A new research paper documents the extreme environment across the Gulf of Mexico that allowed Hurricane Ian to explode in intensity. It details what caused the storm to rapidly intensify from a Category 3 to a 5 before hitting land in Southwest Florida on September 28, 2022. Yonggang Liu, an associate professor and the lead author of the study, led the research. It does emphasize the important role of warm, subsurface waters and points to a notable “pressure point” south of the Dry Tortugas.
Researchers said that before Hurricane Ian hit, surface temperatures in the Gulf were just 1-2°C above normal. Subsurface waters, though, told a much more alarming story, with temperatures 2-3°C above average. With both anomalies contributing greatly to the hurricane’s rapid intensification, they present important questions about forecasting techniques.
The Role of Ocean Currents
The West Florida Shelf tends to be kept at cooler temperatures because of the influence of prevailing ocean currents. Yet, at the climax of hurricane season, subsurface waters across this shelf were eerily warm. The Loop Current did not form a closed circulation pattern. That was the case with this latest issue, which happened in the shallow waters of the Gulf.
Liu emphasized that “typically, there is a mixing of the water column where warmer surface waters interact with the underlying, often cooler subsurface water.” Unfortunately, in this instance the Loop Current did not hit the “pressure point” that we had identified. Consequently, there was no influx of cold, deepwater from the heart of the Gulf to replace this unusually warm water on the West Florida Shelf.
The study’s results highlight how minimization of mixing led both surface and subsurface waters to remain abnormally warm throughout the summertime months. This warming trend contributed in the run-up to Hurricane Ian. This all combined to create a very deep layer of warmth which helped power the storm’s explosive intensification.
Understanding Temperature Dynamics
To better understand why warm subsurface waters lingered into the summer, the research team followed the trajectory of this water. Liu stated, “We wanted to understand how the warm subsurface waters of the West Florida Shelf were able to persist all summer.” Their research found that tracking just sea surface temperatures gives a limited view of available hurricane energy.
Liu remarked, “By not including the subsurface [water temperature] in models and forecasting, we are not getting the entire picture of the water column and the potential energy for hurricanes.” This one insight illustrates the need for more complete data collection, as this is critical to informing the most accurate hurricane forecasts possible.
Implications for Future Hurricane Predictions
The potential of these findings far-reaching, especially as we look to improve future hurricane forecasts. Better understanding of subsurface water temperatures could result in better forecasting models. Liu noted, “The more real-time observations we have of the entire water column, the better predictions we can provide, and the safer our communities will be.”
The study was published in Geophysical Research Letters and can be accessed via DOI: 10.1029/2024GL113192. This really drives home the great need for holistic and smart monitoring systems. Most importantly, it identifies strategic areas of the Gulf that might affect the behavior of an incoming hurricane.