Cyclone Yasi

[k***]

Not to mention that 5 kts is well within the error bars of any satellite based intensity estimation or P-W estimation...

Yeah, that's the resolution we came to in private

Anyways, back to San Felipe's size...I am pretty confident that it was a big fat monster...

http://harvardforest.fas.harvard.edu/publications/pdfs/boose_ecomonographs_2004.pdf

For example,in the San Felipe storm of 1928, a category 5 hurricane on the Saffir-Simpson scale, winds of hurricane force ($33 m/s) lasted 12–18 hours across much of the island, with peak winds measured at 72 m/s in San Juan (before the anemometer blew apart); rainfall exceeded 640 mm in the higher terrain and some towns near the

center of the storm were practically leveled (Fassig1928); forests at higher elevations were almost completely destroyed (Bates 1930)

look at the amount of F3 damage across the island:

[HurricaneJosh]

kush, check out this very interesting read-- from the "additional notes" Re: the NHC's reanalysis of the San Felipe 1928 hurricane: http://www.aoml.noaa.gov/hrd/hurdat/metadata_1926-30.html#1928_additional

They set the PR landfall intensity at 931 mb/140 kt, but with great reservations. In the end, they based their whole verdict on what appeared to be a reliable surface ob from San Juan Weather Bureau Office-- 139 kt (1-min)!! Honestly, I am extremely skeptical Re: that reading-- I don't buy it. San Juan wasn't even near the landfall point!

Their reservations Re: the 1928 'cane's intensity exactly reflect my reservations Re: Yasi! Check it out:

Thus it appears that Guayama may not have recorded the central pressure and 931 mb from the ship is retained as the central pressure in HURDAT at 18 UTC on the 13th and at landfall in Puerto Rico.

A 931 mb central pressure suggests winds of 129 kt from the south of 25N pressure-wind relationship.

The San Juan Weather Bureau office had recently replaced their old Robinson 4-cup anemometer with the more reliable 3-cup anemometer which has a minimal bias in high winds (Fergusson and Covert 1924). This anemometer measured peak 1 min winds of 139 kt at 1544 UTC at which time the anemometer lost one of its cups. Winds were estimated by the observer to have possibly been higher than this between 1830 and 1930 UTC (at the time of the closest approach of the hurricane). An RMW value of 25 nm is quite well established between the timing of the peak estimated winds at the San Juan Weather Bureau Office at 19 UTC and landfall of the hurricane’s center in southeast Puerto Rico just an hour earlier. There is no evidence that the 139 kt winds were caused by funneling between buildings or because of citing the anemometer on a tall building (J. Colon – personal communication).

The observed winds, central pressure, and size of the hurricane present a dilemma, in determining its intensity. The observed winds – which appear reliable – would suggest an intensity of at least 140 kt. This would, however, be much above the pressure-wind relationship. Typically, winds can be substantially above the wind suggested by the pressure-wind relationship if the cyclone has a fast translational velocity, small RMW, and/or high environmental pressure (Knaff and Zehr 2007). This hurricane apparently had none of these three, as the hurricane was only moving at about 12 kt in its transit across Puerto Rico, had a RMW of perhaps a large 25 nmi, and was embedded in environmental pressures of about 1010 mb.

We are unable here to successfully explain the discrepancy

, but will go with the observed winds to estimate an intensity of 140 kt at 18 UTC on the 13th and at landfall in Puerto Rico.

(One alternative possibility is that the 139 kt 1 min winds were associated with a transient mesoscale low and were not representative of the maximum winds in the eyewall of the hurricane.) This makes this hurricane – known as San Felipe in Puerto Rico – a Category 5 hurricane, which is consistent with the extreme wind caused damage across the island.

At the very least, this gives real validity to my arguments that Yasi was not a Cat 5-- because this is exactly the logic I've been using. They would never have called the San Felipe 'cane a Cat 5 if it weren't for that one surface ob-- which I'm frankly skeptical about-- but they clearly felt kind of obligated. Since we have no surface obs for Yasi even remotely approaching that velocity, it would seem hard to argue it was a Cat 5.

Anyhoo, good suggestion here-- because it really is an excellent analogue for Yasi.

[Scott747]

We really need to devise the mobile ability to obtain ground level obs instead of constantly guessing by the use of recon/sat,radar/limited personal obs and pressure relationship that at times doesn't add up.

Something in the line of the Stick-net probes that are fanned out up and down the path of any significant storm that gives us much better ground level data.

