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Severe tropical storms are known in different geographic areas as
cyclones (South Pacific), typhoons (Asia) and hurricanes (Caribbean),
just different names for the same circular low-pressure systems that
are born in warm tropical waters and, while rotating with great
destructive force, move across sea or land slowly and unpredictably.
As they cross land they tend to lose strength, although it is not
unknown for them to veer back out to sea and regain ferocity.

They are a feature of life in our tropical north, just as they are in
other tropical areas. These days, the building code for constructions
up there is supposed to ensure "cyclone-proof" buildings - as if there
was such a thing. After every good storm there are examples of these
rigidly reinforced buildings that have been destroyed, sometimes next
door to somewhat more pliable old timber framed, corrugated
sheet-metal clad shacks many decades old, that have seen more than
their fair share of storms come and go. But I digress.

While the effects of  a good 'southerly buster' can be similar to
those of a severe tropical storm, they are quite different weather
systems. Sydney, at about 34 degrees south, is well beyond the
tropical region. Southerlies are born out of depressions down in the
Southern Ocean and make their way up the east coast of Australia as a
cold front. They often create a dramatic change in the weather. They
can be seen arriving as a boiling line of dark cloud approaching from
the south, and in summer the temperature can drop from about 40
degrees Celsius (> 100d F) to less than 20 degrees (< 68d F) in a few
minutes, as howling wind and strong driving, almost horizontal rain
arrive. They can be quite brief - all over in a few minutes - or last
for days. In summer they can create a welcome diversion on hot and
sultry days; people talk about them 'clearing the air'.

The weather bureau - as reported by some media, such as radio stations
- tracks their progress and can predict their arrival at a given point
with some accuracy.

They tend to be a regular feature of the annual Sydney to Hobart ocean
yacht race. The typical summer fine weather wind is a north easterly
that grows in strength during the day, and throughout the afternoon
can blow consistently at 20-30 knots. Before these winds the yachts
fly to the south under spinnakers at a great rate of knots. But if a
southerly comes up the coast mayhem results - sails are shredded,
masts are broken and occasionally crew are lost overboard. It happens
on a regular basis. The arrival of a southerly also tends to dash any
hopes of making a record run to Hobart, as it can be very difficult to
make any progress to the south while the wind blows hard from there.

Navigation during yacht races these days is not so much about knowing
the location of the vessel, as that is a given (all that individual
boats, or anyone else for that matter, have to do is go to the
official race website where the position of each of the yachts is
updated constantly and displayed in real time). No, the real task of
the navigator is to know where the boat SHOULD be, in order to
minimise the effects of unfavourable weather systems, as one example,
or maximise the effects of the favourable current, for another.

I've always thought of southerlies as being part of summer weather,
although the recent severe storms from the south (another is expected
in the next few hours) have happened in winter, which is normally a
fairly dry period here. Strong dry winter winds normally come from the
west, the 'winter westerlies'. We think of these as being safe winds
that are easy to sail to, as the boat is often on some sort of beam
reach sailing up or down the coast, while the wind does its best to
push the boat away from the coast. The sailor feels encouraged to hug
the shore, which makes for a more interesting passage, although it
does tend to be a cold run.

Although the effects of the recent storm that pushed the Pasha Bulker
onto the coast were fairly devastating, widespread rain has been
falling in parts of Australia that have been in drought for years, so
not entirely unappreciated.

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