Storm Australian Severe Weather Forum
Severe Weather Discussion => General Weather - all topics not current severe weather. => Topic started by: Jimmy Deguara on 25 September 2007, 03:16:57 PM
-
Hi,
Whilst perusing the internet in search of particular facts about tornadoes, I came across these resources which is quite interesting given it is wikipedia. Including is a table of tornado information and links:
http://en.wikipedia.org/wiki/List_of_Southern_Hemisphere_tornadoes_and_tornado_outbreaks
http://en.wikipedia.org/wiki/Bulahdelah_tornado
There are of course links to other segments from the original link above.
Regards,
Jimmy Deguara
-
I came across this as well the other day when looking up the dates for a couple of the other major events.
There was no info that I could find about the time the Bulahdelah tornado occurred. After plotting charts from the GFS archives it appears to have occurred between 00z and 06z. Pretty impressive getting such cold upper air at the beginning of January.
There are no satpics or soundings available (online) this far back in time for Australia.
01/01/1970 00z
Instability: Lifted Index (http://australiasevereweather.com/storm_news/1970/maps/1970010100li.png)
Relative Humidity: 0300 (http://australiasevereweather.com/storm_news/1970/maps/1970010100rh0300.png) / 0500 (http://australiasevereweather.com/storm_news/1970/maps/1970010100rh0500.png) / 0600 (http://australiasevereweather.com/storm_news/1970/maps/1970010100rh0600.png) / 0700 (http://australiasevereweather.com/storm_news/1970/maps/1970010100rh0700.png) / 0850 (http://australiasevereweather.com/storm_news/1970/maps/1970010100rh0850.png) / 1000 (http://australiasevereweather.com/storm_news/1970/maps/1970010100rh1000.png)
Temperature: 0300 (http://australiasevereweather.com/storm_news/1970/maps/1970010100temp0300.png) / 0500 (http://australiasevereweather.com/storm_news/1970/maps/1970010100temp0500.png) / 0700 (http://australiasevereweather.com/storm_news/1970/maps/1970010100temp0700.png) / 0850 (http://australiasevereweather.com/storm_news/1970/maps/1970010100temp0850.png) / 1000 (http://australiasevereweather.com/storm_news/1970/maps/1970010100temp1000.png)
Winds (knots): 0300 (http://australiasevereweather.com/storm_news/1970/maps/1970010100wind0300.png) / 0500 (http://australiasevereweather.com/storm_news/1970/maps/1970010100wind0500.png) / 0600 (http://australiasevereweather.com/storm_news/1970/maps/1970010100wind0600.png) / 0700 (http://australiasevereweather.com/storm_news/1970/maps/1970010100wind0700.png) / 0850 (http://australiasevereweather.com/storm_news/1970/maps/1970010100wind0850.png) / 0925 (http://australiasevereweather.com/storm_news/1970/maps/1970010100wind0925.png) / 1000 (http://australiasevereweather.com/storm_news/1970/maps/1970010100wind1000.png)
01/01/1970 06z
Instability: Lifted Index (http://australiasevereweather.com/storm_news/1970/maps/1970010106li.png)
Relative Humidity: 0300 (http://australiasevereweather.com/storm_news/1970/maps/1970010106rh0300.png) / 0500 (http://australiasevereweather.com/storm_news/1970/maps/1970010106rh0500.png) / 0600 (http://australiasevereweather.com/storm_news/1970/maps/1970010106rh0600.png) / 0700 (http://australiasevereweather.com/storm_news/1970/maps/1970010106rh0700.png) / 0850 (http://australiasevereweather.com/storm_news/1970/maps/1970010106rh0850.png) / 1000 (http://australiasevereweather.com/storm_news/1970/maps/1970010106rh1000.png)
Temperature: 0300 (http://australiasevereweather.com/storm_news/1970/maps/1970010106temp0300.png) / 0500 (http://australiasevereweather.com/storm_news/1970/maps/1970010106temp0500.png) / 0700 (http://australiasevereweather.com/storm_news/1970/maps/1970010106temp0700.png) / 0850 (http://australiasevereweather.com/storm_news/1970/maps/1970010106temp0850.png) / 1000 (http://australiasevereweather.com/storm_news/1970/maps/1970010106temp1000.png)
