5/27/97: Jarrell, TX F5

[Darrin Rasberry]

Opening up a can of meteorological worms with this one. The cell moved southwest, producing a huge F5 tornado that obliterated the town of Jarrell, Texas. The radar grab can be seen here: http://www.youtube.com/watch?v=92DadB6ZnbE

I would be interested to hear from people chasing that day, and from people who have opinions on the odd storm motion the supe took.

[Chris Lott]

Lon Curtis, a meteorologist in Waco chased that day. Here is his log.


http://www.stormtrack.org/library/logs/chase116.html

[shane turner]

In my opinion this is one of the few tornadoes that created damage that was beyond my imagination. The other two tornadoes were Harper, Kansas May 12, 2004 and Hitchcock/Red Willow, Nebraska June 15, 1990.

[Greg Blumberg]

I don't have any real scientific data, actual chase account or anything of that sort, but I can recall a personal account of traveling up through central Texas on that day. We would often take a spring trip up to Ft Worth to visit family. I believe our route would be to take some highway up from Houston to get to I-35. Usually our spring trips would be be filled with us driving through spring storms and getting some pea sized hail knocking on our car.

On this instance we were either in Jarrell or within the path of the supercell that did hit it, stopped at a McDonalds. My dad asked my sisters and I if we wanted to play at the play-place for fifteen minutes or if we wanted to leave. We chose to leave.

Our trip up I-35, a few minutes after we left, my mother mentioned how much the storm outside looked like it had "tornado clouds." Both she and my father had both grown up in North TX. They were not sure what to call it.

When we reached Ft. Worth, we found my grandmother sitting at the TV with the Jarrell tornado out and saw the destruction of the town we went through. We missed the event by about fifteen minutes. I felt pretty disappointed since I, being 8 at the time and already interested in weather, missed seeing that tornado. It was my final push at being interested in weather, and I vowed that I would see a tornado someday (mission accomplished.)

In the past few years I began to realize the significance of that event and did a lot of research on what happened that day. I just don't remember where exactly I was that day.

Here's a couple of the links to sites that I've found:

SPC's page on the event: http://www.spc.noaa.gov/coolimg/jarrell/index.html

Data filled analysis page: http://homepages.vvm.com/~curtis/Jarrell/Jarrell.htm

SPC Paper: http://www.spc.noaa.gov/publications/corfidi/jarrell.htm

[Jason Harris]

So was there some sort of eventual consensus on the SW movement being from this gravity wave?

--
in addition to producing a series of strong mesohighs, the MCS generated a well-defined gravity wave that propagated southwest across the eastern half of Texas beginning around dawn on the 27th. The progress of the wave could be readily tracked via satellite as the capped mixed-layer cloudiness east of the dry line alternatingly thickened and thinned upon passage of the wave (not shown). The leading edge of the wave is depicted by a wavy line in the hourly surface charts.
from:
http://www.spc.noaa.gov/publications/corfidi/jarrell.htm

And does this conclusion also suggest that the gravity wave might have been partly responsible for the intensification up to F5, as well as a vote for super instability beats out mild shear?
Given the fortuitous nature of the factors involved and, especially, the presence of an MCS-induced gravity wave, it is safe to say that another event of the same magnitude is not likely to occur for some time to come. It is, however, worth noting that meso-alpha scale environments similar to those that were present over central Texas on 27 May 1997 (slowly-moving boundary with weak shear, a strong cap and substantial potential instability) do occur with some regularity over the southern Plains, especially during late spring. For example, such a set-up, minus a gravity wave, yielded an F3 tornado over Lake Whitney, TX (approximately 30 miles northwest of Waco) on 12 May 2000. The central Texas tornadoes of 27 May 1997 serve as a reminder that there exist "unconventional" routes by which supercellular convection may be realized. These events can be problematic from a forecast perspective as they occur well beyond the more-commonly visited parts of severe weather parameter space. Clearly, even in the presence of weak shear, environments that foster strongly-deviant storm motions (see, for example, Johnson 2002) should be closely monitored for the potential of sustained, rotating convection when thermodynamic conditions are favorable for intense updrafts.



I remember seeing the newspapers covering this tornado, and how incredibly powerful that thing was (reading about not just the asphalt but the plumbing pulled out of the ground), and the notable contrast with the little rope that started things off in one of the youtube archived news reports:
http://www.youtube.com/watch?v=YLL8o-urKZ0&feature=related
Note that Lon Curtis's account includes this commentary:
Later surveys and
interviews with residents show that the "pencil' likely dissipated as
the multi-vortex tornado formed (tornado #6).


How's this for a stark image:
http://www.rogersadler.com/Jarrell_tornado/pages/pole_mattress_spings.htm

[Scott Overpeck]

So was there some sort of eventual consensus on the SW movement being from this gravity wave?
--
from:
http://www.spc.noaa.gov/publications/corfidi/jarrell.htm

And does this conclusion also suggest that the gravity wave might have been partly responsible for the intensification up to F5, as well as a vote for super instability beats out mild shear?


For me, this was the one chase that got away from me. I had just moved to Waco to live with my brother temporarily while transitioning from undergraduate studies a Creighton to graduate studies at Texas A&M. I hadn't seen a weather map in like 2 weeks. I remember NWS FWD doing a special weather statement alluding to severe weather potential. I remember seeing the updraft go up like a bomb. My brother worked in Hewitt at the time and told me about the funnels in the area. I wanted to chase, but was by myself. I had no data at all, and didn't like chasing blind, not knowing what I was up against. My brother didn't have internet access at his house yet. In 1997, chasing with a laptop and internet was just catching on and it was dial up at 14.4k or 9600 at best. On ya, you had to either stop at a truck stop to plug into a phone line or have enough cell minutes to dial through your bag phone. Regrettably, I stayed put and watched the storm go off from a distance. In hind sight, all I had to do was drive down I-35 and I would have seen like 4 tors that day. Oh well. Since then I've had plenty of other should've chased days. Live to chase another day I guess.

To answer the questions above - I think Lon Curtis and Al Moller's write up sums up what I think about the event. I think the SW movement was more due to perturbation pressure forces on the sw flank of the initial updraft as well as convergence along the boundary. Kind of the path of least resistance. If anything, the gravity wave played a role in initiation of the convection or a least weakening the cap. Those are hard to prove. I do not think the gravity wave had anything to do with tornadogenesis.

I think in this case the extreme instability - observed 6000-7000 j/kg and I think even a TAMU sounding in the area showed as much as 9000 j/kg, but could be wrong - played a major role. The intense updraft resulting from the release of that much instability used what enhanced helicity there was near the boundary to gain low level rotation. From looking at some of the sfc maps it looked like from some of the obs there were winds with a more easterly component. I just think you probably had some wound up low level hodographs near the boundary which the storm was able to locally enhance and take advantage of. Since then there have been many documented cases of tornadic storms moving along or across boundaries. This case was just a freak case mainly because the environmental shear was weak at best. I suspect that locally along the boundary the shear, or at least low level turning of winds with height, was enhanced for the storm to gain rotation. I could be wrong, but IMO, this is again just another case where a boundary in the presence of extreme instability made all the difference in storm behavior and tornadoes on that day.