Cyclone Yasi

[EastCoastLow]

Well, the trough extending south east from the remains of Yasi is wreaking havoc. We had a severe rain event here in Canberra yesterday afternoon and drizzle overnight, we has 50mm of rain in 20 mins at work (an estimate) in the form of a long squall line of severe storms, which for this time of year, in this region is unheard of. Enough to flood out our work with 45cm of free running water.

A note on the photos of Tracy you are comparing cyclones to. Please remember that Darwin was an outpost town in 1974 and the building construction was VERY light. We're talking fibro sheeting and hastily built, standard pattern housing. I'm not saying Tracy was a weak storm, just to consider that when basing damage estimates on photos.

This is an interesting graph, taken from the BOM's Tsunami DART buoy. I'm impressed by how much SST dropped:

[Scott747]

A note on the photos of Tracy you are comparing cyclones to. Please remember that Darwin was an outpost town in 1974 and the building construction was VERY light. We're talking fibro sheeting and hastily built, standard pattern housing. I'm not saying Tracy was a weak storm, just to consider that when basing damage estimates on photos.

We had a nice Tracy thread at the old board and took note of the shoddy construction in Darwin that no doubt made the images look even worse. Some of the heavy damage that was seen to the trees was due to much of the flying debris.

[k***]

"south of innisfail"

check out this site with a slider thing that allows you to scroll between more before and after photos...the last one of dunk island is RIDICULOUS...especially the completely denuded hill on the right side of the photo.

http://www.couriermail.com.au/news/queensland/yasi-damage-revealed-in-photo-slider-before-after-images-of-tully-cardwell-and-hinchinbrook/story-e6freoof-1226000394648

Static before-and-afters taken from a similar vantage point:

Finally, those buildings on Dunk that seemed to hold up well were built to withstand a Cat 5 according to this article.

[Scott747]

Seen any pictures from Bedarra island?

[k***]

Seen any pictures from Bedarra island?

None. I've been looking too.

Dunk is clearly ground zero--nothing even comes close so far.

[k***]

I am also waiting to see the aftermath on Willis Island.

[Scott747]

"south of innisfail"

check out this site with a slider thing that allows you to scroll between more before and after photos...the last one of dunk island is RIDICULOUS...especially the completely denuded hill on the right side of the photo.

http://www.courierma...f-1226000394648

Static before-and-afters taken from a similar vantage point:

Finally, those buildings on Dunk that seemed to hold up well were built to withstand a Cat 5 according to this article.

The trees are impressive. Would love to see some low level aerial footage of both islands.

[AussieStormGirl]

Hi Josh

Just wanted to let you know that all is OK over here. I'm so thankful that we dodged that bullet....bloody horrible. Have to try and get down there in the next day or two as we have to get through Cardwell/Tully to get to Townsville.

Anyway read an article warning there could be more to come...see below. Looks like you guys may have more opportunities to follow further storms....but we'll wait and see what happens.

“This La Nina pattern is by far the most intense pattern witnessed anywhere in the world. There is a least still three months of risk of more significant rainfall and significant cyclonic events,” Prof. Stone said.

As reported in The Chronicle in October, the La Nina weather pattern was still very prominent and the risk of more destructive weather events was highly probable.

“The basic underlaying problem that is causing all these extreme weather patterns is still very much with us.

“The Coral Sea is still excessively hot and we will definitely see more excess rain across Queensland and Toowoomba in the coming months,” Prof. Stone said.

Prof. Stone said that the chances of more cyclones the size and scale witnessed in North Queensland last night is definitely a reality that we must face.

“Cyclone Yasi is one of the biggest and most intense weather patterns that has ever been seen anywhere in the world and we are in cyclone season so, combined with the intense La Nina, there is the definite risk that more will follow,” Prof. Stone said.

[A-L-E-X]

From our perspective, it's basically the start of August there (right when tropical activity really starts to ramp up), so the peak of TC season should be in March there and usually the tropical season doesnt start tailing off here until the end of October, which would be April over there... so it's definitely just the beginning of the really active part of the TC season.

[Normandy]

Gotta say that the Dunk Island picture is pretty stunning. There might be some argument there for 135 kt or borderline Cat 5. Looks just like Majahual after Dean passed.

[k***]

Gotta say that the Dunk Island picture is pretty stunning. There might be some argument there for 135 kt or borderline Cat 5. Looks just like Majahual after Dean passed.

Yeah that is definitely the best photo showing damage so far.

[wxmx]

Denuded trees are telling, especially the palms... that's even easily seen in the trees in the background. The pool was obviously destroyed by the surge. Yep, a high end 4 at least...the relatively high central pressure for a rather large cyclone is probably the only thing against a low end 5, since between a 135 vs a 140 there should be no difference in destruction level.

