For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
Not sure if I can answer your questions.
Just an observation. Some of the areas listed as low risk of tropical cyclones in the south and south-west will still get a pounding from big winter storms, at times nearing the same wind-speeds as a Cat 1.
They didn’t believe in climate change when they drew the map?
An intermediate region would presumably expect to cop a cyclone more often than a normal region and less often than a cyclone region. So it seems adequate for now.
Bubblecar said:
An intermediate region would presumably expect to cop a cyclone more often than a normal region and less often than a cyclone region. So it seems adequate for now.
Yes. I’d say so but as deev’s pointed out, we’ll probably have to be ready to realign our thinking on it soonish.
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
I know, personally, the two people who designed these zones. Bill Melbourne and John Holmes.
They caused John, in particular, a lot of sleepless nights. They are designed using what is called the Gumbel Plot, https://en.wikipedia.org/wiki/Gumbel_distribution . What that means is that the probability distribution is not a “normal distribution” and is very far from a normal distribution at extreme values. This gives the wind velocity distribution an extra boost to account for uncertainties due to the limited length of time over which data is collected (often less than 100 years). And also contains a factor of safety to account for the fact that anemometers are not placed in the direct path of the cyclone.
To give you an example of the challenges faced by the pair, the wind speed results from Amberley air force base didn’t match up with other measured wind speeds. They found that the original instrument was designed to measure wind speed in knots and when the standard changed the air force just replaced the recording gauge with miles per hour without applying the necessary 15% speed correction.
As the amount of reliable data increases, our cetainty of the values will improve, and predicted exteme wind speeds must decrease. This factor of safety well and truly exceeeds any deterministic change due to climate change. Or to put it another way, the uncertainly due to climate change is already factored into the standard.
mollwollfumble said:
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
I know, personally, the two people who designed these zones. Bill Melbourne and John Holmes.
They caused John, in particular, a lot of sleepless nights. They are designed using what is called the Gumbel Plot, https://en.wikipedia.org/wiki/Gumbel_distribution . What that means is that the probability distribution is not a “normal distribution” and is very far from a normal distribution at extreme values. This gives the wind velocity distribution an extra boost to account for uncertainties due to the limited length of time over which data is collected (often less than 100 years). And also contains a factor of safety to account for the fact that anemometers are not placed in the direct path of the cyclone.
To give you an example of the challenges faced by the pair, the wind speed results from Amberley air force base didn’t match up with other measured wind speeds. They found that the original instrument was designed to measure wind speed in knots and when the standard changed the air force just replaced the recording gauge with miles per hour without applying the necessary 15% speed correction.
As the amount of reliable data increases, our cetainty of the values will improve, and predicted exteme wind speeds must decrease. This factor of safety well and truly exceeeds any deterministic change due to climate change. Or to put it another way, the uncertainly due to climate change is already factored into the standard.
> in the direct path of the cyclone.
Try that again. A correction to allow for the fact that anemometers are not often placed so that the strongest winds in the cyclone pass directly over the anemometer. And a correction to all for the fact that often anemometers are destroyed by cyclones because they’re not designed for wind speeds that strong.
So the three corrections together, those accounting for sampling errors due to the short length of data, the position of anemometer away from the strongest wind, and the destruction of anemometers by cyclonic winds, together apply a factor of safety to the standards that already covers climate change.
Consider for yourself. Suppose you want a 1% probability in 100 years. That’s a recurrence interval of 10,000 years. You only have 50 years of data to make that prediction from. That’s a representative problem that John Holmes and Bill Melbourne had to work with.
But not the only problem. John Holmes had to subtract off thunderstorm extreme winds to obtain cyclone extreme winds. It turns out that the two follow different Gumbel distributions. If you try to use the same Gumbel plot for both types of extreme winds together then the result can’t be fitted by a straight line on Gumbel plotting paper and the result would underestimate extreme cylonic winds. So the two sorts of extreme winds are separated out mathematically before plotting. Which they did, to more accurately predict cyclone extreme winds.
There is an extra factor of safety in the standard that I didn’t realise until long after I stopped corresponding with Bill and John. That’s the factor of safety associated with distance from the coast. Wind speeds drop off very rapidly inland with distance from the coast. To the extent that by landfall a lot of the wind speed has already been lost. So, for example, the cyclonic wind speeds measured at Magnetic Island are used for prediction of cyclonic wind speeds at Townsville. But being off the coast, cyclonic wind speeds at Magnetic Island are considerably larger than those on the coast, such as at Townsville. This provides an added (fourth) factor of safety.
