Discussion of Intense Tropical Cyclones

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Re: Discussion of Intense Tropical Cyclones

#321 Postby supercane4867 » Tue Sep 11, 2018 12:40 pm

EquusStorm wrote:Oh lordy, Camille landfall intensity debates. Now that's a can of worms.

Not a certified hurricane expert here by any means, but as someone very familiar and experienced with trees and their structure, you do not have whole undamaged stands of Pinus elliotti and Pinus palustris after 220mph wind gusts. You just don't. It is pretty much physically impossible. EF3-strength three second gusts in the 140 to 150 range easily snaps 95% of even thicker Pinus taeda stems, though of course rapid acceleration in tornadic winds is much more likely to snap trees than gradual hurricane acceleration. Category three Ivan caused devastating loss to longleaf and slash pine stands well inland, but the photos I see from Camille directly from the coast where winds were supposedly vastly stronger than Ivan's show mostly standing pines. Andrew's tree and structural damage is trademark CLASSIC category five wind damage, as is Irma's in the Caribbean although tree species distribution there is vastly different. Those two storms were very similar in suggesting extreme winds; however all of the Camille damage I've seen in photos suggests much lower winds (admittedly more significant than Katrina's though) but extreme surge damage.

Camille was a violent monster over the Gulf and its landfall pressure was frightfully low, and I'd say probably only Rita and Katrina come close as being the most impressive northern Gulf hurricane on record, but photos don't lie; unless someone has proof of obliterated pine stands and non-surge related structural damage suggesting winds over 170-180mph, I can't be convinced Camille was as strong as has been long suggested at landfall. Rednecks claiming it has to be because they heard the wind go woosh and their grandpa insisted winds were 220mph without any proof is, scientifically, garbage, more fit to a book on experiences than actual record, and if the article is anything to go by, I'd only trust legit officially recorded winds to estimate landfall intensity. I don't for a minute believe that higher winds weren't recorded because the instruments failed (unless legitimately verified that this happened) if whole stands of pines survived the lashing nearby. If we take unproven anecdotes as intensity facts, then we have to lower the pressure of the 1935 Labor Day cane (which, those who claim the Camille intensity debate is an effort to downplay past storms should realize has been dramatically intensified in recent analysis and was clearly much stronger than Andrew OR Irma) to 880mb, as a barometer thrown into the sea and never recovered supposedly measured this.

Of course maybe tree damage was much more severe right at the core eastern eyewall and I could be wrong... but I kinda doubt it. Very intense hurricane at landfall, perhaps by far strongest in MS history? Absolutely. Possible marginal low end Cat 5? Possible, but available photos make that debatable. High-end 180-190 sustained? Not even a chance given measured and photographed intensity and damage.


I'm not going to debate with anyone, but I have to respectfully disgree with your point. I don't think it's pratical to assume the intensity of hurricanes based upon damage photos rather than measured data, especially for the storms in early or non-satellite era when most avaliable photos were of poor quality. Recon, radar, and ground measurement during the time of Camille apporaching the coast have provided a detailed observation for the evlution of the storm. Unlike Katrina, Camille had successfully complete a EWRC before landfall and was in the process of rapidly restrengthing. Katrina's landfall pressure was in the 920s but winds were at CAT3 due to an incompelete EWRC, but that's not the case in Camille. The landfalling pressure of 900mb in a strengthening hurricane would almost certainly corrspondes to CAT5 windspeed. I belive the intensity and structual evlution of Camille before landfall is very similar to Andrew, which had completed an EWRC only hours prior to landfall. According to the reanalyzed best track, Andrew made landfall on Berry Island, Bahamas at 24/01z as a 931mb/130kt hurricane. A combination of EWRC and land interaction caused Andrew weakened to 935-940mb, followed by a 15mb pressure drop while traversing over Gulf stream. The windspeed increased from 130kt to 145kt in three hours during that pressure drop, and Andrew made landfall on SFL at 24/09z with an intensity of 922mb/145kt. Renalysis data suggest Camille went through a similar pressure drop - 20mb decrease in 10 hours before landfall. I'd think that the increase in windspeed should be also 15kt or higher during the period. The intensity of Camille during EWRC was set to 920mb/135kt, a 20mb pressure drop since that time should raise the windspeed to at least 150kt for landfall, which is the analyzed landfall intensity by NHC.

Remember, the intensity of tropical cyclone is based on sustained wind alone, but wind gusts is an important factor to the degree of damage on buildings and trees. A CAT4 or CAT3 could have mesovorticies that produce wind gusts well into CAT5 range. Topography enhancement can also produce stronger winds unrepresentative to the actual intensity of the storm. It's much harder to find extreme wind damage on a flat terrain like the Gulf coast than you would see if a hurricane hits a mountainous island.