Winds (knots): 0300 (http://australiasevereweather.com/storm_news/1970/maps/1970010106wind0300.png) / 0500 (http://australiasevereweather.com/storm_news/1970/maps/1970010106wind0500.png) / 0600 (http://australiasevereweather.com/storm_news/1970/maps/1970010106wind0600.png) / 0700 (http://australiasevereweather.com/storm_news/1970/maps/1970010106wind0700.png) / 0850 (http://australiasevereweather.com/storm_news/1970/maps/1970010106wind0850.png) / 0925 (http://australiasevereweather.com/storm_news/1970/maps/1970010106wind0925.png) / 1000 (http://australiasevereweather.com/storm_news/1970/maps/1970010106wind1000.png)
-
Michael,
What I find interesting about the year 1970 was that it was from what I recall statistically a cold winter - Richmond for instance acheieved its coldest morning on record of -8.3C. I assume that particularly cold air was advected north and perhaps made such a cut off low with such extreme temperatures possible that year.
That was one hell of a system!
Regards,
Jimmy Deguara
-
Wow, that is a nice set-up alright! Thanks for digging out those links above MB.
A couple of things caught my eye looking over those charts above. I would have thought the RH for 1000 and 850 would have been a little higher than around 50%. Is there any record of the LCL for that day? Probably not but thought I'd ask. Second thing is watching the surface low really develop between 00z and 06z. Quite awesome to see it take shape with increasing wind speeds around it as the upper cold pool approaches.
-
Hi James,
I have seen the actual report of this event and let me tell you the analysis was reasonably complex with a surface trough along the eastern part of the ranges. Supercells exploded along the line with cricket balls sized hail amongst a few of the storms. This storm for some reason developed very low bases and thence the giant tornado that followed!
Regards,
Jimmy Deguara
-
Hey guys,
Just stumbled across this post as well. AWESOME stuff. I've also read the official report and I believe there was a "double dry-line" set up in place which is not uncommon in situations such as this (in Australia). I know of at least 2 other instances of such events (with Sept 29, 1996 being one of them). Basically a trough (quasi-dryline) sets up to the east of the main trough...without thinking about it in any detail, i'm not sure what mechanism allows this to occur. DP's on this day to the east of the quasi-dryline were in excess of 20C (I think I recall even as high as 22C), whereas to the west of the quasi-dryline the DP's were in the mid-teens (say 16C). Then the main dryline further W sees the DP's drop to the low single figures W of this feature. Also, the surface winds on the eastern side of the quasi-dryline are generally north to north easterly (maybe even easterly depending on the position of the surface low), whereas west of the quasi-dryline, the surface winds are more north westerly with westerly or even south westerly winds following the main dryline. As you can see, this creates conditions which highly favourable for severe convection east of the quasi-dryline with greater turning in the lower levels and also much higher DP's allowing for greater instability.
Storms can and often will develop on the main dryline as well but these are less likely to be supercellular/tornadic given the more linear shear, however, they can still pack quite a punch as the upper levels are usually more unstable further back to the west nearer to the upper level low/cold pool and the shear is still quite strong.
And just to make things interesting, in this case where there is such a strong upper level low/cold pool, you may even get storms "in" the cold pool as well given that surface temperatures would be quite tasty in January and there may be enough residual moisture left over from storms to kick off more.
All bets are off when we get another set up like this. BRING IT ON!
Macca
-
Wow, that is a nice set-up alright! Thanks for digging out those links above MB.
