Discussion of Intense Tropical Cyclones

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Re: Discussion of Intense Tropical Cyclones

#521 Postby euro6208 » Thu Oct 29, 2020 10:30 am

Weather Dude wrote:
euro6208 wrote:
aspen wrote:165 kt is a very good estimate for Halong. It was extremely intense, but it was just a little below a perfect T#8.0/170 kt TC. Hagibis, on the other hand, was likely in the 160-175 kt range.

Speaking of WPac systems, it’s very likely we’ll be talking about Goni and/or Atsani here soon. Goni is going through a phase of ERI and is developing a rapidly warming pinhole eye. Models are very aggressive with Atsani, far more than Goni. It seems like Goni could be similar to Hagibis and Atsani could be similar to Halong, in terms of structure.


Can you say the same for Dorian. Estimates peaked at below 140 knots. Yet recon....

Not all storms are stronger than estimates. Look at Zeta, it had Cat 4 estimates there for a bit and it clearly wasn't a Cat 4. Recon goes both ways


Cat 5's are a different story.

A majority are stronger than estimates and that includes TS to Cat 4.
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Re: Discussion of Intense Tropical Cyclones

#522 Postby Weather Dude » Thu Oct 29, 2020 10:44 am

euro6208 wrote:
Weather Dude wrote:
euro6208 wrote:
Can you say the same for Dorian. Estimates peaked at below 140 knots. Yet recon....

Not all storms are stronger than estimates. Look at Zeta, it had Cat 4 estimates there for a bit and it clearly wasn't a Cat 4. Recon goes both ways


Cat 5's are a different story.

A majority are stronger than estimates and that includes TS to Cat 4.

Sure they can be. And I agree we need recon out there in the WPAC badly. But you can't compare every storm to Dorian. Most Cat 5's of that intensity have much colder convection than Dorian had. Dorian was the exception not the norm
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Re: Discussion of Intense Tropical Cyclones

#523 Postby euro6208 » Thu Oct 29, 2020 10:49 am

Weather Dude wrote:
euro6208 wrote:
Weather Dude wrote:Not all storms are stronger than estimates. Look at Zeta, it had Cat 4 estimates there for a bit and it clearly wasn't a Cat 4. Recon goes both ways


Cat 5's are a different story.

A majority are stronger than estimates and that includes TS to Cat 4.

Sure they can be. And I agree we need recon out there in the WPAC badly. But you can't compare every storm to Dorian. Most Cat 5's of that intensity have much colder convection than Dorian had. Dorian was the exception not the norm


Vice Versa. If Dorian didn't had recon, it would have peaked at 135-140 knots.
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Re: Discussion of Intense Tropical Cyclones

#524 Postby euro6208 » Thu Oct 29, 2020 10:56 am

Image
Image

How can this be?
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Re: Discussion of Intense Tropical Cyclones

#525 Postby Weather Dude » Thu Oct 29, 2020 10:57 am

euro6208 wrote:
Weather Dude wrote:
euro6208 wrote:
Cat 5's are a different story.

A majority are stronger than estimates and that includes TS to Cat 4.

Sure they can be. And I agree we need recon out there in the WPAC badly. But you can't compare every storm to Dorian. Most Cat 5's of that intensity have much colder convection than Dorian had. Dorian was the exception not the norm


Vice Versa. If Dorian didn't had recon, it would have peaked at 135-140 knots.

Yeah definitely. I'm saying that most storms that have the estimates that Dorian had without recon are not 160kt Cat 5's.
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Re: Discussion of Intense Tropical Cyclones

#526 Postby euro6208 » Fri Oct 30, 2020 4:13 am

Cat 5 Goni


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Re: Discussion of Intense Tropical Cyclones

#527 Postby aspen » Fri Oct 30, 2020 5:36 am


Goni’s phase of RI has been nothing short of monumental. In just 24 hours, winds have increased by 95 mph — it has gone from a 70 kt/80 mph Cat 1 to a 150 kt/175 mph Cat 5. This far surpasses the RI phases of Delta and Amphan, and is easily one of the most extreme phases of ERI seen in the last decade or so.
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Re: Discussion of Intense Tropical Cyclones

#528 Postby aspen » Fri Oct 30, 2020 10:25 am

WAcyclone wrote:I am absolutely fascinated by this comparison of GOES-16 30-second imagery from Michael and Dorian:


https://twitter.com/weatherdak/status/1168998046937600001
Although both loops have exactly the same temporal and spatial resolution, you can clearly see that the eyewall of Dorian is spinning much faster than Michael's. So I wonder if it may be possible to roughly estimate the wind speed of storms with well-developed eyes based on the speed of rotation visible in these high-frequency images? Does anyone know if there has been any research looking into this?

