Monday 8th of October 2007

Chase Report

On this day a trough triggered thunderstorms from Western QLD to North East NSW. After a good lightshow the night before, I decided to chase in the area southwest of Brisbane. The previous day large storms had formed in this area, and the forecasts and models were quite similiar. GFS showed strong instability and good moisture inland in the Lockyer Valley. I arrive just south of Ipswich around 1pm and waited for the first development to begin. All the way there I'd been seeing strong updrafts go up, then dry out. There was no organisation or structure to it at all, and no precipitation visible.

After a while I decided to head further south towards Boonah. A report from Julian Ripamonti indicated some better organisation down that way. About 10km north of Boonah at 2pm, I stopped to watch the cells to the north. They seemed to be getting going better near Highvale. While watching this an updraft to my west really intensified, then anvilled out. I started hearing some rumbles from this cell. To the south large cells were visible around the Kyogle and Lismore areas. The cell to my west continued to intensify and was soon dropping some rain. It seemed to be heading south of me. I decided to head to Boonah.

On the way into Boonah I passed under the rainfree base of the cell. There was interesting wedge shaped formation of cloud under the base. I was thinking about heading after it to try and get ahead, but I decided there was no way I could catch it on the way to the Gold Coast. I joined Julian at the lookout at Boonah. By the time we arrived there, the updraft on the cell that had passed over us was exploding upward, while being pushed over by the shear. It had an angled updraft. At times it looked to be visibly rotating, but only for about 10 minutes at most. Successive flanking towers seemed to go up, then get pushed horizontal near the top, and go into the anvil. It also got a solid precipitation curtain underneath it. The cells west of us appeared to be rather dry and dying, so we decided to follow the cell with the massive updrafts to Beaudesert.

By the time we arrived there around 3:30pm the cell was visibly weakening. The updraft had gone very whispy. The cells to the west seemed to be trying to do something on radar, but it didn't look all that good. There was a cell, red on radar, heading for Archerfield, which I decided to try to get in front of that. I headed up the Mount Lindsay highway, finally stopping just north of the Logan Motorway. At this point all I could see was a curtain of grey. I was starting to get some light anvil rain, but on radar and visually it looked like everything was dying. I decided to head home via the Logan and Gateway Motorways.

As I headed over the Gateway Bridge, I saw a solid wall of updraft to the SW. The cells had reintensified and reorganised. A check of radar indicated a line angled from NE to SW moving through from Ipswich. It looked like it would go just south of the CBD and head through between Archerfield and Greenbank. I decided to find a vantage point near the city, and get some shots just north of it. At this time I also noticed the beautiful cell on the border. It had a very big round curved anvil structure and was being illuminated by the sun. I arrived on Bowen Terrace above the Storey Bridge at 5pm. At first all I could see was the anvil of the border cell, and the anvil of the line that came from the Ipswich area. It looked like it would pass just south of the city, so I figured I was in an ideal place to see it as it passed over.

By this time another larger line, stretching SE to NW was forming in the Lockyer valley and moving rapidly NE. The small line died as it passed over me, producing very little lightning and a bit of light rain. It was hard to see where that cell ended and the big line started. As it got darker around 5:30 precipitation shafts became visible to the south and there were flashes and rumbles behind the city. Soon CG's were dropping everywhere around the city, which I took photos of. There were some spectacular strikes. There were other strikes southeast of Woolangabba and some to the west as well which I wasn't quite able to see. I concentrated on the best view looking across the bridge and the city. After a while anvil rain started, so I used an umbrella to protect the camera for a while. Unfortunately though some of the best strike photos were affected by rain on the lens and some focusing errors I made. Nevermind, I'll do better next time.

At 6:10 a rush of outflow hit and inverted my umbrella. Winds were around 40-50km/h. This made it impossible to take pictures without the camera getting wet, so I ran for the 4wd. Around this time there were many close strikes in city, with thunder echoing and booming around the place. I decided after a while to head for Redcliffe, to get pictures of the lightning as the line moved out to sea. I arrived at Scarborough at about 7:10 and took photos for the next half an hour. There were 4 distinct cells that were producing lightning, mostly embedded in the rain curtains, but some were clear and visible. Some of the best strikes were over Moreton Island. At 7:45 I decided to call it a night and head for home. If this is a preview of what this season will be like, I think we're in for a good one.

Lots more pics in the Photo Gallery for this chase!