Discussion of Intense Tropical Cyclones

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Re: Discussion of Intense Tropical Cyclones

#281 Postby tatertawt24 » Sat Feb 17, 2018 2:47 pm

1900hurricane wrote:While looking back at some satellite imagery from Maria '17, I noticed an interesting feature around the time of peak intensity. Just before 00Z September 20th, there was a large and cold convective near the edge of the CDO (still image below, loop here). I'm not sure this phenomenon has a proper name, so for now, I'm going to call it lobing.

Image

Based on recon data, it appears like it might have coincided with a halt in intensification since the previously falling pressure evened out at 909 mb at the 2219Z pass and only varied by a millibar up and down from that number for the next six hours before rising. This lobing phenomenon could possibly be associated with structural changes. Lobing isn't exclusive to Maria '17 either. It appears it has occurred with a number of intense tropical cyclones across multiple basins. Some of the more clear examples are Nepartak '16, Patricia '15, Usagi '13, and Gilbert '88. Patricia '15 and Gilbert '88 each had recon near the time of lobing (near 18Z October 23rd for Patricia and 00Z September 14th for Gilbert), and both cases were similar to the Maria '17 data which showed no appreciable deepening from that time on. Patricia '15 actually began to weaken rapidly, although land interaction may have played a part in that case. Regardless, it may be a good sign to indicate whether an intense tropical cyclone has peaked.


I'm pretty sure I know what you're talking about, but could you circle it on the Maria picture so I can be sure? :lol:
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Re: Discussion of Intense Tropical Cyclones

#282 Postby 1900hurricane » Sun Feb 18, 2018 1:48 am

tatertawt24 wrote:
1900hurricane wrote:While looking back at some satellite imagery from Maria '17, I noticed an interesting feature around the time of peak intensity. Just before 00Z September 20th, there was a large and cold convective near the edge of the CDO (still image below, loop here). I'm not sure this phenomenon has a proper name, so for now, I'm going to call it lobing.

[image removed]

Based on recon data, it appears like it might have coincided with a halt in intensification since the previously falling pressure evened out at 909 mb at the 2219Z pass and only varied by a millibar up and down from that number for the next six hours before rising. This lobing phenomenon could possibly be associated with structural changes. Lobing isn't exclusive to Maria '17 either. It appears it has occurred with a number of intense tropical cyclones across multiple basins. Some of the more clear examples are Nepartak '16, Patricia '15, Usagi '13, and Gilbert '88. Patricia '15 and Gilbert '88 each had recon near the time of lobing (near 18Z October 23rd for Patricia and 00Z September 14th for Gilbert), and both cases were similar to the Maria '17 data which showed no appreciable deepening from that time on. Patricia '15 actually began to weaken rapidly, although land interaction may have played a part in that case. Regardless, it may be a good sign to indicate whether an intense tropical cyclone has peaked.


I'm pretty sure I know what you're talking about, but could you circle it on the Maria picture so I can be sure? :lol:


Image
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Re: Discussion of Intense Tropical Cyclones

#283 Postby tatertawt24 » Sun Feb 18, 2018 2:13 pm

1900hurricane wrote:
tatertawt24 wrote:
1900hurricane wrote:While looking back at some satellite imagery from Maria '17, I noticed an interesting feature around the time of peak intensity. Just before 00Z September 20th, there was a large and cold convective near the edge of the CDO (still image below, loop here). I'm not sure this phenomenon has a proper name, so for now, I'm going to call it lobing.

[image removed]

Based on recon data, it appears like it might have coincided with a halt in intensification since the previously falling pressure evened out at 909 mb at the 2219Z pass and only varied by a millibar up and down from that number for the next six hours before rising. This lobing phenomenon could possibly be associated with structural changes. Lobing isn't exclusive to Maria '17 either. It appears it has occurred with a number of intense tropical cyclones across multiple basins. Some of the more clear examples are Nepartak '16, Patricia '15, Usagi '13, and Gilbert '88. Patricia '15 and Gilbert '88 each had recon near the time of lobing (near 18Z October 23rd for Patricia and 00Z September 14th for Gilbert), and both cases were similar to the Maria '17 data which showed no appreciable deepening from that time on. Patricia '15 actually began to weaken rapidly, although land interaction may have played a part in that case. Regardless, it may be a good sign to indicate whether an intense tropical cyclone has peaked.