I tried to estimate the visible eyewall rotation speed for both storms myself by tracking some discernible cloud features in the lower part of the inner eyewall for 5 min (10 frames). Given that the image resolution is approx. 500 metres per pixel, it is then possible to estimate how far these features have travelled around the eye during this time. The results were quite interesting, albeit probably not very accurate. The features I tracked for Dorian moved quite constantly at a speed of 250-270 km/h (135-146 kt) while those of Michael moved at 170-200 km/h (92-108 kt). Based on these calculations, the visible eyewall of Dorian rotated approx. 30-50 % faster than the one of Michael which is in line with what I would have guessed by just looking at Dakota Smith's comparison loop.

This could be used to try and determine Goni’s peak intensity. There were visible shots leading up to its 150 kt upgrade.
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Re: Discussion of Intense Tropical Cyclones

#529 Postby Shell Mound » Fri Oct 30, 2020 12:36 pm

aspen wrote:

Goni’s phase of RI has been nothing short of monumental. In just 24 hours, winds have increased by 95 mph — it has gone from a 70 kt/80 mph Cat 1 to a 150 kt/175 mph Cat 5. This far surpasses the RI phases of Delta and Amphan, and is easily one of the most extreme phases of ERI seen in the last decade or so.

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Source

Goni’s peak intensity was probably on par with Haiyan’s, if not a bit higher, based on satellite data, forward speed, RMW, and background pressure, along with ERI.
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Re: Discussion of Intense Tropical Cyclones

#530 Postby WAcyclone » Fri Oct 30, 2020 4:49 pm

aspen wrote:
WAcyclone wrote:I am absolutely fascinated by this comparison of GOES-16 30-second imagery from Michael and Dorian:


https://twitter.com/weatherdak/status/1168998046937600001
Although both loops have exactly the same temporal and spatial resolution, you can clearly see that the eyewall of Dorian is spinning much faster than Michael's. So I wonder if it may be possible to roughly estimate the wind speed of storms with well-developed eyes based on the speed of rotation visible in these high-frequency images? Does anyone know if there has been any research looking into this?

I tried to estimate the visible eyewall rotation speed for both storms myself by tracking some discernible cloud features in the lower part of the inner eyewall for 5 min (10 frames). Given that the image resolution is approx. 500 metres per pixel, it is then possible to estimate how far these features have travelled around the eye during this time. The results were quite interesting, albeit probably not very accurate. The features I tracked for Dorian moved quite constantly at a speed of 250-270 km/h (135-146 kt) while those of Michael moved at 170-200 km/h (92-108 kt). Based on these calculations, the visible eyewall of Dorian rotated approx. 30-50 % faster than the one of Michael which is in line with what I would have guessed by just looking at Dakota Smith's comparison loop.

This could be used to try and determine Goni’s peak intensity. There were visible shots leading up to its 150 kt upgrade.


I think this method may be used to compare relative intensities among storms with similar-sized eyes, not for actual peak intensity estimates. Himawari-8 also only produces 2.5-minute imagery, not the 30-second one I used for this analysis. The pinhole-sized eye of Goni further complicates it. However, there should be a new SMAP pass of Goni coming up soon which will certainly be one of the most interesting ones so far ;)
Last edited by WAcyclone on Fri Oct 30, 2020 5:57 pm, edited 1 time in total.
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Re: Discussion of Intense Tropical Cyclones

#531 Postby aspen » Fri Oct 30, 2020 5:21 pm

WAcyclone wrote:
aspen wrote:
WAcyclone wrote:I am absolutely fascinated by this comparison of GOES-16 30-second imagery from Michael and Dorian:


https://twitter.com/weatherdak/status/1168998046937600001
Although both loops have exactly the same temporal and spatial resolution, you can clearly see that the eyewall of Dorian is spinning much faster than Michael's. So I wonder if it may be possible to roughly estimate the wind speed of storms with well-developed eyes based on the speed of rotation visible in these high-frequency images? Does anyone know if there has been any research looking into this?

