Monday 26th of December 2005

Chase Report

Today had an interesting setup, with a long confluence line crossing through the south east corner near Toowoomba and quite good instability and moisture. However there was quite a strong cap in place and this halted development until later in the afternoon. The best convergence was to the south near Gatton early in the morning, with higher instability to the north in the Sunshine Coast hinterland. I chose to go for the best convergence, because that often produces the best action.

I departed Redcliffe at 11:30am, heading for the best confluence line area, a triple-point near Gatton. After lunch I arrived in the Laidley area around about 1pm. Travelling along from Rosewood though to Laidley, I eventually stopped at a dam near Laidley. Watching from here it was obvious that the cap was quite strong. Towering cumulus clouds were going up in a line stretching from the south to the north-west of my location. There were three main areas of activity, each becoming active then stopping when it hit the cap. I waited here for around an hour, hoping the cap would break and something would get going. There appeared to be a reasonable cell to the northwest, but that was quite distant and also dying. All the activity occured along the confluence line. After a while the activity to the west got going again and I decided to move out to Toowoomba.

By the time I reached Picnic Point at Toowoomba, most of the cells over the Gatton and Laidley area's had died. It almost looked like they had dried out, but the dew point temperatures were still quite high. There was very little convection in the area, except to the northwest with a small cell starting to look good. I received a radar report of a large cell near Yarraman. So after a quick fuel stop I decided to head for it, travelling up the New England Highway. On the way I stopped just north of Toowoomba in a town called Hampton. A cell to my west had started to produce anvil rain and was looking fairly reasonable. No lightning was visible while I was watching, but there was a lot of noise on the AM radio. The activity to the north was looking very good however, so I decided to continue on and go after that. By now a very good looking anvil was visible with strong updrafts and a pileus cap.

The forecast I did before leaving indicated that the steering winds would be mostly easterly so I was expecting the storm to move east. When I reached Crow's Nest it indeed appeared to be visually moving east. So I took a turn off in Crow's Nest that was a more direct route to Blackbutt, hoping that it would get me closer to the cell. This turned out to be quite a good choice. Although the road was gravel in places, and quite hairy with other cars coming around corners at 80kph on the wrong side, it provided excellent views. It wouldn't be a good choice in the wet however, I imagine the red dirt would get quite muddy. Strong updrafts continued to appear to my north, with the appearance of a flanking line extending eastwards coming into the cell. Other cells behind be continued to form as well.

From Googa, near the Mt Binga location on the 128k Radar Loop, the cell became very impressive. There was a rainbow, with the updraft curving up over it. It appeared to be quite a large cell, it actually turned out the be a splitting cell, with one cell moving to the east and eventually dying, while the other moved north. I didn't fully understand this until I got later radar reports. I still didn't see any lightning, but there was a brightly lit precipitation cascade to the east. There was a lot of radio noise too. When I reached Blackbutt the updraft on the east moving cell seemed to be quite a distance from my location. So I headed down to Kilcoy. I would have liked to have follow the north moving cells, but personal committments required me to be home in the early evening. Once down off the range, I stopped in Moore to get some shots of the updraft towering overhead, still with a rainbow. I also noticed the cells behind me had continued to develop and were now looking quite impressive. One was near Crow's Nest, and the other was the rest of the split cell going north.

Arriving in Kilcoy I stopped on the main road to get a good view of the cells to the west. The eastward moving cell had all but died, so the only good activity was behind me. The cell near Crow's Nest had become quite large and was still stationary. The other cell was moving north, and still had an impressive anvil structure. Not much detail was visible however. The Crow's Nest cell eventually started to move north as well. Either I got the steering winds wrong on my forecast, or the cells were propagating along the confluence line. After watching for a while I decided to head for home, hoping to get the chance to stop along the way to get some sunset pictures with the two cells. Unfortunately low cloud prevented this.

Overall it was a great day, with a slow start. Hopefully some of the other chasers were able to follow the northbound storms. They looked quite severe so there should be some good shots coming from there. I think it was a reasonable choice to head to Gatton at first, but maybe I should have left there a bit earlier when the cap wasn't breaking.