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Cyclone Yasi


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So, in the immediate aftermath of this huge event, two things stand out for me:

1. SSTs really don't matter that much. Blending the JTWC and BoM estimates yields a landfall intensity of 130 kt-- a high-end Cat 4. A really good upper-air pattern allowed this cyclone to steadily strengthen into a very intense system over really lackluster heat content.

2. The modeling was unbelievable. How far out was this exact scenario modeled? We started talking about it well over a week ago, when the Euro showed a large, intense cyclone hitting Queensland around 03 Feb (tomorrow). There was tight agreement between the models as the cyclone formed and approached, so that the precise landfall point-- a little S of Cairns-- was correctly forecast several days ago. Just amazing. Were the models even that spot on with Dean 2007?

It will be interesting to see the aftermath in the morning-- to get a better idea of exactly what happened and how strong the winds were. I'm thinking we'll see some stripped, denuded trees near and just to the left of the landfall point.

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1. SSTs really don't matter that much. Averaging the JTWC and BoM's intensity estimates yields a landfall intensity of 130 kt-- a high-end Cat 4. A relaly good upper-air pattern allowed this cyclone to steadily strengthened over really lackluster heat content.

This has been proven time and again to me. You need both dynamics and thermodynamics. If shear is virtually nil, you can get RI with SSTs around 27.5. If you have SSTs above 30, you can get RI with as much as 10 kts of shear. But low shear is the necessary condition for RI, imo, and you can't get Cat 4/5s without RI except in rare cases.

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So, in the immediate aftermath of this huge event, two things stand out for me:

1. SSTs really don't matter that much. Blending the JTWC and BoM's estimates yields a landfall intensity of 130 kt-- a high-end Cat 4. A really good upper-air pattern allowed this cyclone to steadily strengthen into a very intense system over really lackluster heat content.

Oy.

I get the gist in context with this particular storm and plenty of others. Let's just not get to carried away...

Maybe 'didn't' would be more appropriate and all will be well.

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This has been proven time and again to me. You need both dynamics and thermodynamics. If shear is virtually nil, you can get RI with SSTs around 27.5. If you have SSTs above 30, you can get RI with as much as 10 kts of shear. But low shear is the necessary condition for RI, imo, and you can't get Cat 4/5s without RI except in rare cases.

We generally have always agreed that upper air conditions are more important overall but without solid and enhanced SST's being available then we're less likely to see a RI cycle.

I don't know how many times over the last years it has taken that pocket of higher grade octane (sst's) to send a storm to another level.

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This has been proven time and again to me. You need both dynamics and thermodynamics. If shear is virtually nil, you can get RI with SSTs around 27.5. If you have SSTs above 30, you can get RI with as much as 10 kts of shear. But low shear is the necessary condition for RI, imo, and you can't get Cat 4/5s without RI except in rare cases.

That makes sense. I shouldn't oversimplify the dynamics, as it really is a combination of factors working together. But I get the impression here that you feel low shear is even more important than heat content (assuming, of course, the SSTs are at least above the minimum hurricane threshold).

Oy.

I get the gist in context with this particular storm and plenty of others. Let's just not get to carried away...

Maybe 'didn't' would be more appropriate and all will be well.

Fair enough. Perhaps that was an overstatement. I think Adam put it better.

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There's definitely a weenie obsession with SSTs as the be-all and end-all - largely, I think, from the emphasis on SSTs in simplistic articles and documentaries on tropical cyclones, largely because it's far simpler to discuss than atmospheric shear.

How many times have you seen the "IT'S GONNA EXPLODE WHEN IT HITS THE (Warm Gulf Waters, the Gulf Stream)!!!!!!" posts....and then it doesn't.

I mean, obviously the SSTs have to meet the minimum criteria for TC development, but I've sort of stopped looking at detailed SST maps; the importance of SST variations, loop currents, whatever seems so massively overwhelmed by things like shear, dry air intrusion, etc.

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We generally have always agreed that upper air conditions are more important overall but without solid and enhanced SST's being available then we're less likely to see a RI cycle.

I don't know how many times over the last years it has taken that pocket of higher grade octane (sst's) to send a storm to another level.

Right, I agree. With very high SST/OHC, you can get RI with less than ideal shear. With shear <5 kts, though, it doesn't appear to me that SSTs do much to control RI. I know Margie Kieper's RI forecasting method doesn't even take into account SSTs (though they are somewhat implicit in the SHIPS RI algorithm).

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Right, I agree. With very high SST/OHC, you can get RI with less than ideal shear. With shear <5 kts, though, it doesn't appear to me that SSTs do much to control RI. I know Margie Kieper's RI forecasting method doesn't even take into account SSTs (though they are somewhat implicit in the SHIPS RI algorithm).

The NGOM and WCARIB are two great places to notice the effects of SST/TCHP.

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Trucking inland. The BoM still has it as a Cat 4 (n their scale), with peak gusts of up to ~125 kt. I've never seen the BoM extend a cyclone warning so far inland.

Winds along the coast still rippin' good. It'll take hours for things to die down in those coastal communities.

Notice a S wobble in the track probably spared Innisfail the worst, although early reports suggest the town still got clobbered pretty hard.

post-19-0-94407900-1296671846.gif

post-19-0-52141500-1296671858.jpg

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Haven't seen anything from the chasers since last night.

http://www.ustream.tv/channel/test222223435432e#utm_campaigne=synclickback&source=http://www.severeweatherchasers.com/index.html&medium=6484768

Sound like from a few posts on the local Aussie forum I read last night that two of them were rather new and that they had either picked up or another more experienced chaser joined them. Maybe Josh has more insight....

Definitely not the type of storm any inexperienced chaser would want to be in or navigate.

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By the way, for posterity, here is the track map from when landfall occurred, showing the approx. coverage of high winds. The advice said:

VERY DESTRUCTIVE winds with gusts up to 290 km/h between Cairns and Ingham and the adjacent ranges will extend inland and gradually weaken.

The VERY DESTRUCTIVE CORE of the cyclone will take up to 4 hours to pass.

Man, that is a pretty long time for the worst conditions to last-- it's usually just an hour or two.

post-19-0-49938300-1296672268.gif

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Haven't seen anything from the chasers since last night.

http://www.ustream.tv/channel/test222223435432e#utm_campaigne=synclickback&source=http://www.severeweatherchasers.com/index.html&medium=6484768

Sound like from a few posts on the local Aussie forum I read last night that two of them were rather new and that they had either picked up or another more experienced chaser joined them. Maybe Josh has more insight....

Definitely not the type of storm any inexperienced chaser would want to be in or navigate.

They set up in Ingham and stayed put. It looks like they missed the eyewall but certainly had hurricane conditions, as Lucinda-- a reporting station close by-- had a couple of hours of winds over 65 kt. They didn't punch the core, but they got some good action.

By the way, they're not complete novices-- I know Orebound chased Ului last year, and maybe other cyclones-- but I do think this might have been his first heavy-duty system.

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I don't know if SATCON will update with a reading prior to landfall, but the ADT was at 7.0. Josh, was this the strongest non-West Pac landfall since Andrew? I can't think of any stronger.

http://cimss.ssec.wisc.edu/tropic2/real-time/adt/11P-list.txt

Dean 2007 hit MX with an intensity of 150 kt-- so it was stronger even than Andrew. And Felix 2007's landfall intensity in NI was 140 kt.

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