Excerpt from Camille reanalysis:
This central pressure of 900 mb—a roughly 20-mb decrease in the 10 h since the last aircraft data—shows Camille was strengthening at landfall, possibly because of the end of the ERC. Brown et al. (2006) suggest maximum sustained winds at landfall of 148 kt using the standard relationship or 155 kt using the intensifying subset north of 25°N. Given the competing factors of a tiny RMW of approximately 6–8 n mi and a moderate forward speed of 15 kt, but a very low pressure of the outer closed isobar of 1004 mb, an intensity of 150 kt is reanalyzed for the time of landfall (a graph of the previous and reanalyzed best-track intensities is provided in Fig. 7). The 150 kt at landfall show Camille as a category 5 hurricane at landfall in Mississippi. This intensity assessment confirms the original indication of Camille as a category 5 striking the United States (Hebert and Taylor 1978).

http://www.aoml.noaa.gov/hrd/Landsea/ki ... s-2016.pdf
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Re: Discussion of Intense Tropical Cyclones

#322 Postby EquusStorm » Tue Sep 11, 2018 12:54 pm

All fair points, and I definitely don't discount that Camille was perhaps a lower end cat 5 at landfall; mainly the post is a rant about those who firmly believe the obviously ridiculous sustained 190/gusts to 220 at landfall which isn't supported by any land data that I have ever known to be realistically verified and peer-reviewed. 160, very possibly, but 190-200, not even a chance. Unlike building quality, tree damage is objective and I am more likely to believe that over incomplete data, but I do think that damage was probably much more severe in mesovortices and right in the northeastern eyewall. Just saying that category five winds weren't super widespread anywhere but right near the core, if they happened at all; it is absolutely impossible to have whole undamaged stands of slash and longleaf pine with 200 mph winds. If there were no measured winds on land that high, I would be loathe to include estimates and extrapolations when dealing with a record that important. That there are photographs available of mostly undamaged gas station canopies (usually obliterated at 150+ mph) and mostly undamaged wood frame houses with roofs intact (usually unroofed at 140+ mph) near Pass Christian alongside perfectly undamaged still-standing isolated spindly pines, near the heart of where the most intense winds should have been assuming normal storm structure, just make me completely unable to believe winds were anywhere near as high as reported; reports of which there are no surviving official surface measurements of. Again, I believe observed evidence and damage more than extrapolations and estimates, but that's just my personal view and certainly doesn't necessarily make me right.

I also don't really believe the wind/pressure relationships are consistent in extremely intense storms undergoing rapid structural changes and fluctuations; Katrina's 125/920 made that pretty clear, but Camille's extremely low pressure (assuming instrument calibration was accurate) is perhaps one of the only compelling arguments that it was at least a high end 4 because <910 is pretty unprecedented in anything that's not a category five except in Wilma's case. Still, wind occasionally lags well behind pressure in rapid intensification and re-intensification, so even with a pressure that low, it wouldn't necessarily 100% correlate with the normal w/p relationship, though no doubt with a pressure that low, still close to category five winds if not slightly over that threshold. That all said, I know more about trees than the machinations of high end landfalling hurricanes, so I defer to the experts on the objective things :ggreen:
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Re: Intense Tropical Cyclone Discussion

#323 Postby xtyphooncyclonex » Fri Sep 14, 2018 3:21 am

Wanted to point this out:

supercane4867 wrote:Here's a classic example of how IR imagery can be misleading, and with recon support

Typhoon Jangmi when recon measured 140kt and 906mb

http://i.imgur.com/i0e6tyT.jpg


Hurricane Katrina when recon measured 150kt and 902mb

http://i.imgur.com/yPZN3Du.jpg

They are similar in both size and structure but Katrina is confirmed to be the stronger one despite looks a lot weaker on satellite.
Higher latitude and background pressure in GOM is likely the reason in this case
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Re: Discussion of Intense Tropical Cyclones

#324 Postby 1900hurricane » Mon Sep 24, 2018 7:22 pm

Here's another talking point. In Irma '17, there was a well documented unusual eyewall replacement progression (or lack thereof) September 5th-6th where concentric eyewalls appeared to develop, but instead of having the outer eyewall replace the inner eyewall, the outer eyewall apparently faded/melded into the inner eyewall. It also appears to have happened with Winston '16 and may be happening currently with Super Typhoon Trami (tweet below). To be honest, I have no idea what causes this apparently very rare eyewall progression, but perhaps something can be found in the Irma '17 data since it is by far the best documented example.

 https://twitter.com/1900hurricane/status/1044351613547278336


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Re: Discussion of Intense Tropical Cyclones

#325 Postby Chris90 » Mon Sep 24, 2018 7:48 pm

I have no education in meteorology, and I'm not particularly knowledgeable on inner core dynamics, so these are some random guesses that those of you with more knowledge may be able to blow massive holes in, and if you can, please do. I'm here to learn more because I find tropical weather fascinating.

