Discussion of Intense Tropical Cyclones

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Re: Discussion of Intense Tropical Cyclones

#581 Postby supercane4867 » Mon Nov 16, 2020 5:26 pm

Recon observation in recent years confirm my suspicion that Isabel at her peak was the most underrated Category 5 Atlantic hurricane(probably by far).
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Re: Discussion of Intense Tropical Cyclones

#582 Postby aspen » Mon Nov 16, 2020 5:57 pm

supercane4867 wrote:Recon observation in recent years confirm my suspicion that Isabel at her peak was the most underrated Category 5 Atlantic hurricane(probably by far).

Why? Do you think it was much stronger than what Dvorak/IR appearance might suggest, like Irma and Dorian?
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Re: Discussion of Intense Tropical Cyclones

#583 Postby Ryxn » Mon Nov 16, 2020 6:11 pm

Did you know the 5-year CAT 5 hurricane streak from 2016-20 featured the southernmost (Matthew), northernmost (Michael) AND easternmost CAT 5s on record! Talk about a lust for breaking records...
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Re: Discussion of Intense Tropical Cyclones

#584 Postby CyclonicFury » Mon Nov 16, 2020 6:15 pm

Ryxn wrote:Did you know the 5-year CAT 5 hurricane streak from 2016-20 featured the southernmost (Matthew), northernmost (Michael) AND easternmost CAT 5s on record! Talk about a lust for breaking records...

I suspect Matthew may be a downgrade candidate in the future if SFMR is determined to be unreliable in very intense TCs. At the time of Matthew's peak (assessed by NHC as 145 kt at 00z October 1), a blend of flight-level and SFMR data only supported an intensity of 130-135 kt. If Matthew were to be downgraded to Category 4 in the future, I believe Iota would become the southernmost Atlantic Category 5 on record.
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Re: Discussion of Intense Tropical Cyclones

#585 Postby supercane4867 » Mon Nov 16, 2020 6:26 pm

aspen wrote:
supercane4867 wrote:Recon observation in recent years confirm my suspicion that Isabel at her peak was the most underrated Category 5 Atlantic hurricane(probably by far).

Why? Do you think it was much stronger than what Dvorak/IR appearance might suggest, like Irma and Dorian?

The first recon mission into Isabel arrived only after the hurricane had completed a full-ERC and recon still recorded peak 700mb flight level winds of 158kt(!). FWIW, that's higher than Dean's readings at landfall in Yucatan(154kt). Given that the IR presentation of Isabel at peak intensity is actually better than Irma and Dorian(all 3 systems peaked during daylight time), I'd personally put Isabel at 160kt minimum tbh.
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Re: Discussion of Intense Tropical Cyclones

#586 Postby 1900hurricane » Mon Nov 16, 2020 11:25 pm

Wow these last three weeks have been pretty crazy. Definitely have some thoughts to share when I get a chance.
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Re: Discussion of Intense Tropical Cyclones

#587 Postby CrazyC83 » Tue Nov 17, 2020 1:12 am

supercane4867 wrote:
aspen wrote:
supercane4867 wrote:Recon observation in recent years confirm my suspicion that Isabel at her peak was the most underrated Category 5 Atlantic hurricane(probably by far).

Why? Do you think it was much stronger than what Dvorak/IR appearance might suggest, like Irma and Dorian?

The first recon mission into Isabel arrived only after the hurricane had completed a full-ERC and recon still recorded peak 700mb flight level winds of 158kt(!). FWIW, that's higher than Dean's readings at landfall in Yucatan(154kt). Given that the IR presentation of Isabel at peak intensity is actually better than Irma and Dorian(all 3 systems peaked during daylight time), I'd personally put Isabel at 160kt minimum tbh.


I know Isabel was borderline T7.5 in the pre-Recon period, which on its own would suggest 150-155 kt. When Recon got there, it was just under T7.0 and Recon supported 145 kt. I'd at least go 155 kt for Isabel's peak (pre-Recon), with 160 kt a reasonable estimate as well.
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Re: Discussion of Intense Tropical Cyclones

#588 Postby Kingarabian » Tue Nov 17, 2020 4:08 am

1900hurricane wrote:Wow these last three weeks have been pretty crazy. Definitely have some thoughts to share when I get a chance.

Can't wait to get your take!
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Re: Discussion of Intense Tropical Cyclones

#589 Postby 1900hurricane » Sun Nov 22, 2020 5:41 pm

Over the past month prior to the time of this post, three noteworthy intense TCs have occurred: Super Typhoon Goni in the Western Pacific, Hurricane Eta in the Northern Atlantic, and Hurricane Iota also in the NAtl. Between these three higher end TCs, I think the only blanket statement that can be applied is that we still have a long way to go in fully understanding the characteristics of intense TCs, especially remotely.

