Michael Thompson's Australian
Storm Chase Diary
13th
October 2002 - Non Severe storms, Southern Highlands, NSW
Click
to enlarge any photo into separate window
|
|
Early
storms held promise.
|
With
this scene I thought that the legendary chaser Jimmy Deguara must
be close by.
|
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.
|