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
The bulk of people will buy the cheapest house, and the cheapest house is the one made to just conform to the standards.
mollwollfumble said:
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
I know, personally, the two people who designed these zones. Bill Melbourne and John Holmes.
They caused John, in particular, a lot of sleepless nights. They are designed using what is called the Gumbel Plot, https://en.wikipedia.org/wiki/Gumbel_distribution . What that means is that the probability distribution is not a “normal distribution” and is very far from a normal distribution at extreme values. This gives the wind velocity distribution an extra boost to account for uncertainties due to the limited length of time over which data is collected (often less than 100 years). And also contains a factor of safety to account for the fact that anemometers are not placed in the direct path of the cyclone.
To give you an example of the challenges faced by the pair, the wind speed results from Amberley air force base didn’t match up with other measured wind speeds. They found that the original instrument was designed to measure wind speed in knots and when the standard changed the air force just replaced the recording gauge with miles per hour without applying the necessary 15% speed correction.
As the amount of reliable data increases, our cetainty of the values will improve, and predicted exteme wind speeds must decrease. This factor of safety well and truly exceeeds any deterministic change due to climate change. Or to put it another way, the uncertainly due to climate change is already factored into the standard.
Interesting, and thanks for the background, but:
“Or to put it another way, the uncertainly due to climate change is already factored into the standard.”
I very much doubt that is true, especially at the region boundaries.
The trouble with uncertainty is that it can go either way.
Dark Orange said:
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
The bulk of people will buy the cheapest house, and the cheapest house is the one made to just conform to the standards.
“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
Dark Orange said:
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
The bulk of people will buy the cheapest house, and the cheapest house is the one made to just conform to the standards.
This.
The Rev Dodgson said:
Dark Orange said:
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
The bulk of people will buy the cheapest house, and the cheapest house is the one made to just conform to the standards.
“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
I’d say you’d at least be thinking about it.
The Rev Dodgson said:
Dark Orange said:
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
The bulk of people will buy the cheapest house, and the cheapest house is the one made to just conform to the standards.
“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
If the event were significant enough, it would change the standards. And besides, that’s what insurance is for. And unless the insurance company gives me significanr discount on my premium, why should I spend the extra money on reducing their risk?
roughbarked said:
The Rev Dodgson said:
Dark Orange said:The bulk of people will buy the cheapest house, and the cheapest house is the one made to just conform to the standards.
“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
I’d say you’d at least be thinking about it.
The ways of standards committees are slow and steady, but they wouldn’t win many races.
The Rev Dodgson said:
roughbarked said:
The Rev Dodgson said:“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
I’d say you’d at least be thinking about it.
The ways of standards committees are slow and steady, but they wouldn’t win many races.
The Rev Dodgson said:
roughbarked said:
The Rev Dodgson said:“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
I’d say you’d at least be thinking about it.
The ways of standards committees are slow and steady, but they wouldn’t win many races.
slow and steady now.
Dark Orange said:
The Rev Dodgson said:
Dark Orange said:The bulk of people will buy the cheapest house, and the cheapest house is the one made to just conform to the standards.
“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
If the event were significant enough, it would change the standards. And besides, that’s what insurance is for. And unless the insurance company gives me significanr discount on my premium, why should I spend the extra money on reducing their risk?
One reason is that insurance only covers the direct monetary cost (and probably doesn’t even cover all of that).
There are many significant costs that are not covered.
“In theory” insurance companies should give you a significant discount if you can show your property is well above minimum standards, but I suspect it doesn’t work like that.
The Rev Dodgson said:
Dark Orange said:
The Rev Dodgson said:“It wouldn’t be right to change practice on the basis of a single event “
Sure it is. If that event significantly changes the best estimate of the “maximum considered event” (to use earthquake design terminology), why wouldn’t you change practice?
If the event were significant enough, it would change the standards. And besides, that’s what insurance is for. And unless the insurance company gives me significanr discount on my premium, why should I spend the extra money on reducing their risk?
One reason is that insurance only covers the direct monetary cost (and probably doesn’t even cover all of that).
There are many significant costs that are not covered.
“In theory” insurance companies should give you a significant discount if you can show your property is well above minimum standards, but I suspect it doesn’t work like that.
The Rev Dodgson said:
mollwollfumble said:
dv said:
For construction purposes, Zones C and D are the cyclonic wind zones. Kalbarri is shown as a red dot in Zone B (“intermediate”).