[bronxx]

Video of Dunk Island with some aerial footage. Video link is on the right of the article.

http://www.theaustra...e-1225999868555

Banana trees start snapping in the middle at 40-45 mph. So whoever planted that field must not have been expecting to see even a tropical storm in that area when he made said investment.

[Ed Lizard]

We really need to devise the mobile ability to obtain ground level obs instead of constantly guessing by the use of recon/sat,radar/limited personal obs and pressure relationship that at times doesn't add up.

Something in the line of the Stick-net probes that are fanned out up and down the path of any significant storm that gives us much better ground level data.

Australia has severe weather chase forums. They have enough tornadoes, you'd think one college in a reasonably affluent country would deploy its own version of the DOW for radar wind measurements.

And again, they have J model Hercules, it can't cost that much to equip a couple and train a crew. If our military could do it with 1940s airplanes, well...

[Normandy]

The San Felipe analog is a good one, and perhaps our understanding of hurricanes is not at a level where we can explain discrepancies like San Felipe and Yasi. The reading out of Townsville suggests a broad circulation, but it also suggests a very severe cyclone. Large cyclones like Ike and Katrina didn't produce hurricane force winds that far out so I can imagine that the southern eyewall could possibly have produced 140 kt winds (Carla is the only cane I can think of that at landfall has legit surface obs of hurricane force winds that far out). There is no evidence and it is all speculation. The microwave image, temperature gradient, and damage at ground zero I think is suggestive of a borderline 4/5....130-140 kts I'd say.

[HurricaneJosh]

The San Felipe analog is a good one, and perhaps our understanding of hurricanes is not at a level where we can explain discrepancies like San Felipe and Yasi. The reading out of Townsville suggests a broad circulation, but it also suggests a very severe cyclone. Large cyclones like Ike and Katrina didn't produce hurricane force winds that far out so I can imagine that the southern eyewall could possibly have produced 140 kt winds (Carla is the only cane I can think of that at landfall has legit surface obs of hurricane force winds that far out). There is no evidence and it is all speculation. The microwave image, temperature gradient, and damage at ground zero I think is suggestive of a borderline 4/5....130-140 kts I'd say.

I agree with most of your post except the bold part. Again, this logic is the opposite of the prevailing methodology with regard to intensity analysis. Generally, the greater the radial extent of hurricane winds, the lower the max winds for a given pressure. All the hurricane winds in Townsville tell us is that it was an extremely large, broad cyclone. The hurricane winds in Townsville actually make me feel it is less likely that the cyclone might have been Cat 5.

[k***]

wow i served it up to you on a silver platter!

kush, check out this very interesting read-- from the "additional notes" Re: the NHC's reanalysis of the San Felipe 1928 hurricane: http://www.aoml.noaa.gov/hrd/hurdat/metadata_1926-30.html#1928_additional

They set the PR landfall intensity at 931 mb/140 kt, but with great reservations. In the end, they based their whole verdict on what appeared to be a reliable surface ob from San Juan Weather Bureau Office-- 139 kt (1-min)!! Honestly, I am extremely skeptical Re: that reading-- I don't buy it. San Juan wasn't even near the landfall point!

Their reservations Re: the 1928 'cane's intensity exactly reflect my reservations Re: Yasi! Check it out:

Thus it appears that Guayama may not have recorded the central pressure and 931 mb from the ship is retained as the central pressure in HURDAT at 18 UTC on the 13th and at landfall in Puerto Rico.

A 931 mb central pressure suggests winds of 129 kt from the south of 25N pressure-wind relationship.

The San Juan Weather Bureau office had recently replaced their old Robinson 4-cup anemometer with the more reliable 3-cup anemometer which has a minimal bias in high winds (Fergusson and Covert 1924). This anemometer measured peak 1 min winds of 139 kt at 1544 UTC at which time the anemometer lost one of its cups. Winds were estimated by the observer to have possibly been higher than this between 1830 and 1930 UTC (at the time of the closest approach of the hurricane). An RMW value of 25 nm is quite well established between the timing of the peak estimated winds at the San Juan Weather Bureau Office at 19 UTC and landfall of the hurricane’s center in southeast Puerto Rico just an hour earlier. There is no evidence that the 139 kt winds were caused by funneling between buildings or because of citing the anemometer on a tall building (J. Colon – personal communication).

