Influence of Potential Vorticity Structure on North Atlantic Tropical Cyclone Activity

Tropical cyclones are among the most devastating natural phenomena that can cause severe damage when hitting land. Some of this damage could be prevented with more reliable short-term and seasonal forecasts. In the wake of the poorly forecast 2013 North Atlantic hurricane season, Rossby wave breaking has been linked to tropical cyclone activity measured by the accumulated cyclone energy. Here, ERA5 reanalysis data and HURDAT2 tropical cyclone data are used to show that the latitude of the 2 potential vorticity unit (PVU) contour on the 360 K isentropic surface in the western North Atlantic is linked to changes in vertical wind shear and relative humidity during the month of September.

A more equatorward position of the 2 PVU contour is linked to an increase in vertical wind shear and a reduction in relative humidity, as manifested in an increased ventilation index, in the tropical western North Atlantic during September. The more equatorward position of the 2 PVU contour is further linked to a reduction in the number of named storms, hurricane days, hurricane lifetime, and number of tropical cyclones making landfall due to changes in genesis location. In summary, the 2 PVU contour latitude in the western North Atlantic can therefore potentially be used as a predictor in seasonal and sub-seasonal forecasting.