A couple of things caught my eye looking over those charts above. I would have thought the RH for 1000 and 850 would have been a little higher than around 50%. Is there any record of the LCL for that day? Probably not but thought I'd ask. Second thing is watching the surface low really develop between 00z and 06z. Quite awesome to see it take shape with increasing wind speeds around it as the upper cold pool approaches.
I just noticed this discussion and in particular James's post. I have reactivated the part of my website (www.wthrman.com) in which people are able to plot historical severe weather parameters back to January 1948. I had withdrawn it a couple of years or more ago, basically due to what I assumed was a lack of interest.
The plots are taken from the NOAA site but on my site you only have to click a few buttons to get dates etc instead of typing it all in on the NOAA version..unless of course you like all that sort of stuff!
Unfortunately there are no archived CAPE data that I am aware of, however you can plot lifted index, surface maps and thickness, and a whole range of wind and moisture profiles at different heights. You can refine it to a single state, and also see plots for other parts of the world including the USA.
The site also has soundings from 1973, too late for this event of course but that may be useful for other events.
I have just tested it quickly for 1/1/1970 and it works. Click on the Severe Weather plotting option on the main page.
I hope it's helpful.
Cheers...Keith
-
Hi everyone,
I wanted to revive this thread to ask some questions that have bugged me about this event. It's hard to get much information on the net about this tornado and I am curious to know why an official fujita scale rating was never released publicly. Also to those who have seen the official review was there any photos of the tornado? what about the damage? Aerial photos of the path? I know it was 1970 and in Australia but it seems crazy to have a rare event like this with such little ionformation. This is literally the most information I can find.
"The Bulahdelah Tornado was an intense tornado which occurred near the town of Bulahdelah (100 kilometres (62.1 mi) north-northeast of Newcastle), New South Wales on 1 January 1970, and is thought to be the most destructive tornado ever documented in Australia.[1] It is thought to be least F4 or F5 on the Fujita scale however no official rating has been made public.[2][3]
The tornado left a damage path 22 kilometres (14 mi) long and 1–1.6 km (0.6–1 mi) wide through the Bulahdelah State Forest.[1] According to reports, it threw a two ton tractor 100 m (328 ft) through the air, depositing it upside down. It is estimated that the tornado destroyed over one million trees.[1] The weather system that produced the tornado was a classic set-up for violent tornadoes, something somewhat rarely seen outside of the United States, Canada, Bangladesh, and adjacent areas of India". - wikipedia.org
How acurate do you beleive this information to be?
The synoptic charts posted above are impressive to say the least. How often would a setup like this or similar occur in Australia?
-
Enak,
You are lucky the Bureau even has it on the database :)
Seriously, there was a report on the tornado from the Bureau but until the 1990's. Neverthless, the Bureau has not really rated tornadoes until the 1989 Elsmore, NSW tornado to my knowledge. Was the Brisbane tornado rated? Unless someone has seen the damage and done an appropriate survey, can you really rate a tornado?
Regards,
Jimmy Deguara
-
Enak,
I have wondered the exact same thing. Google searches send you straight to the wiki article or australian weather forums! Hardly the most reliable information out there (though still great for info). No hits in google scholar or web of science so it doesn't appear that any papers have been published regarding this event. Looking at the analysis charts posted I have little doubt that this day was a significant weather event for parts of eastern Australia. I am also inclined to believe there was a strong to violent tornado that day (otherwise everyone wouldn't be talking about this day would they?). I would like to see the BoM report, is it publicly available?
Besides a lot of trees and a tractor. it doesn't sound like it hit much. Throwing a two ton tractor 100 m is certainly impressive. Would that alone suggest that it was an F5? What was the extent of the tree damage? Just large branches snapped or were trees debarked?
I whole lot more questions than answers.
-
Thanks Jimmy and Michael for your replys,
I wasn't aware when Australia was rating tornados, I assumed they may have estimated ratings on the older ones based on old reports and photos?
