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Cyclone Yasi


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Hey, Mardi--

Well, you're very welcome! I'm glad you've found the discussions helpful. :)

I often think about what you just mentioned-- how weird it must have been years ago to wake up to a nice day, and then experience a really severe cyclone without expecting it. It must have been bizarre and disorienting. Many of the biggest hurricane disasters in the USA happened that way early last century-- the storms were complete surprises.

Anyhoo, you're in for a bumpy ride, so get ready. Looks like you're going to be right in the core of this one. Please post observations as long as you can-- we'd like to know what you're experiencing as the center nears your location.

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Huh? That's just weird. I mean, it looks good to me, but I'm not sure it looks that good. It's not terribly symmetric...

Thoughts?

Symmetry does not matter for the Dvorak technique once an eye is present. It's only the difference between the coldest convection and the warmest temperatures in the eye. As kush said, it doesn't have that classical Cat 5 clear eye, so it's probably reading a bit high, but 130ish is close to right at this time. SATCON hasn't updated since 15z, but that has the lowest error rate compared to aircraft obs of any remote platform (including manual analysis), so that will be the best judge, once we get an update.

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Symmetry does not matter for the Dvorak technique once an eye is present. It's only the difference between the coldest convection and the warmest temperatures in the eye. As kush said, it doesn't have that classical Cat 5 clear eye, so it's probably reading a bit high, but 130ish is close to right at this time. SATCON hasn't updated since 15z, but that has the lowest error rate compared to aircraft obs of any remote platform (including manual analysis), so that will be the best judge, once we get an update.

OK, cool-- thanks for explaining that. I didn't know symmetry didn't count for Dvorak. (I should sit down and read how it works more closely-- I've only skimmed it in the past.)

I was just surprised by that pressure calculation-- not so much the wind estimate.

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I was just surprised by that pressure calculation-- not so much the wind estimate.

Oh, sorry, I should have explained that too. ADT produces a wind speed estimate from the Dvorak technique and then uses a P-W relationship to back out the pressure. UW apparently doesn't have a P-W relationship for the Southern Hemisphere, so they use the NW Pacific P-W relationship, which is obviously erroneous.

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OK, cool-- thanks for explaining that. I didn't know symmetry didn't count for Dvorak. (I should sit down and read how it works more closely-- I've only skimmed it in the past.)

I was just surprised by that pressure calculation-- not so much the wind estimate.

Pressure wise, I've always thought ADT is too low in this basin...They use the WPAC relationship but I don't think it lines up as well in the Coral sea.

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Oh, sorry, I should have explained that too. ADT produces a wind speed estimate from the Dvorak technique and then uses a P-W relationship to back out the pressure. UW apparently doesn't have a P-W relationship for the Southern Hemisphere, so they use the NW Pacific P-W relationship, which is obviously erroneous.

^

this

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Yeah, I am going to put my foot down and declare no to a 5...that eye simply isn't there.

Nice 4, though :)

Agreed. It's not a Cat 5 on our scale. It's a good 4. If I was shown these images cold, I would guess 120 kt.

Oh, sorry, I should have explained that too. ADT produces a wind speed estimate from the Dvorak technique and then uses a P-W relationship to back out the pressure. UW apparently doesn't have a P-W relationship for the Southern Hemisphere, so they use the NW Pacific P-W relationship, which is obviously erroneous.

Ah, OK-- thanks.

Pressure wise, I've always thought ADT is too low in this basin...They use the WPAC relationship but I don't think it lines up as well in the Coral sea.

Bingo-- Adam agrees.

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Hey, Mardi--

Well, you're very welcome! I'm glad you've found the discussions helpful. :)

I often think about what you just mentioned-- how weird it must have been years ago to wake up to a nice day, and then experience a really severe cyclone without expecting it. It must have been bizarre and disorienting. Many of the biggest hurricane disasters in the USA happened that way early last century-- the storms were complete surprises.

Anyhoo, you're in for a bumpy ride, so get ready. Looks like you're going to be right in the core of this one. Please post observations as long as you can-- we'd like to know what you're experiencing as the center nears your location.

This is why I love reading about old storms. Whether the accounts are scientifically accurate is another matter, sometimes the humanism of the situation overtakes objectivity and you have to be in awe with what people went through before the satellite era.

