Michael Thompson's Australian Storm Chase Diary
13th October 2002 - Non Severe storms, Southern Highlands, NSW
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You can run all the models and do the calculations but sometimes things don't go according to the script. Today was such a day. Lift Index was close to -6C, CAPE was going to be over 1000, perhaps higher. The models indicated good humidity, although I doubted the predicted surface winds could sustain the moisture levels. However the surface winds were expected to be light, so I held faith.
Early convection around midday held promise with a storm going briefly severe on the south coast. I was uncertain what direction to chase. I knew that the south coast storm was close to passing out to sea, but may back build as well. The other choice was to go up to the southern highlands where I was certain that storms would form. I choose the second option when a congestus tower formed into a weak anvil in just a few minutes in front of me.
The wind on the coast was a humid NE, passing up the escarpment and onto the southern highlands imagine my horror when I noticed that the wind was a 15 to 20 knot west. There are some simple basic rules you can apply to storm chasing SE Australia, one of them is you are unlikely to get a decent storm with a west wind if you east of the great divide. Despite what the models had indicated the surface winds were much stronger and low level moisture levels very much lower. The cumulus tried hard but had trouble forming into any organised storm structure. Isolated cells formed and went in minutes, just like popcorn.
I drove around the southern highlands for the next 4 hours looking form anything half decent. A line of weak storms came through from the west around 4pm. I was too far north the intercept the better storms and storms were moving from west to east in excess of 60 kph.
I headed back towards Bowral with the hope that something may break to Sydney's SW as it often does late in the day if there has been convection on the ranges nearby.
However close to sunset it was evident that the situation was stablising rapidly. I headed home instead.
On the way home I was treated to the sight of three large storms offshore, about 150 kms distant. One of these had a nice backshear. These storms told what may have happened in my chase area had the moisture levels been higher.