it's surprising how the wind appears to be swinging back and forth from relatively calm to blowing dogs off chains

@ haircut, yeah looking around at the different observation points the winds all over the place. i guess the squall lines are so big it's a lottery at this stage.

hey cheers for the links!

@ eddy, no worries... as much as it's a bad omen for the crew up north, as windworshippers it's hard not to watch.


latest bom has yasi hitting innisfail. south johnstone obs are worth keeping an eye on. www.bom.gov.au/products/IDQ60801/IDQ60801.95292.shtml

Select to expand quote

sausage said...

Gestalt said...

^ not sure i follow ken,

isn't the windiest spot the eye wall....

Spot on Gestalt. Cloud cover shown on radar has no correlation to wind speed. Out of interest I read today that Yasi has an eye width of 30km which is massive compared to other (but just as powerful) systems.

I've experienced few close calls and near misses growing up in CQ, but if you are lucky enough to have the eye pass directly over they say it is the most surreal experience. One minute it is dark as night and screaming from the south at 100knots, then goes deadly still with bright sunlight beaming down through the clear sky above the eye, then it starts to blow but this time from the north. So everything that blew off or past you comes back again in the opposite direction to do even greater damage. Travelling at 30km and hour with an eye width of 30 km, someone will have an hour of calm inbetween the most terrifying 4 to 6 hours of their life.

you're on the money sausage. apparently eye is 38km

thanks for the links guys,
stay safe people. all the best.

latest update. yasi has intensified further with max wind gusts near the core measured at 135kn.

storm surges around cardwell of +7m above high tide mark.

latest bligh update. i'm starting to feel sorry for anna, she's been having to dish out a lot of bad news.

check out her comments on the power grid in the video.

Yes, she has not had many nights at home doing her own thing this year.
Reading between the lines, even though many of the trunk towers may be 100-150km inland, as the line approaches Cairns, it must get much closer to the coast.
There is certainly a major tower line passing directly through Atherton, cos i was quartered in Tower Avenue, in Tower Apartments, and it ran right up the street.
I think that it is a failure of centralisation that produces these risks.
Areas that should be self-sufficient in essential services have become vunerable because of the centralisation mania.

Select to expand quote

Gestalt said...

KenHo said...

Yeah, but Cairns will be all built to W54 or thereabout.
At Bundaberg we had to build to W52, which is 52m/sec wind speed. I think Bris is more like W28, though Gestalt or the other construction guys here will know for sure. The engineering involved in W52 is substantial so the homes will not go down like they did in Darwin.
The bigger issue here will be the storm surge, more so than the wind.
Inland towns like Atherton etc won't be built to the same cyclone rating though, and there are a lot of older homes there too.

JoLee said...

I'm so worried and praying for all my rellies in home town Cairns . Double the size of cyclone Tracy and she flattened Darwin.

it all varies depending on topography, sheltering, building height etc.

brisbane is generally w28-w41 non cyclonic in the old measure. that is now N1-N2-N3 and up on ranges would be around N4 or C1
bundaberg and north is where the cyclonic categories start. so they are C1-C2-C3 etc.

there are buildings in cairns that are only C1, but i've also done building in rocky that needed c3, basically anything close to the coast or higher up a range or in a very open area will see a higher rating. pressure also plays a part not just wind speeds.

basically C1, C2 C3 and C4 classifications are 50, 61, 74 and 86 m/s respectively

cyclone ratings are
cat 5 is >280km/hr or >78m/s
cat 4 is 225-280km/hr or 63-78m/s

or there abouts.

Hey Gestalt, you sound like you are in the building/design game and you mentioned pressure in the above quote, maybe you might know about roofs lifting off.
Spoke to my bro in tsv this afternoon and he said he has just finished boarding up hiis windows with ply. I asked him why, he said to stop stuff comming through his windows. I mentioned to him that when we were kids/teenagers growing up in NQ, the parents and every one else taped windows to prevent the glass shattering, but we didn't board up. The theory of the time was to open windows on the leeward side of the house to equalise the pressure inside and outside to prevent the roof from lifting off due to higher pressure inside the house, when the wind came back the other way, close then open on the new leeward side.
there were a lot of people boarding up on tv reports.
is the pressure thing an old wives tale or does it hold water.

also there is probably a lot of older houses in the north that predate cyclone tracey and althia that wouldn't have been built to any cyclone standards, maybe a few steel rods put in at the builders whim.

Select to expand quote

Gestalt said...

latest bligh update. i'm starting to feel sorry for anna, she's been having to dish out a lot of bad news.

check out her comments on the power grid in the video.

...Its 100 knots in Queensland, take that West Aussies!!

hi mate, i'm very reluctant to give advice on these things. so i'd say do more research additional to what i say here. also, i'm not and engineer, i'm a building designer. these days we don't design tie down/bracing/ wind ratings ourselves we pay qualified engineers to do it. but in the old days we did it ourselves so i've got some background.

cyclones... my familly comes froms central qld originally so i've been drilled from a young age in what to do in cyclones, been through a couple also. the advice among all of the typical stuff was to open windows on the leeward side to release pressure.

i don't believe though that modern thinking agrees with this. from what i understand it is best to keep everything shut and sealed. boarding up windows prevents them from being broken by flying debree which in turn prevents wind getting in.

you are most likely to loose your roof when the wind gets in as it pushes upwards on the ceiling in an effort to escape and increases or adds to the uplift forces being created from wind flowing over the roof. on a side note a flatter roof has less uplift.

so the worst case scenario in a cyclone is the wind getting into your house and lifting the roof, windows and especially garage doors are the weak spots. opening a window on the leeward side can provide an opening for the wind to enter as the wind is swirling around. a cyclone is a series of thunderstorms revolving around an eye so the wind can change direction rapidly. so in short keep it sealed.

regards the wind ratings. there is also wind pressure taken into acount, especially on windows as the need to stay sealed even under movement so there is usually a water penetration pressure specified as well as a limit state pressure.

i think one of the rules of thumbs with existing buildings is that they are existing so they've made it through cyclones before. not to say they will survive into the future though. what used to be practice with qld'ers in the older days was to pour concrete slabs bside the house and then run steel cables up over the roof from one side to the other during cyclones. this is what my great grandfather/grandfather did in rocky/north qld.

when you work out wind clasifications on building, which i don't do anymore as engineers are better qualified, you take into account all of the items mentioned in my post above. that is what dictates it's requirements and that can change dramatically from one location to another within the same town.

thanks Gesty, he said he didn,t understand why , but the norm is to board up these days, he's lived up there 10 years more than i have.
Just after i posted the last one , an engineer came on tv and explained things which included boarding up and keeping things closed, all foreign language to me didn't understand much of what he said, so I'll have to tell him sorry when i speak to him again and not to listen to his older brother, which he has never done anyway

on a lighter note he has just put up a house sized shed at toomulla bch just north of tsv, and hasn't had the final ispections yet so says he couldn't get insurance, his mrs is joking saying that its cyclone rated so they should get a newby under warranty if it is flattened i don't like their chances.

so i did some figures.

low islands registered 92km/hr - 50 knots (cat1)
cairns registered 85km/hr - 45knots (lower than cat 1)
townsville registered 120km/hr - 65 knots (high cat1 border cat2) with a big gust at cat2
lucinda registered 185km/hr - 100 knots - (cat 3)

there is no data for tully area so can't work it out. my guess is high cat4 at crossing