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Aussie (& S-Hemisphere) Cyclone Action 2010-2011

HurricaneJosh

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HurricaneJosh

HurricaneJosh

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Hey, guys! Just as the Atlantic season winds down, Australia's tropical cyclone season has started-- as of 01 November! :thumbsup:

As I did previous years, I'm starting this thread so I have a single place to blog about Aussie action without spamming the board. :D So I'm not talking to myself in this thread for the next six months, here's a quick primer on cyclones Down Under-- a reference source for those of you who want to get a basic lay of the land. (This info is reproduced from the previous years' threads because it's still useful!)

Geography

Here are the basic land areas and water bodies:

post-19-0-16091000-1289497096.png

Land

A large portion of Australia's coastline is threatened by cyclones. Since this is the S Hemisphere, it's like going through the looking glass-- meaning the tropics are to the N and therefore Australia's cyclone country is the N coast. This is actually a tremendous stretch of coastline that spans three states/territories:

* Queensland (QLD) (on the E)

* Northern Territory (NT) (in the middle)

* Western Australia (WA) (on the W)

Most of Australia's population is concentrated in the major cities in the SE-- Brisbane, Sydney, Melbourne, etc.-- and therefore Australia's cyclone country (up N) is mostly very sparsely populated. This means that intense cyclones often make landfall-- particularly in Western Australia-- without causing much damage.

Water

Like Mexico-- and unlike the USA-- Australia is threatened by cyclones from two oceans: the South Pacific to the E and the Indian to the W.

These two oceans are divided into several smaller bodies of water-- most of which are shallow, warm, and game for big cyclones:

The South Pacific (to the E) includes:

*
Coral Sea
-- along the E coast of Queensland

*
Gulf of Carpentaria
-- between Queensland and the Northern Territory

*
Arafura Sea
-- to the N of the Northern Territory

The Indian Ocean (to the W) includes:

*
Timor Sea
-- between Indonesia & Australia

*
Joseph Bonaparte Gulf
-- between the Northern Territory & Western Australia

Warning System

Australia's Bureau of Meteorology (BoM) handles cyclone warnings via its offices in the capital cities of each state/territory:

* BoM Queensland (QLD): Brisbane

* BoM Northern Territory (NT): Darwin

* BoM Western Australia (WA): Perth

Each BoM office has jurisdiction over its own region (including the adjacent waters), and when a cyclone passes from one region to the next, the responsibility for issuing advices (advisories) passes from one office to the next. Here's the regional breakdown (note that Eastern = Queensland):

post-19-0-53795300-1289497118.png

The different territories and jurisdictions means there's no convenient "one-stop shop" (like our National Hurricane Center) for tracking Aussie cyclones. (Grrrrr. :P) However, the BoM simplified their Website information architecture a couple of years ago, so now there's at least one convenient URL from which you can access the different regional warnings: http://www.bom.gov.au/weather/cyclone/.

All of this aside, the USA's Joint Typhoon Warning Center (JTWC) also covers the Aussie region, and they're a good secondary info source, although-- as discussed in other threads-- the JTWC tends to go a bit high with intensity estimates.

Tracking

If you feel inclined, here's the BoM's handy cyclone tracking map for the waters around Western Australia and the Northern Territory: http://www.bom.gov.a...racking_map.pdf B)

Here's one for the entire N coast of the continent, including Queensland-- Australia's entire cyclone zone: http://www.bom.gov.a...let/plotmap.pdf

Cyclone Intensity

In public advices, the BoM indicates cyclone intensity by max gusts-- not sustained (1-min) wind like our NHC. (However, technical discussions will express a sustained wind-- but note that it's a 10-min wind, not a 1-min wind like ours. The conversion factor-- to change a 10-min wind to a 1-min wind-- is ~1.15.) Also, note that for public advices, the Aussies use km/hr-- not mph like we do.