I'm pretty sure I know what you're talking about, but could you circle it on the Maria picture so I can be sure? :lol:


Image


Yeah, it seems like it's something that happens when the storm can't bomb out much more than it already has. Maybe a case of the storm trying to grow even stronger (as evident by shooting up even colder cloud tops), but for whatever reason, just not being able to intensify any further.
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Re: Discussion of Intense Tropical Cyclones

#284 Postby 1900hurricane » Mon Mar 05, 2018 9:03 am

I think it might be more structural than anything. When looking at microwave imagery near the time of lobing, Maria '17 (below), Nepartak '16, and Patricia '15 all had swaths of significantly cold brightness maximums indicative of ice scattering in intense thunderstorm activity in developing outer eyewalls. WIth Usagi '13, it's a little less clear since there was a gap in microwave coverage near the time of the peripheral blow up, but 37 GHz imagery from slightly beforehand does indicate at least the beginnings of an outer eyewall structure, although it appears to have been disrupted in later passes.

Image
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Re: Discussion of Intense Tropical Cyclones

#285 Postby Chris90 » Wed Apr 11, 2018 7:48 pm

https://www.google.com/url?sa=t&source= ... EKiwCsO8k3

The above is a link to an interesting journal article I read yesterday. I'm posting this on my phone, so if for some reason the link doesn't work, please let me know so I can fix it.

The article is about measurements they took during Harvey's landfall using the DOW (Doppler-on-wheels.) They were studying eyewall wind features such as eyewall mesovortices and tornado scale vortices. I thought the article and the data they collected was fascinating, as this is something we've heard about in relation to intense tropical cyclones quite a bit, and this was the first time they've collected this kind of data on it. Andrew is the first storm that comes to mind, as it was theorized that mini-swirls caused the extreme wind damage observed during his passage through South Florida. Another storm that comes to mind is Charley and the infamous video taken at the gas station. I know I read it was a possibility that a mini-swirl like feature was responsible for the brief duration burst of intense, violent winds.
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Re: Discussion of Intense Tropical Cyclones

#286 Postby supercane4867 » Sun Jun 10, 2018 9:34 am

Some informative tweets from Ryan Maue yesterday:

 https://twitter.com/RyanMaue/status/1004940113829421057




 https://twitter.com/RyanMaue/status/1004945285007671296




 https://twitter.com/RyanMaue/status/1005118422370455558




 https://twitter.com/RyanMaue/status/1005253034618867712




 https://twitter.com/RyanMaue/status/1005256146427498497




 https://twitter.com/RyanMaue/status/1005257436524138496





Looking at HURSAT data, I'd say about 50 percent of EPAC hurricanes in the EPHC era were underestimated to some degree.

Kiko 1983 is one of the most evident missing CAT5s I've found, with 18 hours of DT7.0 satellite signature on both AVHRR and GOES imagery. Visible presentation justifies CAT5 rating as well. I estimate 145kt for this one, while the best track has it at 125kt.

Image

Image

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Image


Hurricane Norbert in the following year is another one. Looks at least 135kt while the best track is 115kt low-end CAT4.

Image

Image
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Re: Discussion of Intense Tropical Cyclones

#287 Postby djones65 » Sun Jun 10, 2018 9:24 pm

In my opinion, the "lobing," that 1900 is talking about is simply a symptom of eyewall replacement. As the inner core dies, the greatest convergence reorganizes downwind of upper level winds. In case of Maria although shear was very light, greatest divergence was southeast of the eye. Therefore, the most significant convection would develop in that quadrant. As the eyewall replacement cycle continued the "lobing" became less pronounced as the outer eyewall began to contract.
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Re: Discussion of Intense Tropical Cyclones

#288 Postby djones65 » Sun Jun 10, 2018 9:30 pm

To reiterate, if a significant tropical cyclone suddenly develops this "lobing" phenomenon, it is very possibly a sign of eyewall replacement ongoing. Especially when the "lobing" convection is significantly deeper than the previous convection. If that makes sense. So, this is simply just more evidence of attempting to predict eyewall replacement cycles in situations in which we don't have radar or microwave imagery available to confirm. Obviously, when the ERC begins strengthening temporarily ceases until or if a new inner core reestablishes itself. So this is another "tool" to monitor when looking at possible eyewall replacements or intensity forecasts especially when hurricanes are approaching land.
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Re: Discussion of Intense Tropical Cyclones