But I wonder if the eyewall meld is a combination of favorable factors with a tight pressure gradient. We've seen before where eyewall replacement cycles broaden the pressure gradient thereby increasing the area of maximum wind, but also simultaneously bringing the max wind down.
In something like Irma of '17, I'm wondering if the favorable factors first led to an ERC having an easier time being effective. Storms have struggled before with dry air and shear disrupting the ERC process therefore they have a harder time completing. Irma was working with favorable factors therefore the ERC had an easier time.
Second, I wonder if the ridge Irma was moving under was strong enough that maybe it prevented the pressure gradient from broadening too much? Maybe the pressure gradient had a harder time broadening due to the ridge and it caused a dynamic where the outer eyewall then melded into the inner due to maybe some type of forcing caused by the ridge?
As I said, I may be way off, so if those with more knowledge know I'm wrong, feel free to prove me wrong. I have no formal training, so I won't be offended. :D
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Re: Discussion of Intense Tropical Cyclones

#326 Postby NotoSans » Mon Oct 08, 2018 10:42 am

I have seen a lot of people mentioning the minimum SLP of 899.2 mb recorded during Rammasun'14, and I'd like to provide some additional information regarding this observation.

Below is the radar imagery when the above-mentioned value was recorded. The red triangle represents the exact location of the automatic weather station. It can be seen that the minimum SLP was recorded when the station was located at the edge, but not the center, of the eye.
Image

The pressure trace shows that the minimum SLP was recorded at 13:21 local time. However, the SLP was at 908.3 mb one minute prior at 13:20, which suggested a pressure change of 9.1 mb in one minute. As a comparison, Guiuan, when affected by the eyewall of Haiyan, recorded a pressure change of around 1 mb per minute. Moreover, the SLP recorded at 13:30 and 13:40, when the center of the eye was moving over the automatic weather station, were 907.0 mb and 914.6 mb respectively, significantly higher than the minimum value.

From the above data, I would argue that the automatic weather station was affected by an eyewall mesovortex when the minimum SLP was recorded, resulting in an abnormally sharp pressure change. It's likely that the minimum SLP of 899.2 mb was not representative of the overall circulation of Rammasun. If this value is discounted, the best estimate of the central pressure of Rammasun will likely be 905 mb.

Applying the KZC wind-pressure relationship with the following inputs: POCI of 1000 mb based on JMA surface weather chart, forward motion of 14 kt based on JMA best track, and average 34-kt wind radii of 115 nm converted from JMA's estimated wind radii using the regression analysis conducted by 1900hurricane, the estimated maximum intensity is 150 kt for Rammasun.
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Re: Discussion of Intense Tropical Cyclones

#327 Postby CrazyC83 » Fri Oct 12, 2018 11:54 pm

Back to the Camille intensity debate, now that we have all seen a NGOM high intensity storm intensify right up to landfall, I think we can close the discussion and accept the reanalysis.
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Re: Discussion of Intense Tropical Cyclones

#328 Postby EquusStorm » Sat Oct 13, 2018 1:09 pm

Pff... yes, but I still wish any damage from winds that high on land had been properly documented. Would've solved the debate a long time ago.
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Re: Discussion of Intense Tropical Cyclones

#329 Postby Abdullah » Sat Oct 13, 2018 3:15 pm

Where are you all getting these archived images from?
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Re: Discussion of Intense Tropical Cyclones

#330 Postby djones65 » Sat Oct 13, 2018 11:26 pm

Remember, especially with Camille... we have so very few surface observations other than pressure near the eye... And there was at least 24 foot storm surge with wave action on top of that... I am certain it must have mitigated some of the tree damage that is normally seen in areas in which the storm surge wasn't nearly so significant. I personally believe after Michael that Camille very well may have been 150 knots as investigated.
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Re: Discussion of Intense Tropical Cyclones

#331 Postby Hammy » Sun Oct 14, 2018 4:09 am

Abdullah wrote:Where are you all getting these archived images from?


