How risk modelers tracked Hurricane Ian's growing intensity

A quiet North Atlantic hurricane season kicked into life Wednesday as Hurricane Ian made landfall in southwest Florida as a high-end Category 4 major weather event. This is the ninth tropical storm of the current season and the fourth hurricane. Early in the day, 18 counties in Florida had issued mandatory or voluntary evacuation orders. National Hurricane Center (NHC) forecasts indicated the eye of Hurricane Ian moved over south-central Florida as it headed north toward the Carolinas.

Dramatic images from the storm included the Tampa Bay emptying out as the storm sucked water toward the ocean, and then the reverse happening later in Fort Meyers, as storm surge washed over the city.

Comparing this season to 2021, the ninth storm was Hurricane Ida in late August, and it was the most destructive of that year.

Ian first flexed its muscle Tuesday (Sept. 27, 2022) when it made landfall near La Coloma on the southwest coast of Cuba as a Category 3 major hurricane. At that time, Ian had maximum sustained wind speeds of 125 miles per hour (205 km/h). Damages are currently being assessed, but an immediate impact from Ian was reported from the Cuban state electric company, Unión Eléctrica de Cuba, declaring a total power blackout for 11 million citizens.

Since passing over Cuba, Ian has defied early forecasts and continued to intensify over the warm waters of the Gulf of Mexico into a high-end Category 4 major hurricane, with maximum sustained winds of 155 miles per hour (250 km/h), just two miles per hour shy of Category 5 intensity.

Some fluctuations in intensity are possible as Ian barrels north and then move into central Florida tonight and Thursday morning, before emerging over the western Atlantic by late Thursday.

The RMS HWind team is issuing regular snapshots, footprints and forecasts to RMS clients for Hurricane Ian, and the HWind wind field snapshot (pictured at right) from midday Wednesday shows how Hurricane Ian continued to intensify throughout the day.

Examining the HWind snapshot, the hurricane’s wind field had approximately 47 terajoules (TJ) of integrated kinetic energy Wednesday morning, which is comparable to the levels found in Hurricanes Michael (2018) and Laura (2020). Tropical storm force winds extended out some 150 miles (241 kilometers).

Catastrophic wind damage is likely where the core of Ian moves onshore and will weaken after landfall. Hurricane-force winds are expected throughout the storm.

The combination of storm surge and the tide caused normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The deepest water will occur along the immediate coast near and to the right of the storm’s center, where the surge will be accompanied by large waves. Water levels were believed to reach 12 to 16 feet (2.4 to 3.6 meters) in the region between Longboat Key and Bonita Beach, including Charlotte Harbor.

Heavy rainfall will spread across Florida through Thursday. Widespread, life-threatening catastrophic flooding is possible across portions of central Florida with considerable flooding in southern and northern Florida.

Risk managers and response personnel like those at RMS must keep clients well informed of Hurricane Ian developments and their possible implications in terms of loss.

James Cosgrove (james.cosgrove@rms.com) is a senior modeler with the event response team at the catastrophe risk modeling company, RMS. The original version of this article first published at rms.com and is republished here with permission.

Executive Editor Elana Ashanti Jefferson contributed to this report.

Also by this contributor: Florence landfall forecast: A new twist