Transcript from Sub-VORTEX Interview
with Erik Rasmussen and Josh Wurman

[Erik Rasmussen]
I'm Erik Rasmussen from the National Severe Storms Laboratory. This has been informally dubbed "Sub-VORTEX", and that's just kind of a funny name because it's like VORTEX but a little bit of a smaller experiment I guess. Our objectives are pretty much the same as VORTEX, only more focused this time.

We learned some things in VORTEX, I think, about tornado formation. Uh, one of the things we learned, for example, is that we probably don't need to collect data throughout a whole supercell. It seems like all the important things for tornado formation are going on in an area that's just a few miles across. So we can attack that area with a lot fewer vehicles and sensors and with the dual-Doppler radars and learn what we need to know. The field coordination vehicle, I'll be in charge of, and then we have the two Doppler radars operated by Dr. Josh Wurman, and his colleagues and students from the University of Oklahoma.

[Josh Wurman]
"Josh Wurman, I'm a professor at the University of Oklahoma. The truck here is one of the, uh, Doppler-on-Wheels, mobile Doppler radar. Uh, you're looking at the DOW 2. And we also have the DOW 3, which is another system very similar to this one that has characteristics very similar to a Weather Service radar, um, but it's on wheels so we can actually get up very close to storms as opposed to waiting for a storm to come to us, which would be a very rare event. Um, so instead of a sending mountains-to-Mohammed method we're actually taking Mohammed to the mountain and getting very high-resolution data.

What we're trying to do with the two radar trucks is place them so they have different views of the same tornado. As Erik was explaining with the dual-Doppler deployment scenario you try to get the radars so they're approximately looking at 90-degree angles to the same tornado. Um, so the one radar might be out ahead of the tornado but along its path and the other one might be behind the radar along its path. Or potentially we could even deploy one tornado – or one radar south of the tornado and another one north of the tornado and have the tornado go between the two radars, but that's a more difficult thing to do. Um, but the idea is to get them as close as we can, reasonably safely. Uh, and also as close as we can to get data for a significant period of time on a moving target, which typically means probably two or three miles away from the tornado, either along its path or on either side of the tornado's path.

[Erik Rasmussen]
When we have a forecast that supercells are possible in a given area, say, within several hundred miles, we will all get together at the Severe Storms Lab and depart probably in the late morning and travel in a caravan to the, uh, area where the storms are expected. Then once storms begin to develop we will move towards the location of a storm and just begin monitoring it. For example Josh can actually scan the storms with his Doppler radar as he rolls down the road, and inform the rest of the participants of where the storm is and how it's moving and that sort of thing. Then once you have an indication that the thunderstorm is turning into a supercell then we'll begin collecting data.

We'll maneuver the radars along side the storm and begin scanning it. We'll take our mobile mesonets and start moving them back and forth underneath the backside of the updraft to watch for the formation of the rear-flank downdraft. Up to this point we really don't know what gets the tornado to the ground. It seems from some of our VORTEX findings that this downdraft may be transporting the storm's larger scale rotation to the ground in one way or another and then focusing it into a small location, causing the formation of the tornado.

Then once we collect all the data in this experiment it's going to be fairly straightforward to analyze because we had the experience of VORTEX with collecting the same sorts of data sets before, and we know how to analyze them and integrate them together to, uh, look for the clues we're after. And I think once we collect the data in Sub-VORTEX they'll be some questions we can answer in a matter of months, uh, regarding tornado formation.

Updated May 2001