How low can a TC go?

[nig&nog]

A few of us had a quick discussion yesterday regarding how far south can a TC travel before it runs out of spin and becomes a low. We have just been watching the one over in WA and we were quite suprised that it lasted so long as a TC before it became a Low. Do any of our MET specialists have any good info that they would like to share, thanks

NIG

[morno]

Think it depends on 2 main things. The sea surface temperature and the amount of wind shear in the upper levels to break it down.

I'd say because it's now so far south, it'd be a combination of both that's breaking it down.

morno

[WannaBeBiggles]

A very simplified explantation.

Cyclones need water of about 26 degrees to form, this gives it the energy they need. If you take this away, either by dropping the temperature of the water or the cyclone hits land, it will loose this energy and start deteriorating.

Pretty sure that's how I remember it from MET anyway

[Cravenmorehead]

I thought once it had a central pressure less than 1000hpa it technically becomes a Tropical Cyclone. Obviously as it tracks south it loses the factors such as warm sea and the notherly winds and moisture that help it form along the monsoon trough. There is no set latitude.

[ForkTailedDrKiller]

I seem to recall that the Nth Island of NZ has been beaten up on a number of occassions by at least the remnants of cyclones that started out in the Coral Sea.

Dr

[MyNameIsIs]

Tropical Cyclone Information for the Australian Region

Check that out, a Cyclone that cuts right thru the middle of Aus back in '95.

Craven, I'm not so sure if "because its less than 1000, it's a cyclone" is quite accurate because you get plenty of low pressure systems with a central pressure lower than 1000 that do not form as a cyclone, I think they just get referred to as a tropical low. However it is probably quite correct to say that you wont have a TC with a central pressure near 1000hpa.


Sea surface temperature is one of the biggest factors to forming and sustaining a TC- as mentioned, above about 26C and you have the right stuff. Shear is also a key part.

BoM site has a lot of info about the hows and whys.


We've got some pretty warm seas this year, so far the season has been quite active- expect a few more before it ends!

Would have been interesting if Bianca crossed as an active cyclone down near Perth. She dropped a bit of water along the Pilbara.

[peuce]

I seem to remember from my Met training that there in NO Australian State that has NOT been hit by a Cyclone. But there again memory sometimes plays silly games

[WannaBeBiggles]

There is no set latitude

Not quite true. Cyclones can't form near the equator due to lack of Coriolis effect. No rotation = not cyclone.

[Monopole]

TC Vance

Play with the date on the link above, and you will see that its not really all that uncommon. 1999, saw TC Vance, cross the coast up near Onslow travel inland through the Goldfields and into the Great Australian Bight. From memory, it spent about 3 days in the bight still catagoized as a TC..

Actually, I just put in a date from 1975 till now and there are about 15 that ended south of the Bight with one, TC Harriot well into the Southern Ocean, and one TC Ned crossing the coast of Perth in 1989.

[Ex FSO GRIFFO]

TC 'Alby' in April '78 was still classed as one if I remember correctly, and it ventured well to the South of Perth, as the following link will show...

Tropical Cyclone Alby

The plot shows it still classed as a cyclone passing 35S - the equivalent of Albany.

We had not long moved into our new house in the Perth suburb of Thornlie, 11nm in from the coast and had a neighbour's vintage Paperbark blown over - right across our power lines, and the power was off for over three days until the authority of the time could reconnect.
Lots of mostly 'minor' damage widespread.

[compressor stall]

Tropical Cyclone Information for the Australian Region

Last 100 years of cyclones.

[Ex FSO GRIFFO]

Hey Mr 'M', not trying to pinch your post, but this link should open OK,

Severe Tropical Cyclone Vance

Cheers

[eocvictim]

Last week there were 14 lows around the antarctic below 1000hp... I don't think you can call them tropical lows if they're in the polars. Interestingly there were 3 active TC's in the Aus region at the time and they were all above the lowest 3 Polar lows.

[MyNameIsIs]

Last week there were 14 lows around the antarctic below 1000hp... I don't think you can call them tropical lows if they're in the polars.

Yeah, I'd probably call them Polar Lows


If it wasn't obvious in my last post, I was referring to lows below 1000 in the regions where cyclones form, not all lows in general. . . .

[The Green Goblin]

I was waiting for the global warming factor to rear its head

[tinpis]

Its becasuse of all the mining in the Pilbara innit Bob?

[eocvictim]

Yes, Yes. There's flooding rain in summer over the better part of the country, its cold, its hot, there have been 10 TC so far this wet season and extensive frontal activity down south, end times approach, everyone into the doomsday bunker.

[Kanga767]

Cyclones can't form near the equator due to lack of Coriolis effect.

Although quite rare, it can happen, as in Tropical storm Vamei in 2001 near Singapore and Typhoon Sarah in 1956. However, it would appear that rotation does not come from the Coriolis effect, so you are half correct, but rather just the right combinations of weather conditions in the 800 to 500 hPa layers and the terrain.


K

[Mr. Hat]

I thought you were talking about Terms and Conditions and was going to direct you to the Tiger/Jetstar/VAustralia/Centrelink websites

[maverick22]

There you go, straight from the BoM website:

A tropical cyclone is defined as a non-frontal low pressure system of synoptic scale developing over warm waters having organised convection and a maximum mean wind speed of 34 knots or greater extending more than half-way around near the centre and persisting for at least six hours.