Federal officials: UF engineers’ hurricane data vital to monitoring Isabel

September 24, 2003

GAINESVILLE, Fla. — Federal hurricane forecasters and emergency managers had an unprecedented up-close, real-time view of Hurricane Isabel’s windy fury as the storm moved ashore last week, thanks in part to four mobile weather towers operated by the University of Florida and Clemson University.

Deployed in North Carolina in or near Wilmington, Atlantic Beach, Cape Hatteras and Elizabeth City, the towers recorded the highest wind speed of any “continuous, high frequency, digital observations” of a hurricane making landfall, said Mark Powell, an atmospheric scientist at the National Oceanographic and Atmospheric Administration, or NOAA. The data the towers provided, transmitted via wireless technology, resulted in a more-accurate map of the approaching hurricane’s wind speeds and forces – information tapped by forecasters and emergency managers tracking Isabel and also expected to prove useful in future hurricane research, said Powell and other NOAA officials.

“We’ve never had high-quality information like this actually during an event,” Powell said. “It was just incredible how well these towers worked.”

The UF/Clemson research was part of a five-year effort aimed at gathering new information not only about how to better predict what will happen in hurricanes, but also how to construct buildings that will better withstand the massive storms. Isabel was the first storm in which the researchers also sent the data they collected electronically in real time to federal authorities.

Two of the 30-foot-tall wind towers, built atop mobile trailers, are based at Clemson University in South Carolina and two in Gainesville. Headed by UF civil engineering Associate Professor Kurt Gurley and composed of graduate and undergraduate civil engineering students, the UF team left Gainesville Sept. 15 as the storm approached. They arrived on the central coast of North Carolina the next day – two days before Isabel was predicted to make landfall – and deployed one tower in a state park near the small town of Atlantic Beach south of the expected landfall site. They set up the second tower in Wilmington south of Atlantic Beach the next day.

The Clemson team deployed its towers at Nag’s Head, near Cape Hatteras on North Carolina’s Outer Banks, and New Elizabeth, farther north. Most of the UF team stayed in Wilmington while the Clemson team bunkered down in New Elizabeth.

When Isabel came ashore the afternoon of Sept. 18, instruments on the towers monitored low-level wind speed, wind direction, barometric pressure and other conditions. Using a system designed by civil engineering graduate student Forrest Masters, the towers analyzed data every 15 minutes, determining, among other things, the peak wind speed during each period. They then uploaded that data via cellular technology to a Web site, where NOAA and National Hurricane Center authorities picked it up.

“That meant the data they got from us was no more than 15 minutes old,” Gurley said, adding that the team was pleasantly surprised the system worked so flawlessly in such rough conditions.

“There are so many things that can go wrong in an uncontrolled environment – the equipment can malfunction, the instruments can get hit by flying debris,” he said. “We were hoping to have one system working, and so to have all four working is really a tribute to Forrest’s work.”

Researchers at NOAA’s Hurricane Research Division added the data to the surface wind analysis map – known as H*Wind – which also relies on data from airborne sensors, offshore monitoring stations and radar systems. When combined with other data from mobile Doppler radar systems, the result was a more accurate real-time map pinpointing the location of Isabel’s most damaging winds and the extent of its gale-force winds, NOAA officials said.

“We typically use the existing network of conventional observing platforms, but they have limitations – some don’t have backup power, and some have questionable exposures,” Powell said, explaining that data from instruments located on a rooftop, for example, may be skewed because of the roof’s influence on wind speed.

Powell added that H*Wind is an experimental project produced at the National Hurricane Center in Miami and is being developed for operational use. The Federal Emergency Management Agency already uses information from the map to estimate the kind of structural losses that may result from hurricane wind damage, he said. Thanks to the UF/Clemson towers, NOAA was able to provide timely advance projections of peak wind velocities at numerous census track locations in Isabel’s projected path. FEMA has an inventory of the structures in each track location, allowing the agency to estimate the projected damage in each census track, he said.

Gurley said the towers also collected reams of data that will prove useful in ongoing hurricane research. For example, the team deployed two small “satellite” towers with each of the main towers in Wilmington, south of Isabel’s landfall, and Nag’s Head, north of it. The resulting data will paint a lateral picture of the wind showing how large and consistent the wind gusts turned out to be, Gurley said. He noted that the towers’ positions means the data will reflect the wind moving from land to water and vice versa.

“Having one tower gives us longitudinal data as the wind passes the instrument, but having multiple towers within several hundred feet allows us to capture the width of the gusts, which is important when relating wind behavior to house damage,” he said.