The wrath of a hurricane is an unknown demon to the Wisconsin climate and not much more than a headline in the concerns of the average Madisonian. UW atmospheric scientist Chris Velden and PhD candidate Robert Wacker are the exception.
Velden heads the Tropical Cyclone Research Group at the Cooperative Institute for Meteorological Satellite Studies and sits at the forefront of tropical storm research hundreds of miles from the havoc and bluster of hurricanes Charley and Frances.
To UW students, CIMSS is a goliath of a satellite dish on Dayton Street. For meteorologists and Federal Emergency Management, this division of the UW Space Science and Engineering Center is a guardian angel.
Velden’s work with CIMSS began as a UW Masters student in the early ’80s. Through his thesis work, he pioneered complex techniques for measuring storm intensity through microwaves emitted from around the storm wall. Today satellite-imaging techniques utilize microwaves emitted from the atmosphere in and around the storm.
During the height of Charley and Frances’ approaches toward the Florida coast, the TCRG’s techniques, using special McIDAs software developed by SSEC for satellite research, helped the National Hurricane Center direct emergency managers in Florida cities.
TCRG techniques and their website also allowed Florida residents to follow both storms’ path on the web.
“We had around 3 million hits a day during the height of Frances,” Velden said. “Our website works as a direct public outreach tool.”
Velden likens the formation of a hurricane to an Olympic skater “bringing in her arms and spinning faster and faster.”
“As it tightens it gains vorticity. This is what made Charley particularly devastating. It’s eye contracted to about a two-mile radius,” Velden said.
TCRG is helping hurricane researchers better understand what causes a storm’s intensity to grow.
Before Velden developed his techniques of imaging hurricanes through microwaves, satellites provided data largely limited to storm direction. Velden’s algorithms opened a discovery gateway that allows scientists to gather other data via satellite that historically could only be gathered by airplanes entering the storm’s eye.
“This was limiting because storms could only be studied as they approached land, not far out in the ocean,” said Wacker, a PhD student on Velden’s team.
Wacker, a United States Air Force weather officer, is currently working to improve the quality of microwave data received by satellites and the statistical interpretation of the data developed by Velden’s team.
CIMSS satellite-based wind shear measurements also helped the National Hurricane Center see the vertical wind shear forces that broke Frances’ spiraling caterwaul and reduced it from a category 4 to a category 2 storm.
“[However], the NHC had to be careful about telling people on the ground that the force of the storm was diminished because it could surge again,” Velden said. “Just because data changes the interpretation for meteorologists, we have to keep people prepared for worst case scenario.”
Wacker hopes to correct the small inaccuracies in the current technique of gathering hurricane data.
Microwaves emitted from warmer areas in the storm provide radiation readings that allow the satellite to see the formation of the storm. They also help meteorologists understand the changing intensity of the storm. Heavy thunderstorms around the eye of the hurricane cause minor interference with microwave frequencies being read by the satellite.
“The light photon of the microwave is redirected when it encounters a raindrop or hailstone of a certain size,” Wacker explained. “This creates an effect called scattering and can result in a reading that is a 10th of a degree or a couple of degrees off.”
Wacker hopes his fine-tuning can lead to better simulation models, something that could benefit the state of Florida, currently staring at a multi-billion dollar mess from Charley’s wrath.
