Michael Thompson's Australian Storm Chase Diary

Severe isolated storm -Southern Highlands, NSW, 9th March 2000

A small downburst followed by hail was the highlight of the storm, note in the first picture how the cold outflow is being drawn up into the fresh base on the right.

There are some setups that almost guarantee storms, even in a season as poor as the 1999-2000 one. Overnight we had steady rain and wind from a small low pressure system, but this cleared rapidly around 9am as the low moved southwards. As long as the winds do not go offshore or the trough pass to the NE this can be a classic setup. Things weren't to bad in the upper atmosphere as well with a jet stream exit region to the NE, if fact a separate cloud mass could be seen to the north and it was slowly making it's way south, but that was a few hours yet.

I was fortunate enough to be off work, so about 2pm with some congestus over the ranges I set off to Picton. To be honest at this stage I was a little worried as nothing had happened, I took my wife and baby along, if nothing else we could have a drive in the countryside.

Fresh updrafts keep going up on the NW flank.I reached Picton about 3pm and there was a weak cell to the NW, over the lower Blue Mountains, it looked dead and not worth chasing so I bade some time having a cup of tea and looking at shops. When we returned to the car around 4pm things had started to improve, a small tower had gone up about 50 kilometers to the south. I drove to the local lookout and weighted my options. The weak cell to the north looked far better tan it did 30 minutes earlier, but the ones southwards over the southerm highlands looked much stronger..

Over the next half hour the storms to the south merged into a line, from a distance one could be mistaken for thinking of it as a single unit, but as I got closer you could see that where several cells. Fresh updrafts kept building on the rear NW flank, a strong jet was taking the storms SE rather quickly. A lowering on the north flankAt pheasants nest I took a couple of pictures, including a nice lowering. At this stage a severe thunderstorm advice had been posted by the bureau and annouced on radio. A pattern of was setting up where each downdraft would help push up a cell further north than the last, thus the storm line propagated northwards. I continued to the town of Mittagong and at approx. 6pm took the video stills at the top of this story. Not long after these pictures the rain free base to the right let loose with heavy rain and hail which lasted about 15 mins. My four month old baby found the sound of hail on the car's roof quite exciting, a future storm chaser in the making !

This cell was the last for the day, the line had lasted about 2 hours, but suddenly fell apart. The radar loop shows this all too well. Click to animate, thanks to Matt Smith for saving this loop.

Click to animate

Image courtesy of Bureau of Meteorology