Steering of MDR-Originating Tropical Cyclones: Landfall or Recurvature?

While the majority of tropical cyclones (TCs) that make landfall in the CONUS form in the Gulf of Mexico, a substantial portion of landfalling TCs commence in the main development region (MDR) of the North Atlantic Ocean. It is generally understood that the steering of these MDR-originating TCs is impacted by various synoptic-scale phenomena, such as the Bermuda High and easterly trade winds. It is still difficult, however, to predict whether Atlantic TCs recurve northward or continue westward to eventually make landfall in the Americas. Thus, the current study evaluates the environments of both groups: TCs that either make landfall or recurve without landfall.

To objectively sort TCs, a K-means clustering method is implemented that takes into account the track shape, length, and location in addition to the along-track TC intensity. All Atlantic basin TCs that occurred during 1940–2022 and reached at least tropical storm intensity are included, derived from the HURDAT “best-track” dataset. Two of the six resulting clusters depict MDR-originating TCs that either make landfall in Central or North America, or recurve northward without making landfall. The landfall cluster, which includes 55 TCs, peaks in frequency during late August and early September, with a steep decline in late September. The recurve cluster, 105 TCs, peaks in late September, with a more gradual decline in frequency through late October. Results derived from ERA5 reanalysis will focus on the steering mechanisms that are distinct between the landfall and recurve clusters. Discussion on synoptic-scale steering patterns will largely emphasize SLP and 500-hPa geopotential heights and winds.