Impact of compounding atmospheric events on shelf heat content in a river-influenced shelf system: Potential implications for Hurricane Michael

Hurricane Michael in 2018 was one of the strongest storms to impact the coastal U.S. and was unusual given that it occurred in October (i.e., late in the hurricane season) and intensified over the continental shelf. A potential contributor to this extreme event was thought to be anomalously high heat content on the shelf of the Mississippi Bight, a shelf region significantly impacted by freshwater discharge. Using available long-term time series of regional meteorological and oceanic measurements, water column conditions during the run-up to the rapid intensification of Hurricane Michael were compared to historical conditions in the region. Data for the water column heat content in the western Mississippi Bight were available at a mooring site on the 20 m isobath (Site CP) during August-October of 2018. Unusually high heat content was observed, relative to the typical summer conditions of previous years (N = 13), which resulted from the compounding effects of atmospheric events in the preceding months (Au...