It looks like most of them are from NRL and RAMMB.

https://199.9.2.143/tcdat/ or https://www.nrlmry.navy.mil/TC.html (1998+)
http://rammb.cira.colostate.edu/products/tc_realtime/season.asp?storm_season=2018 (2006+)

I've been wondering myself where the earlier ones are coming from.
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Re: Discussion of Intense Tropical Cyclones

#332 Postby 1900hurricane » Wed Oct 31, 2018 1:46 am

I'm getting many images from systems that predate the NRL and RAMMB directories from HURSAT.
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Re: Discussion of Intense Tropical Cyclones

#333 Postby SconnieCane » Wed Oct 31, 2018 5:49 am

Sooooooo...who makes the cut this year? Mangkhut, Yutu, possibly Walaka IMO. Michael was clearly in the upper echelon as CONUS landfalls go but that doesn't say much for how it stacks up in terms of global TC intensity.
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Re: Discussion of Intense Tropical Cyclones

#334 Postby Buck » Fri Nov 02, 2018 8:54 am

Surely there is a lot of data and observations from Yutu's Mariana landfall?
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Re: Discussion of Intense Tropical Cyclones

#335 Postby 1900hurricane » Thu Nov 15, 2018 6:41 pm

NotoSans wrote:I have seen a lot of people mentioning the minimum SLP of 899.2 mb recorded during Rammasun'14, and I'd like to provide some additional information regarding this observation.

Below is the radar imagery when the above-mentioned value was recorded. The red triangle represents the exact location of the automatic weather station. It can be seen that the minimum SLP was recorded when the station was located at the edge, but not the center, of the eye.
https://i.imgur.com/qK6rfxD.png

The pressure trace shows that the minimum SLP was recorded at 13:21 local time. However, the SLP was at 908.3 mb one minute prior at 13:20, which suggested a pressure change of 9.1 mb in one minute. As a comparison, Guiuan, when affected by the eyewall of Haiyan, recorded a pressure change of around 1 mb per minute. Moreover, the SLP recorded at 13:30 and 13:40, when the center of the eye was moving over the automatic weather station, were 907.0 mb and 914.6 mb respectively, significantly higher than the minimum value.

From the above data, I would argue that the automatic weather station was affected by an eyewall mesovortex when the minimum SLP was recorded, resulting in an abnormally sharp pressure change. It's likely that the minimum SLP of 899.2 mb was not representative of the overall circulation of Rammasun. If this value is discounted, the best estimate of the central pressure of Rammasun will likely be 905 mb.

Applying the KZC wind-pressure relationship with the following inputs: POCI of 1000 mb based on JMA surface weather chart, forward motion of 14 kt based on JMA best track, and average 34-kt wind radii of 115 nm converted from JMA's estimated wind radii using the regression analysis conducted by 1900hurricane, the estimated maximum intensity is 150 kt for Rammasun.

Further supporting this stance is a sharp pressure drop recorded by Josh Morgerman of iCyclone near the edge of the eye of Hurricane Willa. While re-entering the eyewall, a very sharp pressure drop was recorded on one of his devices, which coincided with very strong winds observed by those at that location. Such observations certainly support the presence of intense mesocyclones near the edge of some TC eyes first hypothesized by Dr. Fujita in Hurricane Andrew '92.

 https://twitter.com/iCyclone/status/1059091407556685824



 https://twitter.com/iCyclone/status/1059096760117714944


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Re: Discussion of Intense Tropical Cyclones

#336 Postby 1900hurricane » Tue Nov 20, 2018 4:16 pm

SconnieCane wrote:Sooooooo...who makes the cut this year? Mangkhut, Yutu, possibly Walaka IMO. Michael was clearly in the upper echelon as CONUS landfalls go but that doesn't say much for how it stacks up in terms of global TC intensity.

I think Mangkhut, Yutu, and maybe Kong-rey are probably the strongest of the NH season, but there have been quite a number of higher end systems this year. JMA has warned on the most violent typhoons (their equivalent to a category 5) in a single season this year. East of the International Date Line, the Pacific has seen three additional category 5s with an argument for a fourth and broken their seasonal ACE record by virtue of the number of quality systems. Even a suppressed/subtropically oriented NATL offered up the intense Hurricane Michael, which itself could possibly a postseason category 5 upgrade. Every single NH basin is above their seasonal ACE averages.

