaton Beach, Florida, around 1145 UTC 30 August as a major hurricane with estimated maximum sustained winds of 100 kt (115 kt peak earlier over water). After moving inland the storm weakened quickly and its center moved off the coast near Myrtle Beach, South Carolina, on 31 August with winds near 50 kt as it became extratropical. The storm’s maximum estimated intensity was 115 kt (132 mph) with a minimum central pressure of 942 mb at 0900 UTC 30 August, when Idalia was a category 4 hurricane over the Gulf of Mexico. Aircraft and instrument data supported that peak; an eyewall replacement cycle and some weakening occurred before the Florida landfall, so the best estimate at landfall was 100 kt (category 3). Storm surge was extreme along the Florida Big Bend. The largest analyzed inundation was 8 to 12 feet above ground level from Keaton Beach southward through Steinhatchee, with surveyed high water marks as high as 9.6 ft above typical high water near the Steinhatchee River and indications of 10–14 ft wave-affected marks at Keaton Beach. Horseshoe Beach and Cedar Key saw major surge and wave damage (Cedar Key tide gauge measured 6.89 ft above MHHW and a surge of about 8.91 ft above normal tides). Tampa Bay and Clearwater recorded elevated water levels (East Bay Tampa 4.56 ft above MHHW; Clearwater pier 3.86 ft above MHHW). Rainfall totals were widespread: much of the track from the Florida Big Bend into eastern North Carolina received 5–7 inches, with pockets of 7–10 inches in southern Georgia and South Carolina; Holly Hill, South Carolina, reported the highest total at 13.55 inches. Idalia caused 12 confirmed fatalities in the United States; 8 were classified as direct (all due to rough surf and rip currents: 1 in Florida, 3 in North Carolina, 3 in New Jersey, and 1 in Delaware) and 4 were indirect (two tree-related deaths during cleanup in Florida and Georgia, and two vehicle accidents in Florida). The estimated U.S. damage is about $3.6 billion (NCEI estimate), concentrated in Florida’s Big Bend and northern agricultural areas where storm surge, flooding, and destructive winds damaged homes, infrastructure, crops, irrigation systems, aquaculture, and livestock. Tornadoes associated with Idalia (12 total) produced additional localized damage in Georgia, South Carolina, and North Carolina. Noteworthy points include the rapid intensification of Idalia over the Gulf’s Loop Current to a category 4 before landfall, and that it became the third-strongest hurricane on record to hit Florida’s Big Bend region. Forecast track guidance and NHC official track forecasts performed well overall, with track errors below recent 5‑year means at many lead times; intensity forecasts captured the major strengthening and weakening phases reasonably well though early intensity forecasts showed a low bias. Storm surge warnings issued in advance verified in many locations, though the remoteness of the landfall area likely meant some highest surge values went unmeasured.