#289 Postby euro6208 » Thu Jun 14, 2018 8:23 am

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Re: Discussion of Intense Tropical Cyclones

#290 Postby euro6208 » Thu Jun 14, 2018 8:25 am

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Re: Discussion of Intense Tropical Cyclones

#291 Postby euro6208 » Thu Jun 14, 2018 8:26 am

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Re: Discussion of Intense Tropical Cyclones

#292 Postby euro6208 » Thu Jun 14, 2018 8:26 am

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Re: Discussion of Intense Tropical Cyclones

#293 Postby euro6208 » Thu Jun 14, 2018 8:30 am

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Re: Discussion of Intense Tropical Cyclones

#294 Postby euro6208 » Thu Jun 14, 2018 8:32 am

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Re: Discussion of Intense Tropical Cyclones

#295 Postby Shell Mound » Thu Jun 14, 2018 11:16 am

 https://twitter.com/RyanMaue/status/1006373014047547392



 https://twitter.com/RyanMaue/status/1006375400543485952



 https://twitter.com/RyanMaue/status/1006375676012789761



 https://twitter.com/RyanMaue/status/1006376885578862594



 https://twitter.com/RyanMaue/status/1006247710394060802



 https://twitter.com/RyanMaue/status/1006248140855529473



 https://twitter.com/RyanMaue/status/1006232300974231552



 https://twitter.com/RyanMaue/status/1006237449880784896



 https://twitter.com/RyanMaue/status/1006191303397462016



 https://twitter.com/RyanMaue/status/1006193375882764289



 https://twitter.com/RyanMaue/status/1006185627254247425



 https://twitter.com/RyanMaue/status/1005848989072351234



 https://twitter.com/RyanMaue/status/1005266477291892736



 https://twitter.com/RyanMaue/status/1005268202555891712



 https://twitter.com/RyanMaue/status/1005253034618867712



 https://twitter.com/RyanMaue/status/1005254057810939905



 https://twitter.com/RyanMaue/status/1005256146427498497



 https://twitter.com/RyanMaue/status/1005257436524138496



 https://twitter.com/RyanMaue/status/1005241855523676160



 https://twitter.com/RyanMaue/status/1005238404219654147



 https://twitter.com/RyanMaue/status/1005239661550284800



 https://twitter.com/RyanMaue/status/1004962138723684352



 https://twitter.com/RyanMaue/status/1004973261350940672



 https://twitter.com/RyanMaue/status/1004966236663447552



 https://twitter.com/RyanMaue/status/1004953313694175233



 https://twitter.com/RyanMaue/status/1004945285007671296



 https://twitter.com/RyanMaue/status/1004943138937540608



 https://twitter.com/RyanMaue/status/1004940113829421057



 https://twitter.com/bankingoffgreen/status/1004940474531090432



 https://twitter.com/RyanMaue/status/1004929440206467073



 https://twitter.com/RyanMaue/status/1004926123044737024



 https://twitter.com/RyanMaue/status/1004922114401538048



 https://twitter.com/RyanMaue/status/1004915341720539136



 https://twitter.com/RyanMaue/status/1004918418796105733



 https://twitter.com/RyanMaue/status/1004880116776931328



 https://twitter.com/MattGross87/status/1004887084308598784



 https://twitter.com/RyanMaue/status/1004860002853638144


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Re: Discussion of Intense Tropical Cyclones

#296 Postby TheAustinMan » Fri Jun 15, 2018 11:36 am

One thing that I've noticed that might need to be considered is that, from what I've seen, infrared data from polar orbiters like the AHVRR instrument seem to run a bit colder (and the sea surface much warmer) than data from their geostationary counterparts. As one example, compare this AVHRR infrared image of Hurricane Kenneth in 1993 with this this GOES infrared image of Kenneth from the same time. There is, of course, a difference in clarity, but the differences between the two images are a bit more drastic than one might expect from a simple difference in resolution. In the AVHRR image there's an impressive cold medium gray (CMG) ring around a warm medium gray (WMG) eye, with a nearly complete and thick cold dark gray (CDG) ring, information that might tell an aggressive analyst to rate the system a T7.5 for 155 knots. On the other hand, the GOES image shows only light gray (CMG) cloudtops around the eyewall, and even then they don't seem to be thick enough to be considered in calculating the eye number in a Dvorak analysis; an analyst may look at this and classify the system as a T6.5 for 125 knots. The best track data for the system has it at 125 knots at the time.