The ones that particularly intrigue me though is this trilogy of Mangkhut, Kong-rey, and Yutu. All three had SATCON peaks of at least 160 kt, with Mankhut and Yutu having two such peaks (although Yutu's second SATCON peak is probably a little inflated and not actually representative of a 160 kt system due to a poor RMW estimate on an AMSU pass). Interestingly enough though, Mangkhut's first peak is the only such of these that didn't feature a CDO of primarily BD CMG or colder. The system had a very large diameter white CDO around a >20ºC eye, but very much lacked the colder tops associated with T7.5+ systems. A comparison of the IR presentation of the system at this peak on September 11th compared to Yutu's first peak on October 24th can be seen below, respectively.

Image

Image

Using traditional IR intensity estimation like the Dvorak Technique and ADT, Yutu clearly appears the stronger. However, SATCON actually slightly favors Mangkhut in this case, and most of the microwave intensity estimates actually overwhelmingly do. While data was in fairly good agreement with Yutu of an intensity of 155-160 kt, Mangkhut's intensity estimates have quite a bit more spread. Why is that? Honestly, I don't have a good answer. I can glean this though. Cloud top temps, while certainly showing a strong correlation to tropical cyclone intensity, is probably not the end-all be-all of TC intensity estimation in high end and extreme systems.

*EDIT: here's the SATCON graphs for reference.

Image

Image
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Re: Discussion of Intense Tropical Cyclones

#337 Postby Hayabusa » Thu Nov 22, 2018 7:30 pm

Pacific Ocean typhoons could be intensifying more than previously projected

Changes to the uppermost layer of Earth's oceans due to rising temperatures are likely causing an increase in intense Pacific Ocean typhoons, suggesting strong typhoons may occur more frequently than scientists project in the coming decades, according to new research.

The deepening of the ocean mixed layer is just one of many substantial changes to atmospheric and ocean circulations that have occurred in the western North Pacific since 2000 as a result of climate change, according to the researchers. Deepening of the ocean mixed layer is likely the major reason for the sudden increase in the proportion of intense typhoons in 2001, Wu said.
Because previous studies have not accounted for ocean mixed layer depth in their projections, the authors conclude that future typhoons in the North Pacific may be increasingly intense, and to an even greater degree than previously thought.

"Previous studies have focused mainly on the role of sea surface temperature in changing typhoon intensity," Wu said. "But they did not account for ocean mixed layer depth as we have, which is why we think that those projections might have underestimated the increase in typhoon intensity."


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Re: Discussion of Intense Tropical Cyclones

#338 Postby 1900hurricane » Sat Dec 22, 2018 9:59 pm

While I'm not dismissing any affects climate change may be playing, I think more context is needed whenever typhoons of today are compared to typhoons of the past. Based on a personal unofficial reanalysis project I have been working on, I think it is very likely that intensity estimates for intense typhoons in the 1970s and 1980s are systematically too low due to a large reliance on the AH77 WPR. Below, I have a table of JTWC's 155 kt and up systems from 1978 to 1985 compared to my findings. In those eight years, I believe the number of such systems should be increased from 2 to 14. There really weren't many borderline cases either; only Vera '79 and Irma '81 failed to have a pressure measured below 900 mb.

Image
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Re: Discussion of Intense Tropical Cyclones

#339 Postby TyphoonNara » Sun Dec 23, 2018 9:58 am

1900hurricane wrote:While I'm not dismissing any affects climate change may be playing, I think more context is needed whenever typhoons of today are compared to typhoons of the past. Based on a personal unofficial reanalysis project I have been working on, I think it is very likely that intensity estimates for intense typhoons in the 1970s and 1980s are systematically too low due to a large reliance on the AH77 WPR. Below, I have a table of JTWC's 155 kt and up systems from 1978 to 1985 compared to my findings. In those eight years, I believe the number of such systems should be increased from 2 to 14. There really weren't many borderline cases either; only Vera '79 and Irma '81 failed to have a pressure measured below 900 mb.

Image


It is also important to note that in the 1970s and 1980s, JTWC's recon planes were unable to measure wind speed in a typhoon directly, and wind speeds were indirectly estimated from the measured central pressure. However, as JTWC used a wind/pressure relationship that is ridiculously low (like 170kts correspond to 850-860mb). Therefore, many storms, in terms of wind speed, were underestimated. It is sad to see that even with recon, WPac storms are still underestimated. :(
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Re: Discussion of Intense Tropical Cyclones

#340 Postby NotoSans » Sun Dec 23, 2018 12:48 pm

One possible approach to re-analysis is to study the relationship between recon-measured central pressure and FT/CI numbers estimated by the Dvorak technique. After that, we could use the KZC wind-pressure relationship to obtain wind speed estimates and possibly re-formulate the Dvorak Table. This is a very demanding project though.
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