Your most welcome Delly D,as this is exactly why I started this thread.

there was a tornado in Bowen in 1876 and a tornado in Mackay during the "small" cyclone that smashed up Bowen during the 1950s

Currently the Coral Sea has a couple of factors in place for a cyclone to form.

SST's are well above the tempratures required, shear is non existant and the upper winds have swung into favour, just need something to kick it off like a tropical depression and a bit of storm activity and who knows?

i totally agree that when TCs come ashore they should issue tornado watches it seems with many tcs when they cross they have embedded tornadoes in them

I've asked this question in the Cyclone Heidi thread, but it has gone unanswered.

Heidi was still a Cat 1 cyclone as she neared Wittenoom, some 210 km inland. Going by the radar it looks like at 12:50 WST she formed a new eye, which persisted and grew ever larger until it tore apart at 19:00 WST.

I thought the conditions that far inland over a desert would be all wrong for an eye to form? Or am I missing something?



See : 512km Radar Loop for Port Headland, 23:00 10/01/2012 to 13:00 12/01/2012 UTC

Hey Jax,

I have read and understood that cyclone form a true visible eye on sat images at Cat 3 level and above where it opens out and there is a cloud free region with in the centre of the system.

What that radar depicts I guess is still the rotating LLCC Low Level Circulation Centre which I gues on a radar looks to be an eye but its just a point of circulation. Also as the distance from the radar to the LLCC increases the radar may struggle to receive return signals due to heavier rain between the two as well as pure distance. This may have increased that appearance aswell. Pretty remarkable though that Heidi has stayed so intact for such a long distance inland. I think Yasi last year actually made it to Central Australia intact too. Amazing things hey.

Hi Jax I was in the middle of answering that question and lost power so Interwebs fell over.

OK The eye is still visible and in a Cat 1 that is a rarety but not unheard of. Cyclones can tarvel a great distance over land as a cyclone.

Have a look at http://www.bom.gov.au/cgi-bin/silo/cyclones.cgi hover your mouse over the blue track (Cyclone George) and you will see how far this one went before it faded into a depression (the X) There are a great many that have travelled at lot further distance than George did. Just cycle through teh trackmaps in the link above.

Hi all & thanks for starting this thread.
One thing I was confused about during Yasi (and at the time, a number of people on the forum noticed the same thing) was that at ground level in a number of places, there was no wind at all, but it was howling at roof level. This was particularly noticable in various parts of Cairns, going by the posts. The resulting lack of damage below roof level in various suburbs also seemed to confer with this observation. Could anyone give me an insight as to what was happening there?
The only reason I have been given so far was that the cyclone was moving very fast & creating its own 'updraft', therefore creating a type of vacuum at ground level. Thoughts anyone?

I could have a stab at it. Maybe it was due to a similiar concept to that of a hovercraft which is explained here.

"How does the air cushion beneath the hovercraft allow the vehicle to glide so freely? The key to the ease of movement is reducing friction. Vents of slowly moving, low-pressure air are ejected downwards against the surface close below it creating the air cushion. The trapped air cushion greatly reduces the friction of the vehicle, allowing it to glide freely upon the smooth surface below. "

Bit like Yasi with the winds flowing down off the surrounding hills forcing lower pressure into the coastal areas/valleys and enabling Yasi to slide over the top????

Out there concept but could be achievable on a big cyclonic scale.

Thanks for the replies Popeye and SBT. But I'm still a bit lost, please bear with me.

You've both mentioned Yasi, as well as your example with George SBT, both category fives when they crossed. Given Heidi was a category two, I'm guessing she's done well to travel so far intact. I'll check the link you provided SBT and see if I can find any others (cat 2s) that have done the same thing. From memory, have either of you seen a Cat 2 cyclone travel so far inland intact before?

Popeye, your explanation makes a lot of sense regarding the heavy rain making returns difficult the further it gets from the radar. But on thinking about it, I'm wondering why the radar would be able to read returns on the other side of that dead spot (or eye, or blank bit, or whatever) if the heavy rain on the radar side of that spot is the reason the spot is showing in the first place? Lol, hope that makes sense.

I've noticed these blank spots above the radar before, but not away from it like this one and its got me intrigued.

It isn't unusual for this eye to continue to be seen on radar for quite a long way inland as the tight circulation is maintained. As in this case it was a cat 2 when it crossed the coast and remained pretty well a tight system for some time, gradually losing shape and form until it died from a lack of 'fuel'.
Cat 1's rarely have a decent eye that you can see and you are right, the stronger teh system the longer it will have an eye that you can see clearly.


Winds:
Yasi etc can cause local ground effects similar to what you are talking about Popeye.
To eleborate. The topography (trees, hills, buildings etc) can have the effect of lifting the winds over structures and causing a lifting of the winds a couple of meters above ground level (Drag or friction). I must point out though that flat areas such as coastal plains with little vegetation means this has no effect on lifting the winds and they will be a simialr speed 10cm abover the ground as they will be at 10 metres until the hit an obstruction like a forrest or a ridge, moutain range etc.

In Townsville during Yasi you could hear the winds screaming overhead at much greater speeds that they where at ground level. I recorded 147kph winds (before nextdoors mahogany tree fixed ir for me) from my anonmeter which is 9 meters above ground level but at ground level the speed was down to under 80 kph due to the surrounding homes and trees.

But, more often than not with a Cat 1 even over the ocean the eye cannot be easily seen.

Thanks Popeye & SBT- that makes sense to me.

So SBT, are you saying that what is showing on the radar is actually an eye? If so, that's what's got me scratching my head. If you watch the loop I linked above, that eye seems to form on the radar several hours after crossing, not before, and then after several more hours gradually loses shape way out near Wittenoom. It's difficult to make out an actual eye on the radar prior to or during the crossing, but appears to open up beautifully later at about Yandeyarra

I haven't discounted Popeye's suggestion, but am still unsure as to why the radar wouldn't see the area in the centre of the system as it moves away, but would still see the far side of it.

Ha, so much for checking it out on the satellite images. Seems the satellite was having quite the dummy spit throughout almost the entire event.

http://realtime2.bsch.au.com/vis_sat2.ht...01201131233#nav