[Ed Lizard]

Well South, in MacKay, but closest I can find on U-Tube.

[battlebrick]

Not giving up.

[HurricaneJosh]

Denuded trees are telling, especially the palms... that's even easily seen in the trees in the background. The pool was obviously destroyed by the surge. Yep, a high end 4 at least...the relatively high central pressure for a rather large cyclone is probably the only thing against a low end 5, since between a 135 vs a 140 there should be no difference in destruction level.

I think the damage is impressive, and I remain comfortable with the blended (BoM/JTWC) value of 130 kt. I would expect to see this sort of damage from Ground Zero of an upper-end USA Cat 4.

The tree denuding of course grabs the attention, but one thing I'd like to point out is that this was a very large cyclone, so the winds had a lot of time to really work these locations-- and longer-duration winds means more time to tear off foliage little by little. A cyclone like Charley (tiny and fast-moving) only pounded its ground-zero locations with hurricane winds for an hour or two, probably. An EF4 tornado does it in about 45 seconds.

So... I still do not think this was a USA Cat 5 or even flirting with that intensity. I am not seeing any damage which screams "Cat 5", nor would that combination of central pressure (929 mb), wind radii (enormous), and intensity trend (flat) support a conclusion of 140+ kt.

A solid USA Cat 4-- not higher. Thx.

[k***]

I see the myth of steady-state yasi is alive and well.

[HurricaneJosh]

I see the myth of steady-state yasi is alive and well.

If you're going to dig at my viewpoint, support yours with something.

The BoM's own analysis showed no intensification leading up to landfall, and the landfall central pressure (929 mb) compared with the Willis Island pressure (~937 mb) shows only a modest drop over the 15 hrs or so between those locations. So if it was strengthening-- and it might have been-- it was strengthening slowly. It definitely wasn't bombing out-- not in the way that would cause a spectacular deviation from the standard wind/pressure relationship. So for the purposes of this discussion Re: landfall intensity, I count it as "steady-state".

Either way, 929 mb with those wind radii wouldn't support Cat-5 winds.

[Ed Lizard]

JB has used weakening/strengthening/steady state, arguing as much as a Cat difference in affect for the same RMW and barometric pressure. I don't know how scientific that is, but, intuitively, a strengthening storm would probably have more intense convection, and therefore mix winds down more effectively.

Opposite end, a strong storm moving over markedly cooler waters, and a fairly stable near surface layer cooled by the cold water (or the East Pac storms you know will soon be remnant swirls as they start ingesting strato-cu) don't mix down winds very well at all. Or a storm moving into the death dagger of shear. If it can't crank strong storms, how can it be expected to mix down winds. If it isn't mixing them down, then it is a straight pressure differential over area. Again, intuitively, that would seem to be more limiting for gusts than sustained winds, but then gusts do much/most of the wind damage.

Its like SPC wind probs for strong but elevated storms. Not very high.

[HurricaneJosh]

JB has used weakening/strengthening/steady state, arguing as much as a Cat difference in affect for the same RMW and barometric pressure. I don't know how scientific that is, but, intuitively, a strengthening storm would probably have more intense convection, and therefore mix winds down more effectively.

Opposite end, a strong storm moving over markedly cooler waters, and a fairly stable near surface layer cooled by the cold water (or the East Pac storms you know will soon be remnant swirls as they start ingesting strato-cu) don't mix down winds very well at all. Or a storm moving into the death dagger of shear. If it can't crank strong storms, how can it be expected to mix down winds. If it isn't mixing them down, then it is a straight pressure differential over area. Again, intuitively, that would seem to be more limiting for gusts than sustained winds, but then gusts do much/most of the wind damage.

Its like SPC wind probs for strong but elevated storms. Not very high.

Agreed Re: the how strengthening/weakening state affects the mixing down to the surface-- and that why we're talking about this factor. (This is generally accepted-- not a JB thing.) My point is that Yasi wasn't bombing out in a way that would augment the winds like that.

P.S. I don't totally agree with your statement "gusts do much/most of the wind damage". A good portion of the damage is a function of the duration of the winds-- not just the extreme, peak values.

[k***]

If you're going to dig at my viewpoint, support yours with something.

The BoM's own analysis showed no intensification leading up to landfall, and the landfall central pressure (929 mb) compared with the Willis Island pressure (~937 mb) shows only a modest drop over the 15 hrs or so between those locations. So if it was strengthening-- and it might have been-- it was strengthening slowly. It definitely wasn't bombing out-- not in the way that would cause a spectacular deviation from the standard wind/pressure relationship. So for the purposes of this discussion Re: landfall intensity, I count it as "steady-state".