The observed winds, central pressure, and size of the hurricane present a dilemma, in determining its intensity. The observed winds – which appear reliable – would suggest an intensity of at least 140 kt. This would, however, be much above the pressure-wind relationship. Typically, winds can be substantially above the wind suggested by the pressure-wind relationship if the cyclone has a fast translational velocity, small RMW, and/or high environmental pressure (Knaff and Zehr 2007). This hurricane apparently had none of these three, as the hurricane was only moving at about 12 kt in its transit across Puerto Rico, had a RMW of perhaps a large 25 nmi, and was embedded in environmental pressures of about 1010 mb.

We are unable here to successfully explain the discrepancy

, but will go with the observed winds to estimate an intensity of 140 kt at 18 UTC on the 13th and at landfall in Puerto Rico.

(One alternative possibility is that the 139 kt 1 min winds were associated with a transient mesoscale low and were not representative of the maximum winds in the eyewall of the hurricane.) This makes this hurricane – known as San Felipe in Puerto Rico – a Category 5 hurricane, which is consistent with the extreme wind caused damage across the island.

At the very least, this gives real validity to my arguments that Yasi was not a Cat 5-- because this is exactly the logic I've been using. They would never have called the San Felipe 'cane a Cat 5 if it weren't for that one surface ob-- which I'm frankly skeptical about-- but they clearly felt kind of obligated. Since we have no surface obs for Yasi even remotely approaching that velocity, it would seem hard to argue it was a Cat 5.

Anyhoo, good suggestion here-- because it really is an excellent analogue for Yasi.

[am19psu]

I agree with most of your post except the bold part. Again, this logic is the opposite of the prevailing methodology with regard to intensity analysis. Generally, the greater the radial extent of hurricane winds, the lower the max winds for a given pressure. All the hurricane winds in Townsville tell us is that it was an extremely large, broad cyclone. The hurricane winds in Townsville actually make me feel it is less likely that the cyclone might have been Cat 5.

And it makes sense dynamically, too. If there is large wind field, the pressure gradient has to be more spread out, instead of being tightly packed in the inner core.

[k***]

Here's what I don't get about that san felipe observation--139kts at 1544 UTC and higher until 19:30? Even accounting for the slow forward motion that still seems a bit out of whack.

[HurricaneJosh]

Here's what I don't get about that san felipe observation--139kts at 1544 UTC and higher until 19:30? Even accounting for the slow forward motion that still seems a bit out of whack.

Yeah, that is weird. Also note San Juan's location in relation to the track. I find it almost unbelievable that they had 139 kt (1-min) from this system. I'm having trouble accepting it at face value.

[Normandy]

Does anyone know how high the winds got in Innisfaul sustained? I remember reading their was a gust at 120 kts. Perhaps what I meant to say was that because Yasi was a broad cyclone doesn't necessarily suggest it was a 5, but I don't think in this particular case you can say that because it was so broad it wasn't a 5 (because of the additional damage pics supporting a borderline 4/5). One thing I was wondering about was the symmetry of Yasi's windfield. It seemed very assymetric with most of the heavy winds being south of the track and very far out. How far north did the hurricane force winds extend?

[ninox33]

Nice discussion all

We can't afford F18s we just buy them because we are told too

Randomly answering some past questions

Yes Bedarra was hit hard, damage to resort and one private house destroyed

Video link below to Hull Heads, focal point of crossing and showing evidence of large storm surge

http://media.smh.com.au/national/national-news/yasi-damage-setting-in-for-residents-2169549.html?&exc_from=strap

I agree with one comment re size of yasi and low pressure gradient, so I'd agree with cat 4 Aussie scale

Yasi was by our standards an Atlantic size system

Remember the damage to Dunk resort would have mostly occurred in the trailing eye-wall, images from the south end of the island would reveal what the leading edge did, I'd imagine the artist's colony is gone

The rest of what you guy's are saying is over my head lol

[am19psu]

I agree with one comment re size of yasi and low pressure gradient, so I'd agree with cat 4 Aussie scale

I'm willing to be wrong here, but I think all of us are in agreement that this was a Cat 5 Aussie system. We're just discussing whether it would make Cat 5 on the U.S. Saffir-Simpson scale.

[k***]

I'm willing to be wrong here, but I think all of us are in agreement that this was a Cat 5 Aussie system. We're just discussing whether it would make Cat 5 on the U.S. Saffir-Simpson scale.

Indeed.

[ninox33]

http://goaustralia.about.com/od/practicalinformation/f/cyclones.htm

I have seen quotes of wind gusts above 280kph (e.g. 290kph)

Where were they?