Let's start with Hurricane Eta. Unfortunately, the missions planned for Eta were plagued with all kinds of maintenance issues. This made recon data during the intensification period sparse, and it was difficult to tell how quickly the system was actually intensifying. Once a plane was actually able to make it to the system, the intrigue was sky high, but actual data from the plane ended up falling well short of some of the more traditional IR estimation techniques, especially that of ADT. Even with constraints in place, the ADT estimates were generally 20ish kt too high near peak intensity (at least as operationally assessed). Remove those constraints, and the estimate becomes even more hyperbolic. So what was the deal with Eta, a TC with a modestly symmetric CMG and even at times CDG CDO and an eye that would flirt with and occasionally cross the WMG threshold?

Image

I think largely in Eta's case, some of the environmental factors prevented it from fully hitting its stride. In particular, it appeared that there was some easterly shear impinging on the system below anvil level and possibly extending down into the mid-levels. As it appeared to be almost entirely below the very high and cold CDO anvil, the shear was somewhat hard to pick out on conventional imagery, but microwave imagery much more clearly showed a lopsided, westerly weighted structure during the intensification phase. As far as structural defects go, there are certainly worse, but this shear appears to have eroded the structure on the system's eastern side just enough to impinge on the intensification rate enough to keep it from truly going crazy in the extremely favorable thermodynamic environment Eta was located in.

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Another possible factor perhaps preventing Eta from matching its impressive satellite appearance might have been the early onset of eyewall replacement. Like recon data, MW coverage of Eta near peak intensity left something to be desired, but a big blowup of convection did occur on the outer fringes of the CDO around 00Z November 3rd. I suspect this might actually be the "Lobing" phenomenon mentioned earlier in this thread. To me, whenever I see a relatively large lobe of cold convection develop nearer to the periphery of the CDO, I start thinking about eyewall replacement. In this case, the rather (abstract) radar data out of San Andres may indicate that this was around the moment the principal feeder band fully surrounded the core and joined back into itself, forming an outer eyewall. It might even be possible that the convective burst was a direct result of increased convergence where the principal feeder band joined back with itself. The recon mission that investigated Eta shortly thereafter showed early hints of eyewall replacement (particularly in the flight level wind data and rain rates), but the replacement cycle really kicked into high gear in the overnight hours after the plane left.

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It is pretty much indisputable that Hurricane Eta had a pretty much top end thermodynamic environment to work with. Cloud tops near peak intensity were regularly in the CMG to CDG temperature range, the eyewall was enveloped with lightning, and intense mesovorticies were observed within the eyewall. The mesovorticies were so intense that recon actually had to avoid the NW quadrant near peak intensity, which is a talking point in itself. However, while still an intense TC, I believe it is likely that easterly shear and the onset of eyewall replacement limited Eta below its ridiculous IR presentation somewhat. There may be a little room for interpretation given some of the difficulties with properly sampling Eta near peak intensity, but as it stands right now, Eta is certainly one of the most impressive TCs you'll ever see not to breach the SSHWS C5 threshold.

Image

Of course, another issue in itself is how to identify TCs like this remotely and differentiate them from those that more closely match their IR presentation. There may not be an easy answer, but a starting point might be to look for some similar deficiencies to what Eta had, like a somewhat ragged eye, lopsided MW structure, and lobing/other convective irregularities. How they all should be weighted in an intensity estimate...is something that I don't think there is a good answer for at the moment.
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Re: Discussion of Intense Tropical Cyclones

#590 Postby Imran_doomhaMwx » Fri Dec 18, 2020 2:14 am

Amazing srfc obs from Virac station, Catanduanes during STY Goni (Rolly). Max wind speed of 150kts and min SLP in the 920s.

 https://twitter.com/JoshuaCAgar/status/1339757525059530752


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Re: Discussion of Intense Tropical Cyclones

#591 Postby mrbagyo » Fri Dec 18, 2020 4:09 am

Imran_doomhaMwx wrote:Amazing srfc obs from Virac station, Catanduanes during STY Goni (Rolly). Max wind speed of 150kts and min SLP in the 920s.

https://twitter.com/JoshuaCAgar/status/1339757525059530752?s=19



spot on projection wow
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Re: Discussion of Intense Tropical Cyclones

#592 Postby mrbagyo » Tue Jan 05, 2021 10:41 pm

Potential new world record holder (if validated) for lowest land based barometric pressure reading (and there's a huge gap between this and the currently recognized record holder)

 https://twitter.com/JoshuaCAgar/status/1346652215428018177


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Re: Discussion of Intense Tropical Cyclones

#593 Postby MarioProtVI » Thu Jan 07, 2021 7:21 am

With the release of JTWC’s 2019 BT, Fani has been upped significantly to 150 kt.
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Re: Discussion of Intense Tropical Cyclones

#594 Postby aspen » Thu Jan 07, 2021 10:16 am

MarioProtVI wrote:With the release of JTWC’s 2019 BT, Fani has been upped significantly to 150 kt.

