Topic: Southerly Change Roll Cloud

[Michael Bath]

Looking through the VIS images from yesterday (3rd Oct) and came across a nice example of a roll cloud that has formed as a result of a southerly change moving up the NSW coast.

Click image for 250 metre resolution MODIS image.




An example of a roll cloud in Sydney:



more here

Michael

[Michael Bath]

Here is another example - off the Northern NSW coast 16th Sep 2008. All the VIS images so far today have shown a similar cloud pattern to this one

[Mike]

Huge distance it covers also, MB.  Would have looked spectacular.  Are there any other photos that you or anyone else managed to get.  I enjoy seeing these cloud formations as they hang off in mid air it seems, so the more pics the better.

Do you know when this roll cloud started to form - over the ocean or at first over land?

[Michael Bath]

Infrared satpics suggest the roll cloud may have formed near Sydney about 11pm last night - so quite an impressive example. They really only show up properly on the VIS images so hard to say for sure whether it was present during the night.

There are no photos of today's roll cloud from ground level as it would be near impossible with a nasty dust haze over the area.

[Mike]

Thanks.  The sat image is quite impressive and what a subject to photograph!  To ask a question...was this associated with an storm activity or just a temperature phenomena for convective purposes?

[Richary]

Years ago at Gosford photoed something similar moving up from the south. The front of the cloud was visibly rolling down to underneath where it was mammatus, then as the cloud went over you could see the cloud rolling back upwards. Probably 2-3km wide as it went over.

Didn't have video facilities at the time, and I have since lost all the 35mm photos I used to own due to a bad experience with a past girlfriend in Adelaide, I did take some shots of it so that is a shame.

[Michael Bath]

The roll cloud develops along the area of low level convergence. In the case yesterday we had N-NE winds and then southerly winds behind the change. In many cases yes - you get lots of thunderstorms - but in this case the air was very dry and capped too - so all you get is the roll cloud. There was also cirrostratus present as you can see in the satpic.

MB

[James]

Jimmy may remember this day - 31 October 1999. We watched a southerly change move up the coast over Sydney with something that looked very much like a roll cloud on the leading edge of the front. I haven't seen anything like it since. I imagine they must look spectacular out to sea when covering the entire horizon.