Author Topic: Observations of a Strong Southerly Buster at Braidwood 23/12/2006  (Read 4177 times)

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Offline Harley Pearman

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Hello all.

During my recent visit to Braidwood / Batemans Bay 23/12/2006 I was able to observe for the first time some dynamics of a strong southerly buster moving north along the south coast.

This weather event being a Southerly Buster is worth noting because they are capable of generating strong and very sudden wind changes at the boundary.

I left Goulburn at approximately 11 am under a partly cloudy sky and travelled south along the Taralga Road towards Braidwood. Conditions were fair but cloudy and relatively warm with reasonable NW winds blowing.

As I approached Braidwood from the NW I noted a significant southerly buster moving north along the NSW South Coast so I decided to approach it from the north west. Given the altitude of that region (Braidwood) at between 600 to 800 metres above sea level, I could in places look down onto the leading boundary of the southerly buster as it moved north along the coast.

The boundary of this change was marked by a thick deck of low stratus clouds and I could look down on that too in places.

This is something that I have never seen before. Effectively given my altitude, I was looking down from above on a cold front that was moving north.

At Braidwood and nearby areas, I noted that the southerly buster moved freely north along the coast because there are / were no obstacles to block it however, it had difficulty rising up over the coastal mountains.

The southerly buster often trails a thick layer of low stratus clouds and occasional drizzle can fall from this cloud deck. However in this instance, I observed some very unique features being:-

a) - A weak thunderstorm cell moving from west to east collapsed rapidly or weakened into a large rain cell as soon as it crossed the boundary and land affected by the southerly buster.

b) - Some larger cumulus clouds built up around Braidwood but as they neared the edge of the cool change (The southerly buster) lying just to the east of town they dropped rain showers on the escarpment of the coastal mountains and some became quite heavy. No lightning was observed. These showers weakened as they travelled further east out to sea.

Hence the southerly buster was affecting the way clouds were developing and the rainfall.

Eventually the southerly buster was able to climb over the coastal ranges and slowly tracked inland but the stratus clouds became broken and a significant amount of turbulence was observed in the clouds and sky surrounding Braidwood and areas further north and south inland from the escarpment.

The low stratus clouds being approximately 100 to 200 metres above me were rising into cumulus clouds with part of the cloud towers moving west and part moving east.

I also noted that the southerly buster never penetrates much beyond the coastal mountains and I saw that occur at Braidwood.

I am aware of some recent research on the southerly buster done at Batemans Bay and they can be quite violent on the south coast. For the first time, I observed this violence (Mainly the sudden wind changes and how topography affects their movement).

I eventually had to descend through the southerly buster on Clyde Mountain descending into Batemans Bay and it was an experience especially with the heavy rain showers that were occurring.

Amazingly once I drove below the cloud layer, the winds were calmer with lighter rain / drizzle as I neared Batemens Bay.

Harley Pearman