I’m surprised they went that high, since Kyarr was only upped to 135 kt and it also had a good argument for Cat 5 status (Dvorak did peak at T#7.0-7.2 and maintain itself around there for some time).
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Re: Discussion of Intense Tropical Cyclones

#595 Postby Weather Dude » Thu Jan 07, 2021 2:03 pm

aspen wrote:
MarioProtVI wrote:With the release of JTWC’s 2019 BT, Fani has been upped significantly to 150 kt.

I’m surprised they went that high, since Kyarr was only upped to 135 kt and it also had a good argument for Cat 5 status (Dvorak did peak at T#7.0-7.2 and maintain itself around there for some time).

Wow I thought Kyarr had the better chance for the upgrade, and I'm very surprised they went that high for Fani. I wonder what evidence they used to justify that? I remember thinking Kyarr had solid evidence for a possible upgrade (as in the Dvorak in your post), but I don't remember thinking the same thing with Fani, let alone 150 kts. Maybe I missed something...
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Re: Discussion of Intense Tropical Cyclones

#596 Postby Meteophile » Thu Jan 07, 2021 4:21 pm

MarioProtVI wrote:With the release of JTWC’s 2019 BT, Fani has been upped significantly to 150 kt.



Well I think they probably got it right (or close). The reason I think that is still the same as in this old tweet (look at my tweet's answer for more details):


 https://twitter.com/Meteophile1/status/1123853985658617856




(the probability of wrongness is high because I'm far from being a meteorologist)
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Re: Discussion of Intense Tropical Cyclones

#597 Postby Imran_doomhaMwx » Thu Jan 07, 2021 11:35 pm

Weather Dude wrote:Wow I thought Kyarr had the better chance for the upgrade, and I'm very surprised they went that high for Fani. I wonder what evidence they used to justify that? I remember thinking Kyarr had solid evidence for a possible upgrade (as in the Dvorak in your post), but I don't remember thinking the same thing with Fani, let alone 150 kts. Maybe I missed something...

Fani was also a candidate for possible cat 5 upgrade in post-analysis. JTWC operationally had a consecutive Dvorak analysis of T7.0 for it, and SATCON also supported a low-end cat 5. Still, I too was surprised that they gave 150kts, but surely, JTWC wouldn't have gone that far without supporting data. Possibly one of the things that would support such intensity is data from the Sentinel SAR.

On May 3 00Z, as Fani was nearing India and already falling from its 150kt peak on May 2 12Z, SAR got a good pass and found max wind speeds of 138kts in the cyclone's SE quadrant. That's already higher than the 135kt peak JTWC gave operationally. ADT and SATCON were not too far either as estimates from these platforms were 130kts at the time of this SAR pass. JTWC set the May 3 00Z intensity to 135kts on the BT (operational: 130kts), which is in the middle of the SATCON/ADT and SAR winds. Considering that Fani's satellite presentation quickly degraded after peaking, and SAR 12hrs later still found a powerful 138kt TC (with some support from Dvorak and SATCON), I think Fani was indeed a solid cat 5.

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Re: Discussion of Intense Tropical Cyclones

#598 Postby mrbagyo » Tue Jan 26, 2021 10:48 am

mrbagyo wrote:Potential new world record holder (if validated) for lowest land based barometric pressure reading (and there's a huge gap between this and the currently recognized record holder)

https://twitter.com/JoshuaCAgar/status/1346652215428018177?s=19


The DOST-ASTI data produced a nice looking pressure trace

Image
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Re: Discussion of Intense Tropical Cyclones

#599 Postby NotoSans » Fri Jan 29, 2021 1:35 am

Lowest SLP recorded in Virac during Goni was 912.1mb.
 https://twitter.com/squirtleinhk/status/1355041225745653760


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Re: Discussion of Intense Tropical Cyclones

#600 Postby Ptarmigan » Sun Jan 31, 2021 12:02 pm

mrbagyo wrote:Potential new world record holder (if validated) for lowest land based barometric pressure reading (and there's a huge gap between this and the currently recognized record holder)

https://twitter.com/JoshuaCAgar/status/1346652215428018177?s=19

In September 14, 2016, when Typhoon Ferdie was hovering over Itbayat Island, the pressure station recorded a barometric pressure of 868.76 hPa (Sea-level equivalent: 877.91 hPa).Data from: Advanced Sciences and Technology Institute pic.twitter.com/S395oNw1XR
-- Joshua C. Agar (@JoshuaCAgar) January 6, 2021


That would be the most intense landfalling tropical cyclone and more so than Super Typhoon Tip. :eek: :cold: :double:

Makes me wonder if there are tropical cyclones that have central pressure of 850 millibars or lower.
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