Doppler Profiler Observations of the Boundary Layer within the Eyewall of Hurricane Georges during Landfall

Detailed wind profiles and other boundary layer (BL) properties of Hurricane Georges, during its landfall on the Mississippi coastline, are described using measurements from a mobile Doppler profiling system (915 MHz profiler, Doppler sodar, and ceilometer). During maximum wind conditions, the wind profile within the eyewall assumed the form of a jet, with peak winds of 44 m s-1 with the 0.5-1.0 km AGL layer. Considerable shear existed above and below this jet core. We define the BL depth as the region within which turbulence is enhanced. We find that the BL depth is roughly proportional to the BL wind magnitude, and attained a height of about 2 km AGL during maximum measured winds 45 m s-1 within the 0.5-1.0 km AGL layer. The BL contains resolvable eddies, consisting of updrafts and downdrafts of 1-3 m s-1 magnitude, that may be associated with the vertical branches of horizontal convective rolls recently identified within landfalling hurricanes. These turbulent eddies, and the large vertical shear of horizontal winds within the BL, appear to produce a uniform mass concentration of relatively small raindrops within the BL. Measurements of cloud base height also reveal large fluctuations within this turbulent cloud-filled hurricane BL.