I was thinking the same thing Michael about the two ton tractor sounds like they could get a pretty good estimate on the winds speed from that alone. Surely someone took photos of the forest damage and we would know if large trees were ripped from the ground say? Was the tractor report in the official review? I really wish it was online.
Don't get me wrong I do beleive there was a large and probably violent tornado this day, just hoping for more information :)
-
"The Bulahdelah Tornado was an intense tornado which occurred near the town of Bulahdelah (100 kilometres (62.1 mi) north-northeast of Newcastle), New South Wales on 1 January 1970, and is thought to be the most destructive tornado ever documented in Australia.[1] It is thought to be least F4 or F5 on the Fujita scale however no official rating has been made public.[2][3]
How acurate do you beleive this information to be?
The synoptic charts posted above are impressive to say the least. How often would a setup like this or similar occur in Australia?
It is interesting that they state this, I thought the Bucca tornado rated F4 was the supposed to be the most powerful.
BoM states
The most intense tornado recorded in Australia - with a Fujita rating of F4 - occurred at Bucca, west of Bundaberg (Queensland), on 29 November 1992. The intensity of the winds created freak effects, such as embedding a picture frame in the wall of a room. Hail the size of cricket balls accompanied the storm.
So if the Bulahdelah Tornado 22 years earlier was supposed to be F4-F5 I would have thought along the lines that maybe BoM would have stated it to be equal or stronger than the 1992 Bucca tornado or vice versa. Its interesting. Would be good to have more info. :)
Reference
http://www.bom.gov.au/climate/environ/tornadoes.shtml (http://www.bom.gov.au/climate/environ/tornadoes.shtml)
http://en.wikipedia.org/wiki/1992_Queensland_storms (http://en.wikipedia.org/wiki/1992_Queensland_storms)
http://www.bsch.au.com/severewx/index.shtml (http://www.bsch.au.com/severewx/index.shtml)
-
Listen,
With a path width of 1 mile you would almost guarantee it is a violent tornado. I have the report but there may be issues for it to be placed online. I will see if it is allowable. You can probably go to their NSW Bureau archives and ask for the report. I was also lucky to have the mapped path itself photocopied.
Regards,
Jimmy Deguara
-
Jimmy,
No doubt, if the tornado had a path width of 1 mile it must of been a very strong tornado. I suppose what Enak is getting at, all of the information on the internet is second hand.
-
It would be without a doubt Australia's most destructive tornado to date that we know of. Just a pity that BoM does not use it as a guide to severity etc in rating tornadoes in Australia, but I suppose that is due to the fact of what Jimmy stated in a previous post " Seriously, there was a report on the tornado from the Bureau but until the 1990's. Neverthless, the Bureau has not really rated tornadoes until the 1989 Elsmore, NSW tornado to my knowledge."
(I am also curious to know if they have ever rated the Lennox Head tornado from last year, which is another subject.)
Just digging up some links to see what I could find. It is interesting that many sites have the Bulahdelah Tornado in its top 10 of the worlds most destructive tornadoes.
http://watchmojo.com/top-10/geography/ (http://watchmojo.com/top-10/geography/)
http://scienceray.com/earth-sciences/meteorology/10-most-destructive-tornadoes-from-around-the-world/3/ (http://scienceray.com/earth-sciences/meteorology/10-most-destructive-tornadoes-from-around-the-world/3/)
http://www.islandnet.com/~see/weather/storm/tornadoes-aunzea.htm (http://www.islandnet.com/~see/weather/storm/tornadoes-aunzea.htm)
Colin
-
On slightly another tangent, the difference between Australia (BOM) and the United States (NWS) is that all tornadoes are investigated and rated in the US.
The description from eyewitness of the Bulahdelah tornado refer to rapidly turbulent scud action and low bases. Giant hail was reported that would indicate supercells on this day with smashed windows around Newcastle if I recall and the Mid North Coast.
Regards,
Jimmy Deguara
-
The Bulahdelah tornado report written by B.W. Shanahan at the Bureau of Meteorology is now online.
