Michael Thompson's Australian Storm Chase Diary
22nd January 2005 - Hailstorm - Southern Highlands, NSW

A large circular anvil with a strange collar suggests an explosive updraft.	Hail to 4cm

Decisions are a crucial part of storm chasing. Sometimes they are easy, sometimes they are tactical, and on rarer occasions safety is the risk that has to weighted up. Today's chase involved one such decision. I was at a closed iron cattle gate, it was hailing, with the odd golfball sized stone and lightning was frequent and close - do I get out of the car and open the iron gate, or do I simply turn around and backtrack 20 mins.

A trough system along the great divide was being fed by very moist NE winds. The NE wind would most likely rule out convection nearer the coast, and indeed low cloud sealed the coastal plains fate. A quick look at the latest satellite showed that the low cloud only penetrated a little way inland. I targeted the Marulan area as I knew that it should be sunshine, just west of the cloud.

A small but vigorous updraft west of the Hume Highway at Marulan	Rock Hard anvil overhead from the storm in previous picture.

I arrived at Marulan with a small but vigorous storm forming just west of the Hume Hwy. Although the base was small, it was concentrated, and there were signs that the storm even at this early stage was trying to organise its inflow. Unlike the other storms on the day this storm did not move SE. It slowly grew and propagated N/NE ( see radar loop below ). There was only one road option that offered a chance to keep track with the updraft, and it was not a great one, a small dirt road. As I had the 4WD today I gave it a shot. I had only moved about 5 kms west when hail began to fall. For the next 20 minutes whilst driving north along the dirt track I was stuck under the hail core, whilst just to the west glimpses of rain free base teased me.

It was then that I came to the locked gate. The decision was not hard, an iron gate connected to several kilometres of wire fence in a strong lightning storm, rain and hail. In reality I probably would have taken my chances with the lightning if it had been dry, but the guarantee of a bath and perhaps a painful hit by hail was what actually kept me safe in the car.

I backtracked the 20 mins breaking through the core and into clear, but of course on the wrong side of the storm. The structure of a crisp updraft back to my north was impressive. The local creeks were in flash flood.

An updraft on the SW flank of the storm ( the weaker flank )	Approaching the storm for the second time on the Hume Hwy

Unfortunately the backtrack also meant that I had to join the melee of cars on the Hume Hwy, the busiest interstate in Australia. As I once again approached the storm it was evident that many drivers had come to grief, at first an isolated car off the road in the bush, then a semi trailer jackknifed. Flash flooding had left sheets of water across the road, but many drivers still insisted on driving the full 110kph ( 70 Mph ) limit. Further north and into the core and I came across a section where 99% of the traffic had pulled over in an attempt to escape hail.

The storm now moved east of the highway and encountered the low cloud and coastal inversion, the storm fell apart rapidly.

Radar Images courtesy of Bureau Of Meteorology, Click to animate ( 350kb )

The area to watch is between Marulan and Bowral - note the movement compared with other storms.