Written by Jessica Gregg McNew, Staff Writer, DisasterRelief.org
As Hurricane Bonnie bears down on the Bahamas, a handful of researchers are monitoring the storm's track in anticipation of U.S. landfall and the opportunity to deploy an innovative new radar to better understand the physics of the storm.
Dr. Joshua Wurman, a professor of meteorology at the University of Oklahoma, could leave as early as Sunday with other researchers who work on the Doppler on Wheels (DOW), a portable radar system used to record data on hurricanes and tornadoes. Once Wurman and his team receive the green light from the National Oceanic and Atmospheric Administration's (NOAA) Hurricane Research Division and meteorologists at the University of Oklahoma, they'll take their DOW on the road. ``Basically, we race the hurricane to the coast,'' Wurman said.
Once there, the team will park two trucks equipped with the DOW radar 30 miles apart, establishing what's known as a dual Doppler baseline. That means that the two systems will be used to determine wind speed, as well as wind direction. If only one radar was used, scientists would not be able to determine wind direction.
DOW was first put into service in late 1994, but did not see any storm activity until spring 1995 when researchers used the Doppler to record data on a tornado. In 1996, Wurman and his team took DOW to North Carolina where it measured the wind speeds of Hurricane Fran as it slammed into the coast.
What they discovered on that trip was something hurricane researchers did not know about at the time and which Wurman discussed in an April 1998 issue of Science magazine -- boundary layer rolls or helical shapes that spiraled horizontally in the hurricane in alternating streaks of higher and lower wind speeds. Winds in one roll might blow at 100 mph, while another roll might have winds speeds of 60 mph. By deploying DOW in a hurricane this year, Wurman hopes to study this phenomenon more.
He also hopes to understand the physical changes a hurricane undergoes as it makes landfall, and learn whether certain tropical storms will cause flooding in one area versus another. ``[Landfall] is a very catastrophic time for the storm,'' Wurman noted.
In addition, Wurman hopes to determine if tornadoes are embedded in the eyewall of a hurricane and to correlate wind speeds with damage. The latter is important because after a storm as devastating as Hurricane Andrew hits, it's hard to determine what caused the damage.
Earlier this year, DOW recorded wind speeds of 246 mph near Spencer, S.D., where a tornado essentially destroyed the entire town. Tornadoes are measured by the Fujita wind scale, which categorizes the storm based on the damage it caused rather than wind speed measurements. ``If a 300 mph tornado goes through a wheat field, it's still an F-0 tornado,'' Wurman said, because property damage is minimal.
The DOW measurement in South Dakota marked the first time that the wind speed of a tornado was measured in an area where it caused damage. That's important because, again, it allows researchers to determine how a tornado can damage a community, information that becomes valuable to mitigation experts.
For all the data it collects, however, the DOW is unable to provide real-time information that could be used to help prepare residents for an approaching storm. As Wurman notes, if residents secure their homes and seek shelter when a hurricane warning is issued, how useful is it be told that a hurricane-spawned tornado is headed toward their neighborhood. ``What are you going to do different than you are if you're already hiding under a desk?'' he said.
Transported in a heavy truck with steel mesh over its glass surfaces and hydraulic feet to secure it in place, the DOW can withstand winds up to 150 mph. Wurman doesn't want to take the system into a storm with stronger winds out of fear that blowing debris could damage its equipment.
Researchers on the data-gathering mission will keep in constant contact with forecasters and will be able to monitor conditions themselves. If the hurricane spawns a tornado headed toward the team, they will likely be able to spot it and evacuate the area before danger approaches. No one is out to reenact a scene from the movie ``Twister,'' Wurman said, adding, ``We think we are as safe as we can be given that we're going into a hazardous situation.''
Also in the race to beat a hurricane to the coast is John Schroeder, a graduate student at Texas Tech University, who will transport a 35-foot-high steel tower equipped with wind sensors. Secured to a trailer and buttressed by guy wires, the tower can be assembled in an hour or less and can withstand 130-150 mph winds.
The tower's sensors, placed at 10-foot increments, will take measurements every quarter of a second. Through this data, Schroeder and other Texas Tech researchers hope to better understand the turbulence in the lower portion of the storm -- the part of the hurricane that effects a community -- and eventually work to make buildings safer and less vulnerable to strong winds.
``We're kind of different people. We don't wish bad things on people, but when they happen we want to go out and study them,'' Schroeder said.
Related Links
University of Oklahoma School of Meteorology -- provides information on Doppler on Wheels (DOW)
Science Magazine, April 24, 1998 -- includes an article on DOW by Dr. Joshua Wurman
Texas Tech University Wind Engineering Research Center