I tried to estimate the visible eyewall rotation speed for both storms myself by tracking some discernible cloud features in the lower part of the inner eyewall for 5 min (10 frames). Given that the image resolution is approx. 500 metres per pixel, it is then possible to estimate how far these features have travelled around the eye during this time. The results were quite interesting, albeit probably not very accurate. The features I tracked for Dorian moved quite constantly at a speed of 250-270 km/h (135-146 kt) while those of Michael moved at 170-200 km/h (92-108 kt). Based on these calculations, the visible eyewall of Dorian rotated approx. 30-50 % faster than the one of Michael which is in line with what I would have guessed by just looking at Dakota Smith's comparison loop.

This could be used to try and determine Goni’s peak intensity. There were visible shots leading up to its 150 kt upgrade.


I think this method may be used to compare relative intensities among storms with similar-sized eyes, not for actual peak intensity estimates. Himawari-8 also only produces 2.5-minute imagery, not the 30-second one I used for this analysis. The pinhole-sized eye of Goni further complicates it. However, there should be a new SMAP pass of Goni coming up in a few minutes which will certainly be one of the most interesting ones so far ;)

I hope SMAP gets a good pass like it did with Bualoi. Using it, we could work backwards to try an estimate Goni’s true peak winds, and perhaps reverse the KCZ formula to estimate pressure.
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Re: Discussion of Intense Tropical Cyclones

#532 Postby Ubuntwo » Fri Oct 30, 2020 5:31 pm

aspen wrote:
WAcyclone wrote:
aspen wrote:This could be used to try and determine Goni’s peak intensity. There were visible shots leading up to its 150 kt upgrade.


I think this method may be used to compare relative intensities among storms with similar-sized eyes, not for actual peak intensity estimates. Himawari-8 also only produces 2.5-minute imagery, not the 30-second one I used for this analysis. The pinhole-sized eye of Goni further complicates it. However, there should be a new SMAP pass of Goni coming up in a few minutes which will certainly be one of the most interesting ones so far ;)

I hope SMAP gets a good pass like it did with Bualoi. Using it, we could work backwards to try an estimate Goni’s true peak winds, and perhaps reverse the KCZ formula to estimate pressure.

Older Sentinel-1 overpass:
 https://twitter.com/CYMS_S1/status/1322183687560142854


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Re: Discussion of Intense Tropical Cyclones

#534 Postby aspen » Fri Oct 30, 2020 6:13 pm

Goni might be >165 kt now. Despite an outer eyewall forming, the inner eyewall has been quite vigorous, and convection has rapidly deepened to a nearly complete CDG ring.
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Re: Discussion of Intense Tropical Cyclones

#535 Postby aspen » Fri Oct 30, 2020 6:44 pm

CDO is comparable to the deepness of Halong, which peaked at T#7.8/7.9. However, this has a far more compact eye, and SAR recorded instantaneous winds of up to 190 kt. I think there's a reasonable argument for Goni being 170 kt (195 mph).
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Re: Discussion of Intense Tropical Cyclones

#536 Postby aspen » Sat Oct 31, 2020 2:03 pm

Officially 170 kt and 884 mbar from the JTWC...just, holy ****.
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Re: Discussion of Intense Tropical Cyclones

#537 Postby euro6208 » Sat Oct 31, 2020 2:11 pm

Shortly will be the strongest landfalling tropical cyclone in world history. Ouch.
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Re: Discussion of Intense Tropical Cyclones

#538 Postby TorSkk » Sat Oct 31, 2020 7:05 pm

I think that Goni will once again bring up the discussion about CDG rules in manual Dvorak estimates. SAB obtained T8.0 the "experimental" way, with 7.0 for an eye embedded within CDG and 1.0 as the adjustment for WMG. JTWC went the "traditional" way and got a CF of 7.5 then added 0.5 for banding. It's also with noting that the MET has to be higher than CF to add a banding feature. @1900hurricane explored this further here
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Re: Discussion of Intense Tropical Cyclones

#539 Postby CrazyC83 » Sat Oct 31, 2020 8:58 pm

I estimate Goni was 175 kt at its peak, perhaps 180 kt. Very close to Haiyan and Patricia.
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Re: Discussion of Intense Tropical Cyclones

#540 Postby NotoSans » Sat Oct 31, 2020 10:45 pm

My personal thought is that Goni's first peak is stronger than the second peak. It doesn't mean that the second peak is not strong, just that the first peak is even stronger.

Eye temperature during the second peak oscillated between OW and WMG range, which is not a typical sign observed in "top typhoons" (See Nepartak, Megi and Meranti). In contrast, eye temperature during the first peak is persistently WMG, even reaching 20C+ range.

Of course, objective aids in the second peak indicate a stronger intensity, but the core and circulation during the first peak is very small that I doubt any objective aid can reasonably resolve the storm.
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