June 6TH Chase By Robert Prentice And Friends

Dave Gold (TX A&M), Bill Gargan (OU) and I (NWS) chased together June 5-8, 1993. On the afternoon of June 6th, we met up with an IMAX film crew consisting of one (1) camera man at Goodland, KS. Thus began an interesting two-day chase with IMAX.

Good chase weather was expected. A powerfull, late-spring storm system was forecasted to eject into the northern plains on June 7th. We thought June 6th would be "The day before the big day" (which is often/usually the best day to CHASE!). Dave and I decided to chase the dryline/warm front intersection over southwest NE that we observed on the Goodland WSR-88D. As it turned out, we should have chased further east along the warm front since we missed the slow-moving, mega-tornadic supercell at sunset near Elm Creek, NE! We were happy with with what we saw anyway.

We chased (from the southeast side) a picturesque supercell along a slow-moving warm front (~70 dew points!) between Indianola and Stockville, NE. Our storm was moving due north at a pretty good pace (possible left-split?) and we did not stop to film. We drove for what seemed like an eternity on the back dirt roads (not good!) and almost got lost taking the wrong fork in the road due to incomplete AAA & Rand McNaly road maps (I suggest buying the individual county road maps for NE from the Transportation Dept.). We finally hit pavement near Stockville and whom do we see? Greg Stumpf, taking time-off from a research project to chase out of CO!

Dave and Bill were dead-set on seeing a tornado before sunset through the warm front, 70 dew pt haze...so the IMAX camera man and I stopped to film. It took him about 5 minutes to set up, and when he finally did, a stratus inflow band passed over to block our view! He might have gotten lucky if he filmed while the stratus inflow band passed over-head. That would have been an awsome piece of IMAX film...a stout updraft w/backsheared anvil, orangish sunset lighting, and black stratus riding the inflow jet, feeding into the updraft. However, I do not know if this film turned out.

On June 7th we chased out of Grand Island, NE into SD and MN. We fully expected a tornado outbreak across the northern low plains, but exactly where to chase was the question. Dave wanted to stay further south over NE/IA, but I was worried about the strong cap along the dryline/cold front. I thought our best bet was near the triple-point further north in eastern SD. After a few hours of "north!" "north!" we wound up SD.

Radio reports of a damaging tornado west of Sioux Falls were broadcasted, so we plotted an intercept course north of Sioux Falls. On I-29, we passed a well-defined E-W oriented stratus band, denoting the warm front. The 21z (4 pm) Sioux Falls ob (immediately north of the warm front) was 77 temp, 71 dew pt, with ESE wind 20g29 kts. We kept straining our eyes in- between the gently-rolling hills of the "corn-belt" horizon, looking for any signs an updraft base or tornado. Then suddenly we had a view and saw "it" along the western horizon. A giant, "mile and a half" wide wedge tornado that was twice as wide as it was tall (below cloud base). We took the first available exit and I began to film the beast on the horizon, several miles to our west.

I turned to the IMAX camera man and asked if he could set up. It was an awsome spectacle to be in the channeled inflow (40-50 kt) of what was later verified as a violent (F4/5) wedge tornado. He just meekly/sadely chucked since it was too windy (?), the wedge was too far away and moving too quickly to flim properly. The storm was moving NNE at 55 mph(!) (I measured this based on Huron WSR-57 observations), and we had trouble keeping up with it even on the interstate! The wedge was in it shirking stage when we first saw it and a new tornado quickly touched down. The new tornado "roped-out" near Coleman, SD just before crossing I-29. Our entire tornado view lasted 13 minutes.

So, to answer one of your questions...IMAX saw more than one tornado during its trips to the Great Plains. In fact, they saw a true wedge! FILMING the tornadoes however, turned out to be a great challege!

I have not seen the IMAX film on storm chasers, but listening to the reviews I get the idea they did not focus on breath-taking panoramic views. Is this true? To me, the IMAX format was INVENTED to showcase PANORAMIC views of storm structure, including all sounds that go with it (wind, thunder, birds chirping, etc). Tornadoes are great(!), but they are not the end-all-beat-all of storm chasing.

Chasers who are only interested in seeing up-close tornadoes are eventually going to get burned-out and/or give up chasing. I get great pleasure and satisfaction from the other aspects of chasing such as:

1. The chase forecast

- A HIGHLY speciallized skill, (quite unlike general severe forecasting)
where you try to guess (sometimes down to the scale of a small town!)
exactly where the most awsome, pictureque, isolated, tornadic supercell will
be

2. In-the-field storm positioning

- Requires a great understanding of storm environment/structure/dynamics,

topography, cartography, etc....where to "best" view the "best" storm

3. Photography (video and 35 mm)

- Knowlege of lighting, filters, foregrounds, framing, composition, etc

4. The "Route 66" experience

- The fun and adventure associated with your storm quest

5. Meeting other storm chasers

- Swaping storm tales at at the NWS office or meeting at a lonely intersection

6. The ambiance of witnessing storms on the Great Plains

- Probably impossible (and too personal) to explain

"Your personal guide to convective nirvana"

Robert A. Prentice, MET Instructor
Norman, OK
RPrentice@NEXRAD.OSF.UOKNOR.EDU