One might chalk this up to a difference in viewing angle. That's a great guess, but the answer might not be as clear cut as that. In the AVHRR image above, we see that the storm passed well within the scanning area of the polar-orbiting satellite, meaning that the orbiter went almost directly overhead, resulting in a low zenith angle (alternatively, the distance from the storm to the spot directly beneath the satellite is small). By comparison, the GOES satellite, in a stationary position at 135*W, would have a larger zenith angle (alternatively, the distance from the storm to the spot directly beneath the satellite is larger). However, one would expect that a larger zenith angle would produce cooler cloud tops due to the effects of limb cooling (zenith angles explained briefly on page 65 in this presentation (PDF) and a little bit on limb cooling explained in this presentation (PDF)).

One may also point to a potential difference in band sensitivities, but even this is a bit ambiguous. The choice band for infrared cloud-top imagery on AVHRR has been band 4, which is sensitive to wavelengths of 10.3 microns to 11.3 microns for a central wavelength of 10.8 microns. On the other hand, the choice band for infrared cloud-top imagery on the last generation of GOES was band 4, sensitive to wavelengths of 10.2 microns to 11.2 microns for a central wavelength of 10.7 microns (PDF); that means there wasn't much difference between the two. Ffor an illustration, compare this clean IR (10.3 microns) image of TD 04E with this traditional longwave IR (11.2 microns) image of TD 04E. There are some slight differences, but certainly not the drastic ~ 5°C difference implied from the first two images of Kenneth, and 5°C can make a lot of difference in the world of satellite intensity estimation.

This isn't just something that ought to be considered with old imagery from the 1980s and 1990s, either. Compare this GOES-13 infrared image of Hurricane Irma with this image from the F17 polar orbiter, taken within 5 minutes of eachother. There are just a few smidgens of cloud tops that dip below -75°C, while the bulk of the eyewall is around -70°C, forming that large white band you see. The eye there is about +18°C, I would estimate. However, pop open the AVHRR image and wow, where did all those grays in the eyewall come from? In the F17 image, cloud tops are pushing under -80°C and we now have a nearly complete ring of sub -75°C cloud tops. Meanwhile, the eye in the polar orbiter is much warmer, at around +24°C!

Knowing what we know about tropical cyclones today, a lot of cyclones outside of the Atlantic in the 20th century have definitely been grossly underestimated. A lot of that can be gleaned from low-resolution geostationary images, in addition to other supporting evidence. But there might be a little catch, a tiny asterisk if you will, when considering some of the high resolution polar orbiting imagery we have. Food for thought.
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Re: Discussion of Intense Tropical Cyclones

#297 Postby Ptarmigan » Sun Jul 01, 2018 7:40 pm

Looking at these satellite images of tropical cyclones, they clearly look very intense, especially in the Southwest Pacific. If the central pressure was actually measured, some could be more intense than Super Typhoon Tip.
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Re: Discussion of Intense Tropical Cyclones

#298 Postby euro6208 » Tue Jul 03, 2018 8:16 am

Ptarmigan wrote:Looking at these satellite images of tropical cyclones, they clearly look very intense, especially in the Southwest Pacific. If the central pressure was actually measured, some could be more intense than Super Typhoon Tip.


Tip is old news. The only reason why it's still up is because the WPAC lost it's recon.
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Re: Discussion of Intense Tropical Cyclones

#299 Postby 1900hurricane » Thu Aug 02, 2018 10:59 pm

I have also noticed that from the AVHRR dataset, although it varies from satellite to satellite, storm to storm, and pass to pass. My go to for difference between temps for AVHRR vs geostationary is actually Gilbert '88. The NOAA-9 pass from 2120Z September 13th has a CDO with basically full cold dark grey coverage (below, top) while the 21Z GOES-7 image still shows a very intense system, but with only cold medium grey CDO coverage rather than cold dark grey.

Image

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Re: Discussion of Intense Tropical Cyclones

#300 Postby 1900hurricane » Thu Aug 02, 2018 11:02 pm

Also, I love to embed Twitter posts, but there is a ton of them on this page. It actually makes my pretty fast internet connection work a little bit, so the primary function pf this post is to help turn the thread over to the next page.

It is worth noting that many of those storms have actually been mentioned in this thread already though.
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