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The Brisbane Tornadic Supercell: Tuesday 13th October 1998
by Anthony Cornelius

On Monday, the day before the storms, I was actually concerned about the amount of moisture in the air – or rather, lack of. At 4pm Monday, the DP was 11C – which was certainly lower then desired, as SE Queensland thunderstorms generally require high DP’s for severe thunderstorms. But at 5pm, not only did the hydrometer in my house climb, but the Brisbane airport observations showed the DP was 18C! Also the trough was expected in the afternoon, which was music to my ears as the many of the previous troughs in the past month had only brought with it a few showers and light storm activity on the ranges. Both of these immediately made me feel much better. A friend of mine also reported that he spotted some altocumulus castellatus in the afternoon – another very promising sign!

The morning commenced very warm, and muggy – altocumulus castellatus was already covering the sky by 10am. This was when I began to get a gut instinct that something "big" was going to happen – although the models already hinted at it! At around 10:20am, I could see some Cb to the distance, but I was actually down on a field at that time, so it was very difficult to tell the structure. During the day, it was very difficult to observe the clouds, as I kept moving from class to class, and generally I didn’t have a good view, what made it worse was the sky was partly obscured with other clouds. For this reason I was generally left guessing what was happening However when I walked out of my chemistry class, I immediately knew that this storm was severe. I saw a very well defined flanking line, and a beautiful crisp, back-shearing anvil. The storm that I saw was actually the storm that had just recently devastated the township of Warwick at about 11:30am. Certainly unusual to have a severe storm in the morning! The "Warwick storm cell" actually moved to the south of us. Fortunately in my next class I was able to grab a window seat, and I sat staring out the window watching the many CG’s. Initially I thought it was one large cell, but soon I saw that there was another cell – that cell was the one heading in my direction! I observed a shelf cloud and a lowered base on the cell that went south of me. The first cell appeared as dark blue, with a "saucer-plate like anvil" (similar to that of rings on a tree, each ring indicates a new period of life, just as the ring on an anvil indicates a new stage;) indicating long life. I could not get a very clear look at the lowered base, as the contrast was low with the rain shaft covering part of the lowered base. I did see a few clouds below the lowered base, but they looked more like scud clouds then anything else. There were no damage paths from that cell, or any funnel sightings so it would be quite plausible to say no tornadoes occurred from this particular cell. At around dismissal (3:05pm) I could see the cell that hit the city developing – it had either developed very quickly, or traveled very quickly, as there were no visible signs of its development previously. I assumed that the cell had just traveled exceptionally quickly, as most of the sky to the S and SW was covered by the two other cells. I later found out that the cell had developed very quickly in the conditionally unstable atmosphere. The cell heading in our direction again had a very crisp anvil, but in some areas it was slightly weaker and more fibrous, however this could have been older "waste cirrus" from previous storms. This cell had to have moved very quickly, as our bus was traveling in an easterly direction on a road at approximately 60km/h. Yet the storm caught up with us very quickly after turning south! At around the Carina/Camp Hill area I saw an awesome shelf cloud, and then to top it off, a CG went straight through it! It was very exhilarating and certainly very, very exciting.. Whilst traveling south, I had a good view of the side of the cell that was heading for the city. It had a "textbook perfect structure" with an extremely well defined anvil and structure to the side. The way that it "jutted out" was simply incredible. However soon we were hit by our gust front from the cell traveling towards us. We punched, or if not we were very close to punching the core. Although the core area from this storm was indeed covering a very wide area! We experienced pea sized hail, extremely heavy rain and very strong winds, I had originally thought them to be around B10 (Beautfort Scale Force 10) – but in hindsight, the branches down didn’t indicate B10 in the immediate area I was in, I would have to say certainly B9 at least though, as the bus was getting buffeted by winds and there were many small and medium branches broken off. I watched in amusement as many cars began to drive up onto the footpath and park underneath the shop awnings! I didn’t blame them though, although at this time hail was only between pea sized hail and 2cm hail – the winds made the hail act like sandpaper, literally just tearing leaves off trees. Visibility was almost nil, I was actually concerned that we might have an accident, fortunately nothing like that occurred! Two minutes later we arrived at Carindale Bus Terminus – Carindale St was already flooded with water (not from a local creek, rather storm water drains full) Our bus pulled up at around 30-40km/h and produced a wave about 5 foot high from water, so that might give you an indication of how much rain had come down! As I walked out of the bus, the wind almost blew me over, it just hit you like a wall! And the rain and hail was stinging on my legs, there was an eerie "mist" analogous to that of a waterfall as the water hits the water below. It was truly an awesome site! In about four or five minutes, the water began to "backwash" through the storm water drains, as a storm water drain about 6 inches higher then the road, which was not getting any rain in it as it was well undercover began to bubble up water!!! The terminus roof was deafening as part of it was corrugated iron, I had to yell to communicate with a friend. One interesting note about the storm was that towards the end, winds very quickly turned gust B6/B7 and from the north. I am still at a loss to why this occurred. One of my thoughts was that the trough hadn’t moved through yet, which was true the wind change did not occur until later on that night. But I thought it was certainly weird that winds should suddenly change to the north, as I’ve never experienced a storm with such a gusty and strong north’ly wind towards the end of it.

