The Hurricane Boundary Layer Transition from Ocean to Land: A Multi-Platform Investigation of Hurricane Irene (2011)

The structure of the hurricane boundary layer (HBL) is important to characterize at landfall to better inform building design practice, catastrophe risk modeling, and operational forecasting. Often times, the necessary constellation of sensor data at landfall is absent to fully characterize the structure and evolution of the HBL as it transitions from deep ocean conditions to land. This lack of data forces engineers and meteorologists to make heuristic approximations regarding the structure of the HBL that account for ocean-to-land transitions. Recently, during the landfall of Hurricane Irene (2011), numerous aircraft, Global Positioning System (GPS) dropsonde, velocity-azimuth display (VAD), and in situ wind data were collected. The collation of this data for three time periods (i.e. open Atlantic, landfall interface, and overland) provides a unique opportunity to examine the structure and full evolution of Irene’s boundary layer as it transitions from deep ocean conditions to land. Thus, this research aims to (i) characterize the structure and evolution of Irene’s boundary layer as it transitions from ocean to land; and (ii) determine how well traditional methods predict Irene’s boundary layer shape during each time period.

Available wind data are rotated to a storm-relative coordinate system and composite analysis is used to examine HBL structural changes in Irene’s boundary layer during each composite time period. Traditional transition models are then employed to predict the shape of Irene’s boundary layer over the Atlantic Ocean, near the coastal interface, and overland. An evaluation of the performance of the transition models is conducted and discussion on model performance and potential improvements is provided.