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This is why I love reading about old storms. Whether the accounts are scientifically accurate is another matter, sometimes the humanism of the situation overtakes objectivity and you have to be in awe with what people went through before the satellite era.

Yeah, like people in Westhampton, NY, on 21 September 1938. That must have been one big bag of WTF? :D

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One last thing about using the WPAC relationship--that's why ADT got down to 869 for Monica.

Yeah, I don't think the ADT is the best platform we have to objectively measure intensity, though it does fare better in eye scenarios. It's cool to look at, but I would never argue intensity with ADT alone. Now, if SATCON comes in at 135, then I think you have to give it a bit more credence.

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Yeah, like people in Westhampton, NY, on 21 September 1938. That must have been one big bag of WTF? :D

I so want to lurk in the New York and New England subforums when a major is headed North inside 70ºW past Hatteras...

But, in the meantime,

r711310_5563067.jpg

Severe Tropical Cyclone Yasi was upgraded to category five off north Queensland this morning as the weather bureau warned it was likely to be "more life-threatening" than any storm seen in Australia in living memory.

The weather bureau says Cyclone Yasi is a large and very powerful tropical cyclone and poses an "extremely serious threat" to life and property within the warning area, especially between Port Douglas and Townsville.

"This impact is likely to be more life-threatening than any experienced during recent generations," the Bureau of Meteorology (BOM) said this morning.

Tens of thousands of people are fleeing their homes ahead of the monster storm, which is expected to hit the coast between Cairns and Innisfail some time tonight.

This morning it was estimated to be 650 kilometres east north-east of Cairns and 650 kilometres north-east of Townsville, moving west south-west at 30 kilometres per hour.

The bureau says the low category five cyclone will continue to move in a west-southwesterly direction during today, but could become a high category five before making landfall.

Senior bureau forecaster Gordon Banks says it could take at least 24 hours for Cyclone Yasi to weaken after it makes landfall.

"There's still potential for it to become stronger ... as a strong category five we could see wind gusts in excess of 320 kilometres an hour. Which is just horrific."

http://www.abc.net.au/news/stories/2011/02/02/3127394.htm

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Yeah, I don't think the ADT is the best platform we have to objectively measure intensity, though it does fare better in eye scenarios. It's cool to look at, but I would never argue intensity with ADT alone. Now, if SATCON comes in at 135, then I think you have to give it a bit more credence.

Yeah, SATCON is so much better because it at least uses a blend of IR and microwave. This storm has been a good example of the way that IR and microwave presentations can sometimes be disjointed/misleading.

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Yeah, like people in Westhampton, NY, on 21 September 1938. That must have been one big bag of WTF? :D

Yeah, one of these days someone should collect accounts of great hurricanes/typhoons/cyclones in every basin and put them in a book. 1938 would definitely be near the top for our area. There's a few others I would include also-- how about the 1924 cat 5 that hit Cuba or the 1935 Labor Day Hurricane?

http://en.wikipedia...._Cuba_hurricane

The 1924 Cuba hurricane is the earliest officially classified Category 5 Atlantic hurricane on the Saffir–Simpson scale. It formed on October 14 in the western Caribbean Sea, slowly organizing as it tracked northwestward. By October 16, it attained hurricane status to the east of the Yucatán Peninsula, and subsequently executed a small counterclockwise loop. On October 18, the hurricane began undergoing rapid deepening, and the next day it reach an estimated peak intensity of 165 miles per hour (270 kilometres per hour). Shortly thereafter, it struck extreme western Cuba at peak intensity, becoming the strongest hurricane on record to hit the country.

http://en.wikipedia....ntic_hurricanes

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One thing is certain... the immense size of this storm combined with the funneling effects of the coastline near Cardwell and Townsville is going to produce some crazy surges.

The amount of rain this system drops is going to be crazy, too. Those poor people in Queensland. Hopefully the rest of the cyclone season/summer goes off without much rain headed their way.

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One thing is certain... the immense size of this storm combined with the funneling effects of the coastline near Cardwell and Townsville is going to produce some crazy surges.

The amount of rain this system drops is going to be crazy, too. Those poor people in Queensland. Hopefully the rest of the cyclone season/summer goes off without much rain headed their way.

The cyclone is moving very fast and will be accelerating even more-- so the rainfall might not be too bad for a system of this size.

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