---> PDF link (http://australiasevereweather.com/storm_news/1970/bulahdelah_tornado_report.pdf)
An interesting read. 55 knots from the NNE at 850 from the Coffs Harbour sounding - not bad lol
Plug a bit more boundary layer moisture into that 9am plot and you'd end up with a rather high CAPE figure.
David Croan replied in an email:
Definitely Michael, I'd say richer moisture would, given those 22 degree dewpoints at noon near Taree, would have advected down so the 16 dewpoint at noon is off. From the model there is not a great deal of 500mb cooling between 0 and 6z, not sure how accurate that is, but the very strong CAP was breached so something changed through the day in addition to just heating. Very dynamic system, those winds 3pm at Coffs ...wow --0-3 SREH would have been high end, and presume 0-1 km too if we had that information.
It seems Australia is a tipping point with these sorts of systems. We have had nothing really like this in the last 13 years, in fact it is getting horribly boring here as far as chasing. Was the fact that this Brisbane and then Sandon tornadoes occurred soon after just a coincidence, or does it reflect subtle shift in longer term patterns. Always hopeful it will tip back in favour of more intense upper systems with this sort of surface cyclogenesis, in the warm season of course. We must be overdue surely!
then Jimmy Deguara responded:
Yes to me the 850 winds and moisture are the key ingredients to low bases and inflow dominant structure. The upper level cooling would have been in place further west at the least. Nevertheless, so long as you have uplift and some lifting mechanism and great shear we are business.
and Michael Thomas
From what I see, there appears to be some pretty big differences between the wind profiles given in the report versus the reanalysis. In the reanalysis, the 850 mbar winds are in the 20 to 30 knot range over the Northern rivers/mid-North Coast whereas in the report the 850 mbar winds much stronger at Coffs Harbour (55 or 60 knots at 3 pm?). I also suspect that the LI's were considerably lower than shown in the reanalysis given that dew points were in 20 to 22 C range with 500 mbar temps around -12 to -14C. How would you rate this outbreak to a classic US setup (with the limited information available)?
-
I will add a few things here. From what I understand, the temperature/dew point at Taree was 26/22 at 1200 EST. Taking a surface-based parcel of 26/22 from the surface and lifting to 500 mbar gives a temperature of -4/-5. The 500 mbar temperature on the Williamtown sounding was -13. Therefore, a rough estimate of the surface-based lifted index (LI) would be around -9/-8. Using a surface-based parcel instead of a mixed-layer parcel usually gives an overestimation of the instability. However, given the direction of the lower-level winds in the afternoon and the observation of scud cloud around the time of the Bulahdelah tornado I would think that moisture would have been quite “deep” in the afternoon. Also, if the observation of 26/22 was taken at midday then there may have been some further heating during the afternoon.
Taking a look at the upper wind profiles from Williamtown and Coffs Harbour in the afternoon, a couple of things are quite interesting. At Coffs Harbour, the lower-level winds are extremely strong and turn from NNE to NW. This would give an enlarged hodograph with strong anticlockwise turning favouring left-moving supercells. The only flaw with the Coffs Harbour upper-level wind profile is the relative weakness in the 700 to 500 mbar winds (40 to 45 knots, not much of a flaw really). The wind speed at 500 mbar at Williamtown is very strong at approximately 65 knots. However, the lower-level winds are not as strong as at Coffs Harbour. For example, the 850 mbar wind speed is only 20 knots from the NE (still pretty good in Australian standards). I wonder whether between Coffs Harbour and Williamtown there was a blend between these two upper-level wind profiles giving both strong lower-level and mid-level winds. If so, that would be a near-perfect profile for strong to violent tornadoes given the strong instability and low LCL’s present that day.
-
Ah very fascinating reading thank you for putting this online. This was an incredible event, they even make observations to the setup being exceptional even if this was in the USA. If only we could get one setup a year like this or similar, at least for the purpose of storm chasing. It wouldn't be fun to see a tornado like that go through a town though!