Still thinking top end of Cat 4 Oz scale

[ninox33]

Ex-Yasi still has good organisation

http://www.bom.gov.au/products/national_radar_sat.loop.shtml

Expected to head NW, could be re-named in 5-6 days

http://www.bom.gov.au/australia/charts/4day_col.shtml

Good high to its south to assist this transition

[HurricaneJosh]

Does anyone know how high the winds got in Innisfaul sustained? I remember reading their was a gust at 120 kts. Perhaps what I meant to say was that because Yasi was a broad cyclone doesn't necessarily suggest it was a 5, but I don't think in this particular case you can say that because it was so broad it wasn't a 5 (because of the additional damage pics supporting a borderline 4/5). One thing I was wondering about was the symmetry of Yasi's windfield. It seemed very assymetric with most of the heavy winds being south of the track and very far out. How far north did the hurricane force winds extend?

I don't know what the highest sustained wind at Innisfail was-- I'd like to know, too. Judging from the reports and the damage, I would assume they had a hurricane wind at least. And I'm pretty sure Cairns didn't. The windfield was extremely asymmetric, I think-- which makes sense, given the fast forward motion. And it aligns well with the BoM forecasts, as their maps always showed it coming ashore with a lopsided windfield.

Nice discussion all

We can't afford F18s we just buy them because we are told too

Randomly answering some past questions

Yes Bedarra was hit hard, damage to resort and one private house destroyed

Video link below to Hull Heads, focal point of crossing and showing evidence of large storm surge

http://media.smh.com.au/national/national-news/yasi-damage-setting-in-for-residents-2169549.html?&exc_from=strap

I agree with one comment re size of yasi and low pressure gradient, so I'd agree with cat 4 Aussie scale

Yasi was by our standards an Atlantic size system

Remember the damage to Dunk resort would have mostly occurred in the trailing eye-wall, images from the south end of the island would reveal what the leading edge did, I'd imagine the artist's colony is gone

The rest of what you guy's are saying is over my head lol

Hey, this is a dumb question, but how do you know the Dunk resort damage was done by the cyclone's backside?

Interesting link Re: Hull Heads. One comment caught my attention: the elderly dude, who rode out the cyclone there, said "the wind was alright", but it was the water that freaked him out. That surprised me a bit, because Hull Heads was probably very near the wind max, and I don't think anyone in the wind max of a 130-kt cyclone wouldn't be a little freaked by those winds. So the comment makes me wonder a bit. (Just when I keep feeling ready to close the book on this discussion of Yasi's intensity, some little detail throws me off a little. Grrrr.)

P.S. As am19psu said, above-- the prevailing opinion on this board is that Yasi was an Aussie Cat 5 and a strong American Cat 4. Out of curiosity, why don't you think it was an Aussie Cat 5? It seemed to have had all the ingredients...

I'm willing to be wrong here, but I think all of us are in agreement that this was a Cat 5 Aussie system. We're just discussing whether it would make Cat 5 on the U.S. Saffir-Simpson scale.

Yep.

[HurricaneJosh]

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.

Hi, Mardi!

I missed this post yesterday-- so sorry for not responding earlier!

First off, I'm glad to hear you got through the cyclone OK. I was thinking about you as the cyclone came ashore, and looking at the track and the maps, my impression was that the core of the cyclone passed to your S, but that you most certainly got some heavy conditions. How windy did it get? Any damage? Anyhoo, I'm glad you're OK.

Also, please let us know what you see down in Cardwell-- I'm curious.

[ninox33]

i lived on Dunk for 6 months so very familiar with the island

Long ridge and mountain runs the length of the eastern side of the island with more ridges running to the western side

Watching it cross I felt leading winds would have done some damage but the resort is tucked in a bay protected from the east, south east and some what from the south, but when the trailing edge crossed the resort would have been fully exposed to all Yasi could deliver

Saw a pic of mission beach today and the palms had all their fronds (only1 pic so it could be random and isolated) so Dunk did appear to cop more

I might not be as technically with it as many of the esteemed posters here but

I saw the after affects and a have a pic of pre and post Ingrid crossing Black Point and defoliation was similar if not worse (2005?), will find later and post she was Cat 4?

I liked the comment before re the size of Yasi and therefore the weaker?uncompressed?flatter? pressure gradient made good sense of what happened

Yasi was an unusual cyclone for us but I still go with high-end Cat 4, post BOM analysis may prove me wrong

A lot of on ground but not literate people are saying the noise was immense but on ground wind did not match? is this possible? Can the destructive winds be more intense 20-100m higher?