The heavy rain, hail and strong winds subsided in approximately ten minutes. Not surprisingly, my transfer bus was 25 minutes late! As we were traveling along, the streets were littered with debris from fallen branches, twigs and leaves. There was also little "hail patches" on lawns around the streets. Our local creek "Bulimba creek" had risen between four and six feet flooding some areas of our local park and some of the flood plains on the horse fields nearby. I also later found out that the "Clem Jones Centre" – about 1.5km away from Carindale Bus Terminus lost its roof, it was taken over 100 metres across a football field and slammed into power lines on Stanley Street. It was a miracle that no one was tangled in power lines on Stanley St considering that it is one of the main roads that lead onto the freeway. It’s highly unlikely that this damage occurred from a tornado, as there was no damage path. Also, the thunderstorm that hit my area only exhibited a "bow echo," and not the ominous "hook echo." Although "bow echo" storms, otherwise known as downburst storms can produce tornadoes, they are generally not common and weak. It is more likely that the winds from the severe gust front damaged the building.

When I got home, there were no visible signs of damage, until I opened the door. I immediately thought it was strange when water fell from the top ledge of the door as I opened it. Just to the right of our entry is our dining room, the dining room light fitting was hanging from the cord off the ceiling. I immediately thought that perhaps lightning had hit the house and that it blew out the lights, but everything else was still working. As I walked underneath the light I noticed that the carpets were soaked. What had happened is that the strong winds and hail had stripped some of the leaves off our trees and the winds carried them into our gutters. The gutters immediately got blocked and water fell into the roof. It then came out through our dining room light fitting and also drenching some of our carpets. After I saw this I rang my parents to tell them about it. I then checked the rain gauge – 35mm(!!!) However with some moderate rain after the most intense rainfall, I estimate about 25-30mm at least in 10 minutes. That is between 150-180mm an hour!!!

Unfortunately I didn’t have my camera with me, all I was able to do was take some pictures of the back part of the storm. But there wasn’t much to look at except for the flanking line.

Soon damage reports on the news started to come in, the Fortitude Valley and Kangaroo Point regions were hardest hit by the other cell. Then Bowen Hills, Newstead, Breakfast Creek, Hendra, Alboin, Clayfield – even Beenleigh had some damage reports by another cell. Over 50,000 homes lost power, the SES communications tower was knocked out by the storm, trains were stopped as trees were tangled in some power lines. Within minutes what was originally a "smooth run out of the city" became a chaotic, traffic gridlock as lights were out in many places and debris from roofs littered some of the main roads. That evening a plethora of damage reports flooded in, but the news had some very interesting footage. That footage was of swirling and rising debris, and also what could have been a possible funnel cloud in the top part of the footage. There were many eyewitness reports of "everything was flying around – sheets of iron came flying like missiles;" "All of a sudden it became very black – then this wind came, it was like a nightmare. Lightning hit the tree across the road and hit another tree and cut it in half then all the staff were out the back…it was like the movie Twister." There were reports of shop windows being "blown out," certainly indicative of a tornado. Perhaps another interesting note is that the damage was generally localised in one line. The worse damage was at Fortitude Valley and Kangaroo Point, these two areas are only separated by the Brisbane River. Many units lost their roofs, many trees were down and many fell on power lines.

There is still some debate over whether or not it was actually a tornado, but there is significant evidence to support it. First there is the footage swirling debris rising with what appears to be a funnel cloud above it. Although the condensation funnel did not reach the ground; by definition a tornado’s condensation funnel does not have to reach the ground. Another note in the footage was that the storm was a HP supercell (high precipitation), yet in the footage of the rising, swirling debris there was little rain present. This would indicate that the footage taken was at the rear-end of the storm. Most tornadoes in a mesocyclonic supercell form at the rear end of the storm. Which raises yet another piece of evidence; the storm struck the city at 3:40pm, this was when the damage was the most severe. At 3:40pm the radar pictures show a hook echo present. A hook echo indicates the presence of a mesocyclone. Although not all tornadoes are formed from a mesocyclone, most are.

By viewing the damage shown on the news, there were many units that lost their entire roof. This would indicate F2 damage, but the roofs were flat. As a general rule, it is much easier for tornadoes to tear off flat roofs then sloped roofs. However a F0 rating would certainly be an underestimate of the damage. It is for these reasons that I believe that the tornado was an upper F1, as the damage caused was more severe then a F0 and there were no indications of F2 damage. One interesting note is that there was an unconfirmed report of a "portable office going airborne." This is analogous to mobile homes being torn apart or carried for a very long distance. Which is only worth an F1 rating.

Warwick was also hit badly earlier on that day at around 11:30 am, many trees were uprooted and over 50 houses were un-roofed. Many students at schools had to take cover as windows were smashed by winds in excess of 90km/h. Other reports of trees falling on caravans, garden sheds being blown away, flash flooding and loss of power also came in. It was rare that a severe thunderstorm would occur in the morning, especially with such intensity. Yet for some unknown reasons, from my knowledge severe thunderstorm warnings were not placed until 2pm!

There were also unconfirmed reports of brick-sized hail. However sometimes eyewitnesses tend to exaggerate their reports. But a friend of mine in a nearby area to where the brick-sized hail was reported informed me that they received fist-sized hail that actually destroyed their guttering!

The total damage bill of this thunderstorm was estimated at a staggering thirty-five million dollars. It was described as Brisbane’s worst thunderstorm since the 1980’s. I believe that it was somewhat similar to the 1989 thunderstorm on Christmas eve, as it too was a HP supercell. But this time at least 15 individual cells formed throughout SE Queensland, three of which were confirmed supercells. And many of the others were severe multicells. It was a rare event to have such a line of severe multicells mixed with three supercells, as often supercells form where there aren’t many other cells nearby. Although these cells caused damage, destruction and chaos in Brisbane, it was certainly by no means equal to the great 1985 Brisbane storm. One positive benefit of these storms is that there are now requests to have Brisbane "cyclone rated." This will help eliminate further damage in future years to come. But it is no doubt that Brisbane will eventually get struck by a storm worse then the 1985 storms, it’s just a matter of waiting.

Document: 9810-01.htm
Updated: 14th January, 2003
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