Either way, 929 mb with those wind radii wouldn't support Cat-5 winds.

There were no in-situ observations for the BOM to go off of...satellite trends were for a strengthening system. Even if in the last two hours or so it slowed up a bit, the ten before that showed significant strengthening--the eye dried out and warmed at a crazy rate, symmetry improved, deep convection increased etc, T numbers were up, etc. I guess I just don't see how you can say it was "steady state" unless you compress the time you are making that observation down to something really small, like <3 hours. Because up until then Yasi was definitely strengthening, regardless of what official BOM advisories say.

Unrelated, but why are you so convinced that it was 929 and not possibly lower? Have you verified that the measured pressure was dead-center in the eye? We had a conversation during the Willis Island passage about how radically these things change over the course of a few miles. What if the storm was 924 instead of 929? You mention the standard wind-pressure relationship...can you tell me what that is for the Coral Sea? Because the only ones I am familiar with are ones for the NW pacific, EPAC, and Atlantic.

[am19psu]

There were no in-situ observations for the BOM to go off of...satellite trends were for a strengthening system. Even if in the last two hours or so it slowed up a bit, the ten before that showed significant strengthening--the eye dried out and warmed at a crazy rate, symmetry improved, deep convection increased etc, T numbers were up, etc. I guess I just don't see how you can say it was "steady state" unless you compress the time you are making that observation down to something really small, like <3 hours. Because up until then Yasi was definitely strengthening, regardless of what official BOM advisories say.

I strongly agree with this and argued it earlier in the week. It was not bombing, but was definitely intensifying.

[k***]

I strongly agree with this and argued it earlier in the week. It was not bombing, but was definitely intensifying.

I went back a few pages and the MW shots josh posted have an absolutely classic look to them...hard to imagine a better MW for a storm so close to landfall. The shots that bronxx posted near landfall as well are telling--the WV image is insane--you could have lit a forest fire in that eye it was so dry.

[k***]

If I ever became a billionaire I'd immediately create an endowment that would perpetually fund a global recon strikeforce. This whole argument could be ended if we had quality obs.

[bronxx]

You tubes: these are two seperate videos.

[HurricaneJosh]

There were no in-situ observations for the BOM to go off of...satellite trends were for a strengthening system. Even if in the last two hours or so it slowed up a bit, the ten before that showed significant strengthening--the eye dried out and warmed at a crazy rate, symmetry improved, deep convection increased etc, T numbers were up, etc. I guess I just don't see how you can say it was "steady state" unless you compress the time you are making that observation down to something really small, like <3 hours. Because up until then Yasi was definitely strengthening, regardless of what official BOM advisories say.

I felt the organization improved a little leading up to landfall, but not in a way that suggested it was bombing out and that would cause major deviation from a standard W/P relationship. Maybe Adam can weigh in here.

Also, I think the 3 hrs makes a difference. I think it really matters whether it was bombing as it crossed the coast.

Unrelated, but why are you so convinced that it was 929 and not possibly lower? Have you verified that the measured pressure was dead-center in the eye? We had a conversation during the Willis Island passage about how radically these things change over the course of a few miles. What if the storm was 924 instead of 929? You mention the standard wind-pressure relationship...can you tell me what that is for the Coral Sea? Because the only ones I am familiar with are ones for the NW pacific, EPAC, and Atlantic.

Re: the pressures... 930 mb was observed at Clump Point, in Mission Beach, exactly at the landfall point, and 929 mb was observed at Tully-- a couple of mi inland, exactly in the path of the center. These reading corroborate nicely and I don't see why we should assume the pressure was lower. The landfall point was well-sampled.

Brown et al indicate a wind of 131 kt for a steady-state cyclone with a pressure of 929 mb deep in the tropics in the NATL-- a couple kt higher if it's strengthening. That is before any adjustments are made for size. This cyclone was very large, so the orthodox approach here would be to "penalize", whereas for a microcane like Tracy, you would add. Keep in mind, the NATL generally has higher winds for the same pressure compared with other basins-- so, for example, a WPAC W/P standard would yield a lower wind for 929 mb. So I feel like I'm being generous to use the NATL table (although Steve suggested it might not be so far off to use it this year, because of prevailing conditions).

And, again, I want to point out that my estimate (130 kt) is in line with a blended value from experts at the BoM and the JTWC who were also analyzing the satellite imagery, and who concluded 110 kt (10-min) and 135 kt (1-min), respectively.

[HurricaneJosh]

Just bumping this post from Steve, suggesting why the NATL W/P relationships might be OK to use for this instance.

