A Climatology of Tropical Cyclone Wind Field Asymmetry Postlandfall and an Examination of the Factors Influencing That Evolution

Several landfalling major hurricanes across the Gulf Coast over the past two decades (e.g., Katrina, Ivan, Charley, Michael) have reemphasized the importance of correctly analyzing and forecasting the intensity of the wind field leading up to and after landfall. However, comparatively little work has focused on how the wind field asymmetry (or lack thereof) changes at and after landfall. This evolution is important to understand in order to better prepare the inland population to wind speeds rarely seen inland but commonly seen at the coast.

Accordingly, this presentation will examine the evolving wind field asymmetry of 30 landfalling tropical cyclones (TCs) across the southern coastal U.S. during the period 2004-2018. Examples of the variety of the evolving post-landfall asymmetry will be presented, followed by a statistical analysis of the climatology of the evolution. Finally, we will examine factors that may influence the variability in the post-landfall wind field decay and its asymmetry with the goal of better understanding and predicting this part of the TC lifecycle. These factors will include specifics of the TC itself (speed of motion, time of year, size, intensity) as well as environmental factors such as synoptic meteorological pattern, surface land type and terrain, and factors that conflate these two – such as occurred with Harvey when the slow speed of motion lead to a dramatic change in the underlying surface type due to excessive rainfall.