Recent studies have confirmed that a wind speed maximum is found near the top of the tropical cyclone boundary layer. This maximum is associated with a low-level supergradient inflow in the boundary layer owing to the strong inward advection of angular momentum. The downward transport of additional momentum associated with the low-level jet can result in extensive surface damage. Hence, understanding this low-level feature is important to operational forecasts and warnings, and should be considered in the building of high-rise structures. NOAA Hurricane Research Division dropsonde data and Weather Research and Forecast (WRF) model simulations are used to investigate the boundary layer wind field of Hurricane Ike (2008) during the period between the landfall of Ike on Cuba and its subsequent landfall on the Texas coast. The spatial and vertical variability of the boundary layer winds in Ike agree with the current theoretical concepts, and the flow in the middle to upper boundary layer near the eyewall is found to be supergradient. As Ike approaches the Texas coast and makes landfall, the low-level jet becomes 25% - 40% supergradient in the dropsonde data and WRF simulations, much higher than the 10% - 20% supergradient in a pure marine boundary layer.