A couple of points to make about wind/pressure relationships. First off with a La Niña, you are going to have pressures in SPAC somewhat higher than climo which brings up a second point. JTWC in their assessment of STY Paka when it passed Guam noted that when pressure are higher than climo in WPAC (or because of normally seasonal higher pressures) that the WPAC w/p relationship didn't work well and that the ATL w/r one was better under those conditions. This brings up Megi-the w/r relationship for JTWC for a storm with 890 mb pressure is around 140 kt yet Megi clearly had 155 kt (if not more as measured) so that particular w/p relationship may not really work out that well even in WPAC.

Steve

[am19psu]

I'm ok with the 130 kt estimate, I'm just picking nits about your claim that it was steady state. I'm of the opinion it was modestly intensifying at landfall, mainly due to the warming/drying trend within the eye. Cold convection was already at the tropopause for about 24 hrs beforehand, so that's no help. Without recon, the best judges of intensity are Dvorak (which was intensifying in the last 6 hours before landfall due to the warming eye) and SATCON (which gave no info in the 6hrs before landfall).

[HurricaneJosh]

I'm ok with the 130 kt estimate, I'm just picking nits about your claim that it was steady state. I'm of the opinion it was modestly intensifying at landfall, mainly due to the warming/drying trend within the eye. Cold convection was already at the tropopause for about 24 hrs beforehand, so that's no help. Without recon, the best judges of intensity are Dvorak (which was intensifying in the last 6 hours before landfall due to the warming eye) and SATCON (which gave no info in the 6hrs before landfall).

OK, I gotcha. I agree with your viewpoint, and as I mentioned above, I can accept it was slowly strengthening. In that case, though, I still think my general logic applies, as we can agree it wasn't bombing out in a way that would cause a crazy deviation from the standard W/P relationship-- a la King 1950, Celia 1970, Andrew 1992, and Charley 2004. (I should point out that these cyclones' max winds were also helped by very small RMWs.)

[Ed Lizard]

If I ever became a billionaire I'd immediately create an endowment that would perpetually fund a global recon strikeforce. This whole argument could be ended if we had quality obs.

Australia isn't the Philippines or Bangladesh. If they can afford F-18 Super Hornets they can (just checked Wiki) afford to modify two of their 16 Hercules transports to weather recon missions.

I have thought the same thing about Japan...

[k***]

I felt the organization improved a little leading up to landfall, but not in a way that suggested it was bombing out and that would cause major deviation from a standard W/P relationship. Maybe Adam can weigh in here.

Also, I think the 3 hrs makes a difference. I think it really matters whether it was bombing as it crossed the coast.

It wasn't steady state. Adam has already weighed in twice. Plus, there is no standard w/p relationship, so I am not sure why you keep bringing it up as if it's ironclad fact.

As for the 3 hours part, look at the microwaves you yourself posted--they are classic and really can't be improved upon. Same with the water vapor.

Re: the pressures... 930 mb was observed at Clump Point, in Mission Beach, exactly at the landfall point, and 929 mb was observed at Tully-- a couple of mi inland, exactly in the path of the center. These reading corroborate nicely and I don't see why we should assume the pressure was lower. The landfall point was well-sampled.

Is it normal for place on the coast "exactly at the landfall point" to have higher pressures than those further away and inland?

Brown et al indicate a wind of 131 kt for a steady-state cyclone with a pressure of 929 mb deep in the tropics in the NATL-- a couple kt higher if it's strengthening. That is before any adjustments are made for size. This cyclone was very large, so the orthodox approach here would be to "penalize", whereas for a microcane like Tracy, you would add. Keep in mind, the NATL generally has higher winds for the same pressure compared with other basins-- so, for example, a WPAC W/P standard would yield a lower wind for 929 mb. So I feel like I'm being generous to use the NATL table (although Steve suggested it might not be so far off to use it this year, because of prevailing conditions).

Not the North Atlantic. Why do you feel generous using it? Your conversions here are really just your own subjective massaging.

And, again, I want to point out that my estimate (130 kt) is in line with a blended value from experts at the BoM and the JTWC who were also analyzing the satellite imagery, and who concluded 110 kt (10-min) and 135 kt (1-min), respectively.

At the end of the day we are arguing over maybe 5 knots. I think I feel safer being uncertain about where this sits than declaring based upon other basins WP relationships and a few photos that this was definitely not a 5. I think it very well could have been. Do I have evidence? Only speculative...I'll admit that. But based upon how little of an area really experiences max winds in any landfalling system, it's like finding a needle in a haystack. There could be a strip of jungle south of mission beach that caught the absolute max and we'd have missed it since that's not the type of stuff that makes news accounts.