Boundary Layer Characteristics in Hurricanes Bonnie (1998), Dennis (1999), and Floyd (1999) as determined from the Texas Tech University Wind Engineering Mobile Instrumented Tower Experiment (WEMITE)

The Texas Tech University Wind Science and Engineering Research Center has constructed and deployed two mobile instrumented towers in order to better document and understand the turbulent structure of the hurricane planetary boundary layer. Both WEMITE towers measure atmospheric conditions employing a relatively quick sampling rate (5-10 Hz) and are approximately 10m in height. WEMITE 1 was constructed in 1998 and deployed in both the 1998 and 1999 Atlantic Hurricane Seasons, while WEMITE 2 was completed in the early summer of 1999.

Hurricanes Bonnie, Dennis, and Floyd each made landfall on the North Carolina coastline. The WEMITE towers obtained data from Bonnie and Floyd as they made landfall near Cape Fear, and Dennis as it moved just south of the Carolina coastline on its first approach to the US mainland. While the recorded wind speeds in each event were essentially equivalent with the WEMITE deployment sites measuring wind speed gusts of approximately 39 m/s, each of the storms were characteristically different. Hurricane Dennis, which did not make landfall on its first pass, and Floyd, were more convectively active than compared with the stratiform nature of Bonnie at landfall. Both Bonnie and Floyd were in a state of decay as they approached the coastline, while Dennis was not; and while Bonnie slowly moved northward at landfall, Dennis and Floyd were moving relatively rapidly. These differences offer a unique opportunity to examine the relationship of turbulent parameters such as integral scales, turbulence intensities, and gust factors with different storm characteristics and deployment locations (exposures).