A live geography lesson

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V Williamson
Part of the furniture
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Joined: February 6th, 2008, 9:16 am

A live geography lesson

Unread post by V Williamson » June 6th, 2016, 9:09 am

I suppose most forumites will be acquainted with the east coast low that created heavy rainfall and strong winds from Queensland and through the NSW coast, and as I write, I understand has moved towards Victoria and Tasmania over the weekend just passed. By the way, all credit to those in the emergency services out in those conditions!

Years ago, I remember reading about low pressure systems which rotate clockwise in the Southern hemisphere. If I recall correctly, an English weather book described how a fishing boat might encounter strong winds from one direction as a low approached, then calmness as the low passed directly over followed by further strong winds coming from the opposite direction.

I have further read how such a phenomenon occurred during Darwin's Cyclone Tracy in 1974. I believe that when the low in Tracy passed over, it was calm and even stars could be seen in the sky.

So yesterday, amongst the heavy weather, and being on the NSW coast south of Sydney, it was interesting to note the winds were for most of the day coming from the North East or East as the low pressure cell was above us in latitude. My wife and I ventured out to the local beach less than 1km away about 9:00pm, a little after the highest tide of the year (which would have even been higher given the low barometric pressure) and the rain had stopped and it was calm. We were even able to get out of the car to briefly walk around with our torches for a better look. This must have corresponded with the low pressure cell being over us.

Back home, the wind began to rise and the rain come down again, and in textbook manner, the wind was from the west, corresponding to the cell having moved south of us. Yep, a live geography lesson I had not experienced before!

Shann Low
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Joined: April 2nd, 2014, 3:14 am

Re: A live geography lesson

Unread post by Shann Low » June 6th, 2016, 3:42 pm

When you do your ships masters quals there's a section specifically on tropical revolving storms (Cyclones) which goes exactly into all of that. If you can't outrun a cyclone at sea (and a lot of trawlers designed to pull nets slowly cannot) then you have to know what quadrant to aim your vessel for to get the best possible chance of surviving it as it passes.

nilla60
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Joined: May 13th, 2007, 12:09 am

Re: A live geography lesson

Unread post by nilla60 » June 6th, 2016, 8:42 pm

The satellite image yesterday was pretty gnarly, there was a full on eye developing, so I'm not surprised. Literally the eye of the storm.

I love this web site, it uses the Mean Sea Level Pressure chart to animate the resulting winds.

https://earth.nullschool.net/#current/w ... -24.53,754

Shann Low
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Posts: 765
Joined: April 2nd, 2014, 3:14 am

Re: A live geography lesson

Unread post by Shann Low » June 7th, 2016, 1:56 am

Bookmarked that one Nilla - that's awesome. :thumb:

Cheers for that!

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