The Intersection

i-9336da3cf74156b226dd9f4b294c8d96-George Track BOM.gif

Earlier today, it looked like we were going to have a very intense cyclone off the northwestern coast of Australia. Now it looks worse: Cyclone George has turned south and is expected to strike the Pilbara region somewhere between Onslow and Port Hedland in the next 24 to 36 hours.

A lot now depends on how much George intensifies before landfall. The numbers in the image above, from the Bureau of Meteorology, are on the Australian scale. The current prediction is for a Category 2 storm on the Saffir-Simpson scale, but intensity prediction is tricky and not that reliable….

Comments

  1. #1 Blair Trewin
    March 8, 2007

    If an intense cyclone is going to hit anywhere this isn’t a bad place for it to hit – most of the population along this coast lives in relatively new towns built to service the mining industry (which only really got going in the 1960’s), and the building codes are strict enough that somewhere like Karratha should be able to come through a category 3-4 with mostly low-level damage. It’s certainly much less vulnerable than the Queensland coast (which is just as well because it gets hit much more often). Exmouth took a direct hit from a category 5 (Vance) in 1999 and sustained only moderate damage, with no significant injuries IIRC.

    The main impact is likely to be the cost of the shutdown of the offshore oil and gas platforms and the ports servicing the mines – which can easily run to $100 million or more per day. In very active seasons like 2005-06 this can make quite an impact on the profits of the companies concerned (even behemoths like BHP Billiton which make $10 billion-plus per year).

  2. #2 Blair Trewin
    March 8, 2007

    Made my last posting before I saw the developments of the last few hours – both the rapid intensification and the eastward shift of the track. Port Hedland has more older buildings than Karratha has, but has still been through something like this before (Joan, 1975). I don’t know enough about the local coastal topography to know how vulnerable it is to storm surge.

    An automatic weather station on Bedout Island was still reporting (with sustained winds of 195 km/h) as of 1000 UTC. If it keeps reporting (and especially if there’s 1- or 10-minute data logged on-station in addition to the hourly reports) this will be extremely valuable data – because there is no aircraft reconnaissance in the Australian region there are only a handful of cyclones with any data to allow ground-truthing of Dvorak number/wind/pressure relationships.

  3. #3 Chris Mooney
    March 8, 2007

    Folks,
    The rapid intensification Blair is talking about has the storm at a Saffir-Simpson Category 2 right now, and there’s some more intensification expected before it makes landfall:
    http://tsr.mssl.ucl.ac.uk/tracker/dynamic/200717S.html

    The Bureau of Meteorology sounds very concerned about significant storm surge:

    “Residents on the coast between Sandfire Roadhouse and Whim Creek including Port Hedland, are specifically warned of the potential of a VERY DANGEROUS STORM TIDE as the cyclone crosses the coast. On the current track Port Hedland is specifically under threat. Tides are likely to rise significantly above the normal high tide mark with very dangerous flooding and damaging waves.”

    http://www.bom.gov.au/products/IDW60281.shtml

  4. #4 Alex
    March 8, 2007

    Oh mate! that’s gonna hurt. I used to work in that neck of the woods – well, lack of woods. The topography down on the coast is dead flat, and the town is right round the harbour, although there’s a bit more height on the sea side.

    Looks like Marble Bar’s going to catch it further inland, too.

  5. #5 llewelly
    March 8, 2007

    George is making landfall. 1211 UTC 08/03/2007 TC technical summary from the Australian BOM has George with 10-minute maximum winds at 105 kts. The typical conversions from 10-minute max winds to the 1-minute max winds used for Saffir-Simpson categories are 1/0.9 and 1/0.88 . Either 115 kts, or 120 kts, after rounding to the nearest 5 kts . Category 4. (Based on observations from Bedout Island, they say, and in agreement with Dvorak rating of 6.0) JTWC has George at 110 kts, or cat 3 (Note – for Chris’s count of category 4-5 storms, this is a cat 3, as he’s used JTWC all along.)

  6. #6 Chris Mooney
    March 8, 2007

    Hi Llewelly,
    Well, last year it was debatable whether Larry was a Cat 3 or a Cat 4….I guess this year, we may have to say the same for George.

    Damn Australian storms.

  7. #7 Alex
    March 8, 2007

    The Port Hedland weather radar has been offline since, well, not long after landfall.

  8. #8 Blair Trewin
    March 8, 2007

    Bedout Island was only sending reports hourly, so the 105-knot sustained winds reported may well be lower than the highest they got in between observations. I’m hopeful that higher-resolution info is stored on station and can be downloaded after the event. From radar the eye went straight over the top of them.

  9. #9 Barry Cargill
    March 10, 2007

    There was very little structural damage to buildings in Port Hedland and South Hedland from my observations. Certainly light galvanised steel framed houses appeared to stand up well. Some older buildings with timber framed rafters (either termite ridden or not) and corrugated steel sheet roofing (in Port Hedland) however, succumbed.

    In South Hedland, a number of houses were damaged by fallen trees.

    Lesson to be learned – to withstand a cyclone – all structures – covered areas, fences need to be adequately designed and properly fastened in place.

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