Aussie Intensity Scale

The Aussies have their own cyclone intensity scale-- as follows:

Cat 1 = max gusts: <125 km/h (<68 kt) -- max sustained (10-min): 63-88 km/hr (34-47 kt)

Cat 2 = max gusts: 125-169 km/h (68-91 kt) -- max sustained (10-min): 89-117 km/hr (48-63 kt)

Cat 3 = max gusts: 170-224 km/h (92-121 kt) -- max sustained (10-min): 118-159 km/hr (64-85 kt)

Cat 4 = max gusts: 225-279 km/h (122-151 kt) -- max sustained (10-min): 160-199 km/hr (86-107 kt)

Cat 5 = max gusts: >279 km/h (>151 kt) -- max sustained (10-min): >199 km/hr (>107 kt)

Aussie Intensity Scale vs. American Intensity Scale

How does the Aussie scale (AUS) compare to our Saffir-Simpson scale (USA)? It has five levels, but otherwise it's quite different! Here's a side-by-side comparison with ours:

Cat 1 AUS = tropical storm USA

Cat 2 AUS = tropical storm thru low-end/midrange Cat 1 USA

Cat 3 AUS = high-end Cat 1 thru low-end Cat 3 USA

Cat 4 AUS = midrange Cat 3 thru low-end Cat 4 USA

Cat 5 AUS = midrange Cat 4+ USA

Anything Cat 3 AUS and above is described as a "Severe Tropical Cyclone"-- so, while it sounds dramatic, this label could be (and is) applied to what we would call a strong Cat 1 'cane in the USA. :P

Here's an excellent graphic from the BoM's FAQs which illustrates the relationship between the Aussie and American intensity scales:

post-19-0-51005800-1289497132.png

______

OK-- there's your handy reference source for tracking Aussie cyclones! Who's game? :sun:

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AmyB

AmyB

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Hey, guys! Just as the Atlantic season winds down, Australia's tropical cyclone season has started-- as of 01 November! :thumbsup:

OK-- there's your handy reference source for tracking Aussie cyclones! Who's game? :sun:

I didn't know you had all this info in one "handy reference" all this time..

Just one question.. who's going to migrate that Aussie fella over to here? Is he going to be notified?

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HurricaneJosh

HurricaneJosh

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Josh,

Nice write up. How far south can the cyclones go? Is it just the shaded area inside the BoM?

Hey, thanks-- and nice to see you here! :)

Cyclone can occasionally get further S than that shaded area-- but as with 'canes moving N into the N Atlantic and Canadian Maritimes, they're transitioning by that point, meaning they're not as strong and not pure-tropical cyclones anymore.

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MJW155

MJW155

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Hey, thanks-- and nice to see you here! :)

Cyclone can occasionally get further S than that shaded area-- but as with 'canes moving N into the N Atlantic and Canadian Maritimes, they're transitioning by that point, meaning they're not as strong and not pure-tropical cyclones anymore.

Cool. If you ever get a chance read In A Sunburned Country by Bill Bryson. He spends the summer in Austrailia and talks about the cyclone that basically destroyed Darwin on Christmas Eve. I think it was Cyclone Tracy. Pretty good book actually.

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HurricaneJosh

HurricaneJosh

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Cool. If you ever get a chance read In A Sunburned Country by Bill Bryson. He spends the summer in Austrailia and talks about the cyclone that basically destroyed Darwin on Christmas Eve. I think it was Cyclone Tracy. Pretty good book actually.

Cool-- thanks for the recommendation. I will look for it. I am interested in the history there, as I plan to chase Down Under at some point.

P.S. Yep, Tracy was the cyclone that demolished Darwin on Christmas Eve in 1974. It's Australia's Camille.

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HurricaneJosh

HurricaneJosh

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Thanks for posting that, kush. If I remember correctly, the black dots are cyclone landfalls and the red dots are severe cyclone landfalls... Is that right?

Anyhoo, y'all can see that Western Australia-- especially the Pilbara coast-- is the sweet spot for intense landfalls. It's like Australia's version of the E coast of FL or E coast of the Yucatan. Fortunately for them, the region is sparsely populated, with only a few towns over 10K people: Port Hedland, Karratha, etc.

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k***

k***

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Thanks for posting that, kush. If I remember correctly, the black dots are cyclone landfalls and the red dots are severe cyclone landfalls... Is that right?

Anyhoo, y'all can see that Western Australia-- especially the Pilbara coast-- is the sweet spot for intense landfalls. It's like Australia's version of the E coast of FL or E coast of the Yucatan. Fortunately for them, the region is sparsely populated, with only a few towns over 10K people: Port Hedland, Karratha, etc.

yeah, black is non severe and red is severe

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HurricaneJosh

HurricaneJosh

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The Aussie season has just started, and there are no interesting features yet in the tropical waters around the continent-- but as kush posted above, the seasonal forecast from the BoM is very bullish: http://www.bom.gov.au/climate/ahead/tc.shtml

There is particular concern for Western Australia, for which the BoM warns: "This season there is a higher-than-normal risk of a pre-Christmas cyclone and with the cyclone season rapidly approaching it is important that residents start preparations immediately": http://www.bom.gov.au/wa/cyclone/seasonal/

Like the USA, Australia has gotten off relatively easy the last couple of seasons-- after some very damaging strikes in the mid-2000s (Larry 2006, George 2007, etc.). The 2010-2011 season just might be the game changer.

