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OU Researchers Collect Data From Hurricane Sally

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September 17, 2020

OU Researchers Collect Data From Hurricane Sally

•	Image of the vertical cross-section through the eyewall of Hurricane Sally showing winds exceeding 90 mph along the inner edge of the eyewall.

NORMAN, OKLA. – University of Oklahoma scientists led by Michael Biggerstaff, OU School of Meteorology professor, deployed a Shared Mobile Atmospheric Research and Teaching (SMART) weather radar south of Mobile, Alabama, in advance of the landfall of Hurricane Sally. There they measured the structure of the winds in the hurricane boundary layer, the lowest mile of air above the ground.

The project was funded by the National Institute for Standards and Technology to capture the vertical profile, duration and gustiness of extreme winds in an effort to improve building codes to mitigate damage to homes and commercial buildings. 

As of Wednesday, Sept. 16, the team has conducted 24 hours of continuous observations.

“Never before have radar-derived total winds been collected for so many hours within the same portion of a hurricane,” said Biggerstaff. “Since stability of the boundary layer changes with solar heating and nocturnal cooling, this long data record will allow our group to study how changes in the ability of atmosphere to transport higher energy air from aloft to the surface changes the potential for damage from these severe windstorms.” 

•	Photo of OU SMART radar deployment site south of Mobile, Alabama, during Hurricane Sally.

He adds that normally hurricanes move too fast to sample the same areas for an entire day, but the lack of largescale steering patterns led Sally to slowly drift offshore while it maintained its strength. 

Research team members also recently collected wind speed data from Hurricane Laura just three weeks ago.

Biggerstaff said, “we want to help mitigate property damage by working with engineers and using our data to improve the building and construction codes needed to develop a more resilient national infrastructure in the future.”

Biggerstaff and doctoral student Addison Alford recently published their findings from a similar deployment during the landfall of hurricane Irene in 2011 over the coast of North Carolina. In that study they measured how the strongest winds in the hurricane rose over the coastal land and ocean water interface and how downdrafts in the rainbands were more effective in producing strong wind bursts in the outer bands than the inner core. Since Irene moved quickly, it wasn’t possible to determine if the difference in damage potential in the outer bands and to the inner core was related to fundamental characteristics of the circulations within the hurricane or changes in the stability of the atmosphere as solar heating yielded to nocturnal cooling. 

“Fortunately, the combination of Hurricane Sally’s slow movement and the geography of Mobile Bay and adjacent land areas will allow us to unravel the influence of solar heating on the potential for damaging winds from aloft to get mixed down to the surface and how that changes in association with the transition from water to land,” Biggerstaff said.