You can actually make out deforestation in the background of the first photo even in that photo copy.
I wonder if the cricket ball hail at Urunga was from the same storm as that which destoyed the house at Frederickton, which is just east of Kempsey, would have loved to chase that storm also.
Now when are we going to get a setup like this again? haha
-
Hi Enak,
This event may have been briefly comparable to a US style tornado in upper scale but probably not a May 3 1999 Oklahoma City or Joplin style event. We are still talking paramaeters being sketchy for the day and I agree with Michael Thomas and David Croan in terms of downplaying the event a slight touch perhaps F3 to F5 range.
I wonder if the cricket ball hail at Urunga was from the same storm as that which destoyed the house at Frederickton, which is just east of Kempsey, would have loved to chase that storm also.
If trajectories on this day were from the NW, then definitely not. I would perhaps suggest there were quite a few supercells on this day.
And yes, such events are quite rare in this country in my opinion. Tornadic events of varying intensities and significance are simply part of the Great Plains climate!
Regards,
Jimmy Deguara
-
Hi Jimmy,
You mention of the parameters being sketchy for the day. What do you feel was lacking in this storm outbreak?
For most of the big storm days in Australia, there always seems to be something missing. Probably fair to say that moderate to high CAPE with strong deep-layer shear is not exactly rare. These conditions are favourable for supercells with very large hail. The low-level shear is however, usually quite weak and LCL's too high which probably explains the lack of tornadic storms.
I thought I would bring up the September 2009 duststorm too since that was quite an interesting event. Here is the Woomera sounding-
http://soundings.bsch.au.com/skew-t.html?source=wyoming&lat=-31.1558&lon=136.8054&gribdate=&month=09&day=21&year=2009&hour=00&window=on (http://soundings.bsch.au.com/skew-t.html?source=wyoming&lat=-31.1558&lon=136.8054&gribdate=&month=09&day=21&year=2009&hour=00&window=on)
The wind profile on this sounding is quite amazing with an 80 knot NW'y at 500 mbar and a 50 knot NNW'ly at 850 mbar. Mid-level lapse rates are also very steep (though the 300 mbar temp is a bit warm in this sounding). The biggest problem though is the low-level moisture. The surface dew points were only in the low teens that day in the warm sector so instead of a tornado outbreak we had a dust storm.
-
I think that point has been raised in the past a few times. We do see the strong shear from time to time - with decent lapse rates, but those setups are typically always bushfire risk days rather than thunderstorms.
-
Michael Thomas,
You mention of the parameters being sketchy for the day. What do you feel was lacking in this storm outbreak?
I think your previous post above cover things well. I meant to suggest that I was confirming the difficulty to gather sufficient information to achieve a sufficient profile for the time the storm occurred. Was there an increase in the windshear profile. Given the dynamics, were the old profiles and 're-analysis accurate' for so long ago given the lack of data.
I guess what I look for are:
- instability and steep lapse rates. The delta H7-H5 temperature difference > 19C is a rule of thumb for violent tornadoes. Was this the case on this day?
- inflow - one would require to know the pre-storm environment but at least the low level profile was favourably directional
- mid-level moisture profile being dry to enhance clean structure and less upper level loading in terms of precipitation. This should overly deep moisture to 700hPa. Together, with upper level windshear can lead to classic supercell profiles.
- existance of boundaries can assist and this region particularly further south extending to the region west of Bulahdelah have natural boundaries. Were there other outflow boundaries on the day
- upper trough short wave passing through to break a lower level cap
Seriosuly though, the lower level wind shear is the most common missing ingredient that differs between the US and Australia regularly. I feel that deep moisture can also be an issue - the lack of dryline dynamics also tends to be present here.
Whenever we have had ingredients in place, tornadoes occur. Population density or not, someone sees a tornado under the intense storms on the day.
Regards,
Jimmy Deguara