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kwt

kwt

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Just had a look at those numbers Josh and they are very impressive indeed, 20-22 is expected.

Saying that exactly where would it rank roughly if it came off on the all time list?

I'm not quite so sure given I'm not into Austrailia's TC quite as much as say the Atlantic...

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SnowGoose69

SnowGoose69

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Just had a look at those numbers Josh and they are very impressive indeed, 20-22 is expected.

Saying that exactly where would it rank roughly if it came off on the all time list?

I'm not quite so sure given I'm not into Austrailia's TC quite as much as say the Atlantic...

I think 97-98 was the most active year ever in the Southern Pacific (25-30 storms I believe) but I'm not so sure this actually encompassed the actual Australian region since El Ninos generally produce more activity in the western South IO and "eastern" South Pac while the Ninas go vice versa in the eastern South IO and western South Pac. Unisys may have archived charts for the southern pacific

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k***

k***

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I think 97-98 was the most active year ever in the Southern Pacific (25-30 storms I believe) but I'm not so sure this actually encompassed the actual Australian region since El Ninos generally produce more activity in the western South IO and "eastern" South Pac while the Ninas go vice versa in the eastern South IO and western South Pac. Unisys may have archived charts for the southern pacific

:wub: 97-98

2 active cat 5's on the same day

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HurricaneJosh

HurricaneJosh

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Just had a look at those numbers Josh and they are very impressive indeed, 20-22 is expected.

Saying that exactly where would it rank roughly if it came off on the all time list?

I'm not quite so sure given I'm not into Austrailia's TC quite as much as say the Atlantic...

That's a good question-- I'm not sure what their record is for busiest season, and I couldn't find it from a quick search on the BoM site. However, here's a chart showing annual totals. Keep in mind that each Aussie season straddles two years. For example, right now we're in the 2010-2011 season.

Interestingly, this chart doesn't suggest that 1997-1998 was their busiest season ever, as SnowGoose has suggested. Weird.

post-19-0-95264500-1289874134.png

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HurricaneJosh

HurricaneJosh

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Maybe Brisbane will finally get their big one

Which is sort of like suggesting that NH or ME might get their big one. :D

I don't think the cyclone threat to Brisbane even equals that of S New England, as I can find very few instances of what we would call a hurricane directly impacting the city.

The Gold Coast Cyclone of February 1954 is apparently the most significant impact in that region-- a possible Cat 2 or 3 (on our scale) that crossed the coast just S of Brisbane. Dinah 1967 could have been a big hit but recurved just offshore. Brisbane has had some flooding events from weak or transitioning systems as well-- a la Wanda 1974 and a cyclone in 1893.

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PSUBlizzicane2007

PSUBlizzicane2007

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Which is sort of like suggesting that NH or ME might get their big one. :D

I don't think the cyclone threat to Brisbane even equals that of S New England, as I can find very few instances of what we would call a strong hurricane directly impacting the city.

The Gold Coast Cyclone of February 1954 is apparently the most significant impact in that region-- a possible Cat 2 or 3 (on our scale) that crossed the coast just S of Brisbane. Dinah 1967 could have been a big hit but recurved just offshore. Brisbane has had some flooding events from weak or transitioning systems as well-- a la Wanda 1974 and a cyclone in 1893.

They'll get one eventually when the pattern sets up correctly...it's not THAT unlikely that they see an Australian Cat 4 that has weakened from a 5.

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HurricaneJosh

HurricaneJosh

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They'll get one eventually when the pattern sets up correctly...it's not THAT unlikely that they see an Australian Cat 4 that has weakened from a 5.

Well, since there's no recorded instance of that happening-- and I can find only one instance of a Cat 3 AUS hitting the region (Gold Coast Cyclone 1954)-- it seems pretty unlikely to me. Besides being so far S, the city's not even well-situated: it's on an E-facing coast, making it like DE or NJ-- parallel to most cyclone tracks. Dinah 1967 moved parallel to the coast and missed.

A Cat-4 AUS impact in that area is a 200-year event, at most-- maybe more like 500-year.

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