So you guys can make an analysis based on good technical data and media images, the BOM will do it on that and ground truthing, I can only go with my gut feelings and having watched most cyclones develop, cross and miss Oz since the 80's, but to me it was huge and the media hype was extensive the govt and BOM reacted well if not too well after the stuff ups of the Brisbane floods

As I said earlier and posted a link, I have heard mention of a 290kph gust, I would like to see more evidence that +280kph winds were recorded

Anyway its just my opinion and I know I could be/probably are wrong, but I still hang my hat on that call with no technical evidence to back it up, I just don't see it adding up

Post script: I do believe Tracy was severe, excessively and building codes don't come into play like many people make out, steel isn't coded as Paul (NAC) was saying, here's a picture of Darwin power poles after Tracy

Sorry if my ramblings irk others PM me and I will happily lurk and learn more

[HurricaneJosh]

Sorry if my ramblings irk others PM me and I will happily lurk and learn more

I'm running out now and will respond in more detail later, but wanted to say that your insights here are welcomed-- so please don't be silly! There's no reason for you to stay quiet and lurk. Not everyone in this group has the same level of knowledge, and either way, you certainly know more about Aussie cyclones than most here-- so therefore your inputs are automatically relevant!

Catch ya later.

[ninox33]

Cyclone Ingrid March - 2006

Eucalyptus tree turned into spear on Melville Island

Pre and post Ingrid crossing Black Point Cobourg Pen.

Barometer print out ( I assume this was on Black Point with eye crossing)

I haven't looked at your Ingrid and Monica threads but I will find them but I thought these would be interesting even if unrelevant

[k***]

Cyclone Ingrid March - 2006

<snip>

I haven't looked at your Ingrid and Monica threads but I will find them but I thought these would be interesting even if unrelevant

Impressive photos and barogram...I love the construction you guys have down under--it's like after Tracy everyone went nuts with the building codes and you get scenes like Dunk island and the one you posted above where all the trees get denuded but building roofs stay attached.

Don't bother looking for Monica and Ingrid threads--this board has only existed since November 2010. Much of our history before that has been lost into the internet void, and even if it weren't this group of folks wasn't as gung-ho about following Southern Hemisphere stuff until after those storms.

[aslkahuna]

To ninox, most certainly yes the winds could be significantly stronger 100 m off the ground.. In fact, here in the US the NHC makes a point of advising people in cities when a strom is headed for one that the winds in the upper levels of high rises could be as much as one full category stronger than on on the ground. The hurricane's (and TC's) strongest winds are found some some distance above ground level. This is where the role of convection in the eyewall comes into play for the downdrafts in the convection will surface the stronger winds as gusts. This convection is stronger in storms that are intensifying rather than steady state or weakening. Mesoscale structures within the eyewall such as mesovortices can also surface these stronger winds. Such structures are usually found in intensifying storms as well and can result in localized winds far more intense than those supported by the pressure gradient.

Steve

[battlebrick]

I haven't looked at your Ingrid and Monica threads but I will find them but I thought these would be interesting even if unrelevant

There's a Monica thread on s2k.

http://www.storm2k.org/phpbb2/viewtopic.php?f=55&t=83439

[HurricaneJosh]

So I guess we can close the book on the Yasi landfall intensity discussion. It seems the general consensus here is a strong USA Cat 4-- which conforms well with a blend of the BoM and JTWC estimates. We can leave it at that.

Peace for our time.

[ninox33]

Yasi showed signs of further intensification and at 4am on 2nd February and was upgraded to a marginal Category 5 system. Yasi maintained this intensity and its west-southwest movement, making landfall on the southern tropical coast near Mission Beach between midnight and 1am early on Thursday 3rd February. Being such a strong and large system, Yasi maintained a strong core with damaging winds and heavy rain, tracking westwards across northern Queensland and finally weakened to a tropical low near Mount Isa around 10pm on 3rd February.

Interim BOM summary with relevant figures, images and preliminary summary

My link

[HurricaneJosh]

Wow-- that's cool that the BoM has already issued a preliminary report! Such immediate gratification!

[HurricaneJosh]

Be aware its a prelim... you will find lowest pressure was 922 and that it was cat 5 100km inland. Also certain recording elements will be up for serious review.

Yeah, we note that it's preliminary.

Where did you get the 922 mb? Was that measured by a reliable station?

[HurricaneJosh]

Not published yet but eminently reliable.

Can you name your source-- and the location where it was measured? It's so much lower than the Clump Point and Tully readings, of course we're going to have questions about its origins.