Eastern Downs Supercell Chase

January 25, 1999

The model prognosis for the border ranges of SE QLD and NE NSW indicated a good chance of isolated thunderstorms around the vicinity.  With LI’s between –1 and –4, and a 40-60kt jetstream, we were expecting something nice, but nothing like what we experienced!

I awoke at 7am to see the sky 5/8 overcast, with a mixture of medium cumulus, cirrocumulus, stratocumulus, and a tiny patch of altocumulus castellatus.  It was already quite warm and humid, at 8am it was 27C with a DP of 21C.  The sky was looking fairly promising, and I was hoping for something good.  Unfortunately,  what I was afraid would happen came true.  The cloud began to thicken up, by 9:30am the sky was filled with medium cumulus and stratocumulus, certainly not what  we wanted for storms!

Ben and Ross picked me up at 10am, we had decided to head towards Warwick, the satellite pictures and models suggested this would be where most of the  development would occur (within a reasonable chasing distance.)  We had to quickly stop by at Ross’s work, and also purchase some film before we traveled down  to Warwick.  Fortunately, the general trend was clearing as we headed SW, and about 30km from Warwick we observed some rather promising Cb to the WSW.   The AM radio had some very slight static interference, about twice a minute.  We arrived in Warwick just before 1pm; we decided a quick stop in the local library  would be an idea to access the Internet for information.  With a very quick stop for lunch, we decided to head further west, out to near Inglewood to reach the  promising development.  During this period, some congestus started to form to the S, SE and also to the N, and the cells to the west that had already started  precipitating appeared to be weakening out, with any new developing dying as quick as it shot up.

We were about 20km’s out of Warwick when we decided to turn around and head back to warwick.  Unfortunately, we also had to move back under the low cloud, which made observations difficult.  Wondering whether we should try our luck heading south, or head north in the hope that the congestus/TCU would form something nice, we again decided that another visit to the library was necessary.  It was now 3:00pm and we decided that we’d head north, and then cut in west to observe the congestus/TCU development.  By this time, it had formed a small cell, and had begun precipitating, no visible lightning or audible thunder could be heard, however now the AM radio was recording almost continuous static!  Very soon, it began to have an inflow band to the SE, which certainly aroused my curiosity, but I discounted this as anything major as the model prognosis certainly did not indicate any rotational storms.  We drove further west to try and get closer to the storm, where a ragged shelf cloud could be seen.  The rain shafts of this cell began to look very thick and dark, and at this stage it probably contained hail.  Ideally, we wanted to move further north, but there were no sealed roads that went north, unfortunately to follow the road we were on would lead us into core punching, and the unsealed road to the south would be muddy from rain.  We decided to head back east, and travel south back to Warwick and see if we could observe any  interesting features behind it, and follow it north on another road.  The storm was moving very slowly at this stage, so we thought that it shouldn’t move very far.

Unfortunately we ran into rain, and when we arrived in Warwick, it had appeared that they had received some very heavy rain from the fast flowing water in the gutters along side the road, and massive puddles.  We decided one last trip to the library would be necessary, as there was too much cloud to observe anything.  The cell that we had seen previously appeared to have moved very quickly north, which was strange as it originally was moving northeast, like the rest of the storms in the area.  I thought that we should try and head north, towards Toowoomba in the hope that the storm would last, as it certainly appeared to still be strengthening.  Ross  and Ben agreed, and we made a dash north in a last effort to try and observe a decent thunderstorm (although the visible features on this storm were already quite good!) From behind, the thunderstorm still had very thick and solid rain and hail shafts, but structurally, there was nothing extraordinary about it.  Although the small section of the anvil that could be seen was very thick, and fairly crisp.  Unfortunately, we could not tell how high the storm was, but I estimated it to be near 12,000m.  We couldn’t see the base very clearly, because of trees and hills. However, I observed a cloud lowering at the rear of the cell, which kept me wondering.  But I only saw  it for five seconds before it went out of sight again for at least ten minutes; which by then had completely disappeared.  At about 5:15pm, it appeared that the storm had weakened a little, as the anvil appeared to have lost some of its formation, and the general storm looked a little less organised.  We could clearly see the cells about 100km SW of us, which were looking very nice, and even had an overshoot on them.  It was then that I thought maybe we had made the wrong decision, but we continued to chase this other cell, as by now we were well over an hour from any other storm activity.  Not to mention, the old ‘gut’ was saying that something was ‘special’ about this thunderstorm.

As we finally neared the storm cell, it became apparent that the cell had a very strong guster, with the rain shafts at a 45-degree angle at times!  As we continued to move WNW, we saw what appeared to be a rain free base, then as more and more of it was revealed, it began to look circular, it was rather low, and it had inflow bands from the SW and the NE!  Suddenly we realised it was fully rotating, we could not believe our luck!  In a desperate effort to avoid the rain, we drove towards it for 1km, before driving parallel with it heading NNW on a small road.  At this stage, we weren’t too sure where we were actually heading, we had only one intention, to follow this storm cell for as long as possible!  It was difficult to try and keep out of the rain, while also staying well clear of the rain free, rotating base.  We certainly did not want to core punch this beast, and we only wanted to observe a tornado, not be in one!  I had never seen a storm rotate like this before, the inflow bands were so long! Not to mention it was visibly rotating (slowly, but none-the-less, rotating!)  There was lightning every few seconds on average, the rain shaft hid most and you could  only see a flash, but there were a few CG’s that were observed.  Although we did not see many of them, the ones that we did see were huge, the bolt was  tremendously thick!

Watching the base continue to rotate, I was praying for a funnel cloud to appear, at about 6:45pm what appeared to be some lower scud began to form very quickly, within one minute there was a full wall cloud!  (I believe that my heart was beating over 400 times a minute at this time, it was astonishing at how quickly it formed!).  Soon, a small inflow band on the wall cloud formed, I was dying in suspense, I wanted a funnel to form, unfortunately, it wasn’t to be. But it was so close, that if  some one under the base would have sneezed, one would have formed! (Metaphorically of course, but it was extremely close!)

By 7pm it began to get dark, and we were running out of sealed roads to the north, we pondered staying put and waiting for the storm to pass, but decided to make a dash east to avoid getting caught up in the core of the storm.  The storm continued to move NNW, but because of the lack of daylight, and also because the rain curtain had now obscured most of the lightning, we decided to head back home.  While heading back to Brisbane, we noticed the occasional flash of lightning to the south, we didn’t see much, but then again one cannot be greedy!

I myself originally thought that some people went over the top with storm chasing for so long, and also for hundreds of kilometres.  I ate my own words (along with Ben) as we traveled 650km and we were on the road for just over eleven hours!  But worth every second of it with a wonderful reward!

I personally believe that this particular thunderstorm was indeed a supercell, here are the notes that certainly support and are partly indicative of a supercellular  thunderstorm:

The storm lasted for well over four hours, in fact, at 10pm there was still lightning in the area.  Although it may have been a different storm, this would be unlikely as there was no other promising development.  If this was the same storm,it would mean this cell lasted over seven hours!

It had a sustained rotating updraft – the rotating updraft was visible for approximately forty-five minutes.  Earlier in the afternoon, there were also inflow bands (which suggest rotation) which would mean over four hours of rotation!

The cell was originally moving NE, then N, then it headed NNW!  All of the other storms were moving NE or ENE.

The only data on this storm that I have is that 50mm of rain was recorded at Oakey from this storm.