It wouldn’t be right to change practice on the basis of a single event but one does hope that these zones are designed with an eye to the future with regard to climate change.
I know, personally, the two people who designed these zones. Bill Melbourne and John Holmes.
They caused John, in particular, a lot of sleepless nights. They are designed using what is called the Gumbel Plot, https://en.wikipedia.org/wiki/Gumbel_distribution . What that means is that the probability distribution is not a “normal distribution” and is very far from a normal distribution at extreme values. This gives the wind velocity distribution an extra boost to account for uncertainties due to the limited length of time over which data is collected (often less than 100 years). And also contains a factor of safety to account for the fact that anemometers are not placed in the direct path of the cyclone.
To give you an example of the challenges faced by the pair, the wind speed results from Amberley air force base didn’t match up with other measured wind speeds. They found that the original instrument was designed to measure wind speed in knots and when the standard changed the air force just replaced the recording gauge with miles per hour without applying the necessary 15% speed correction.
As the amount of reliable data increases, our cetainty of the values will improve, and predicted exteme wind speeds must decrease. This factor of safety well and truly exceeeds any deterministic change due to climate change. Or to put it another way, the uncertainly due to climate change is already factored into the standard.
Interesting, and thanks for the background, but:
“Or to put it another way, the uncertainly due to climate change is already factored into the standard.”I very much doubt that is true, especially at the region boundaries.
The trouble with uncertainty is that it can go either way.
But factors of safety only go one way. All the uncertainty is included within those factors of safety.
As more data arrrives, so uncertainty decreases. As uncertainty decreases, factors of safety can be reduced.
If you saw just how much effort went into getting those zones quantified to cope with all possible sources of uncertainty, you’d laugh at climate change.
mollwollfumble said:
The Rev Dodgson said:
mollwollfumble said:I know, personally, the two people who designed these zones. Bill Melbourne and John Holmes.
They caused John, in particular, a lot of sleepless nights. They are designed using what is called the Gumbel Plot, https://en.wikipedia.org/wiki/Gumbel_distribution . What that means is that the probability distribution is not a “normal distribution” and is very far from a normal distribution at extreme values. This gives the wind velocity distribution an extra boost to account for uncertainties due to the limited length of time over which data is collected (often less than 100 years). And also contains a factor of safety to account for the fact that anemometers are not placed in the direct path of the cyclone.
To give you an example of the challenges faced by the pair, the wind speed results from Amberley air force base didn’t match up with other measured wind speeds. They found that the original instrument was designed to measure wind speed in knots and when the standard changed the air force just replaced the recording gauge with miles per hour without applying the necessary 15% speed correction.
As the amount of reliable data increases, our cetainty of the values will improve, and predicted exteme wind speeds must decrease. This factor of safety well and truly exceeeds any deterministic change due to climate change. Or to put it another way, the uncertainly due to climate change is already factored into the standard.
Interesting, and thanks for the background, but:
“Or to put it another way, the uncertainly due to climate change is already factored into the standard.”I very much doubt that is true, especially at the region boundaries.
The trouble with uncertainty is that it can go either way.
But factors of safety only go one way. All the uncertainty is included within those factors of safety.
As more data arrrives, so uncertainty decreases. As uncertainty decreases, factors of safety can be reduced.
If you saw just how much effort went into getting those zones quantified to cope with all possible sources of uncertainty, you’d laugh at climate change.
Two words. Risk Management.
mollwollfumble said:
The Rev Dodgson said:
mollwollfumble said:I know, personally, the two people who designed these zones. Bill Melbourne and John Holmes.
They caused John, in particular, a lot of sleepless nights. They are designed using what is called the Gumbel Plot, https://en.wikipedia.org/wiki/Gumbel_distribution . What that means is that the probability distribution is not a “normal distribution” and is very far from a normal distribution at extreme values. This gives the wind velocity distribution an extra boost to account for uncertainties due to the limited length of time over which data is collected (often less than 100 years). And also contains a factor of safety to account for the fact that anemometers are not placed in the direct path of the cyclone.
To give you an example of the challenges faced by the pair, the wind speed results from Amberley air force base didn’t match up with other measured wind speeds. They found that the original instrument was designed to measure wind speed in knots and when the standard changed the air force just replaced the recording gauge with miles per hour without applying the necessary 15% speed correction.
As the amount of reliable data increases, our cetainty of the values will improve, and predicted exteme wind speeds must decrease. This factor of safety well and truly exceeeds any deterministic change due to climate change. Or to put it another way, the uncertainly due to climate change is already factored into the standard.
Interesting, and thanks for the background, but:
“Or to put it another way, the uncertainly due to climate change is already factored into the standard.”I very much doubt that is true, especially at the region boundaries.
The trouble with uncertainty is that it can go either way.
But factors of safety only go one way. All the uncertainty is included within those factors of safety.
As more data arrrives, so uncertainty decreases. As uncertainty decreases, factors of safety can be reduced.
If you saw just how much effort went into getting those zones quantified to cope with all possible sources of uncertainty, you’d laugh at climate change.
That’s just wrong, and amount of effort has nothing to do with it.
For instance, after the Christchurch earthquakes the design earthquake for that region increased substantially.
The Rev Dodgson said:
mollwollfumble said:
The Rev Dodgson said:Interesting, and thanks for the background, but:
“Or to put it another way, the uncertainly due to climate change is already factored into the standard.”I very much doubt that is true, especially at the region boundaries.
The trouble with uncertainty is that it can go either way.
But factors of safety only go one way. All the uncertainty is included within those factors of safety.
As more data arrrives, so uncertainty decreases. As uncertainty decreases, factors of safety can be reduced.
If you saw just how much effort went into getting those zones quantified to cope with all possible sources of uncertainty, you’d laugh at climate change.
That’s just wrong, and amount of effort has nothing to do with it.
For instance, after the Christchurch earthquakes the design earthquake for that region increased substantially.
roughbarked said:
The Rev Dodgson said:
mollwollfumble said:But factors of safety only go one way. All the uncertainty is included within those factors of safety.
As more data arrrives, so uncertainty decreases. As uncertainty decreases, factors of safety can be reduced.
If you saw just how much effort went into getting those zones quantified to cope with all possible sources of uncertainty, you’d laugh at climate change.
That’s just wrong, and amount of effort has nothing to do with it.
For instance, after the Christchurch earthquakes the design earthquake for that region increased substantially.
It would seem smarter to just shift Christchurch.
Where to?
Its still in one of the lowest risk areas of NZ.
The Rev Dodgson said:
roughbarked said:
The Rev Dodgson said:That’s just wrong, and amount of effort has nothing to do with it.
For instance, after the Christchurch earthquakes the design earthquake for that region increased substantially.
It would seem smarter to just shift Christchurch.
Where to?
Its still in one of the lowest risk areas of NZ.
Well there is that.
Bubblecar said:
An intermediate region would presumably expect to cop a cyclone more often than a normal region and less often than a cyclone region. So it seems adequate for now.
It’s actually defined by maximum expected wind speed, not frequency of cyclones. It’s a bit complicated because you have to allow for terain and topography…
But a coastal area in zone B will mostly be built for N2: “serviceability “ to 26 m/s and “ultimate” to 40 m/s. Those = 93km/h and 144km/h. .
dv said:
Bubblecar said:
An intermediate region would presumably expect to cop a cyclone more often than a normal region and less often than a cyclone region. So it seems adequate for now.
It’s actually defined by maximum expected wind speed, not frequency of cyclones. It’s a bit complicated because you have to allow for terain and topography…
But a coastal area in zone B will mostly be built for N2: “serviceability “ to 26 m/s and “ultimate” to 40 m/s. Those = 93km/h and 144km/h. .
Ah.
Bubblecar said:
dv said:
Bubblecar said:
An intermediate region would presumably expect to cop a cyclone more often than a normal region and less often than a cyclone region. So it seems adequate for now.
It’s actually defined by maximum expected wind speed, not frequency of cyclones. It’s a bit complicated because you have to allow for terain and topography…
But a coastal area in zone B will mostly be built for N2: “serviceability “ to 26 m/s and “ultimate” to 40 m/s. Those = 93km/h and 144km/h. .
Ah.
First Binge hit on AS 4055:
https://staconsulting.com.au/wind-classification-housing-4055-vs-1170-2/#:~:text=AS%204055-2012%20Wind%20loading%20for%20housing%20This%20is,classification%20for%20one%20or%20two%20storey%20housing%20only.
which looks like it is quite relevant to the current discussion.
Just to broaden the discussion, when the poles switch cyclones will spin the other way.
Peak Warming Man said:
Just to broaden the discussion, when the poles switch cyclones will spin the other way.
Yes.
