Discussion of Intense Tropical Cyclones

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Re: Discussion of Intense Tropical Cyclones

#241 Postby BYG Jacob » Sat Nov 11, 2017 9:22 pm

euro6208 wrote:
galaxy401 wrote:
euro6208 wrote:Been reading alot about these Saffir–Simpson scale, Atlantic p/w, Atkinson-Holliday, and Schloemer equation ETC. What are those? Estimations....Only recon reveals the truth as seen in the Atlantic and loner Patricia.


You know, by all those posts you have made about Patricia in the last couple years, are you perhaps jealous that a storm as strong as Patricia spawned in an area other then the WPAC?


tolakram wrote:Stay on topic please. If you don't have anything new to say OR your reply is about another poster then please do not post. This thread should be a discussion, not a wish list.


Thanks Tolakram.

Just stating the fact that Patricia's have been occurring in the WPAC but with no recon. Now back to topic.

You have no way of knowing that
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Re: Re:

#242 Postby 1900hurricane » Sun Nov 12, 2017 10:04 pm

xtyphooncyclonex wrote:
Hurricaneman wrote:These pressures are my opinion based on if recon had gone in
Typhoon Haiyan 872
Typhoon Tip 870
Typhoon Gay 865
Typhoon Angela 868
Typhoon June 865 {dropsonde was 875 but in the eyewall
Tropical Cyclone Monica 868
Typhoon Andy 871
Typhoon Yuri 869
Typhoon Forrest 872
Hurricane Patricia 875{Will probably be revised to}

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Haiyan would be >885. There was a powerful STR as well as high backgroound pressures

I've seen this line of thinking thrown around quite a bit, and I'd like to challenge it with some actual data.

First, what actually constitutes high background pressures in the Tropical Western Pacific? To understand this, it is first imperative to know what normal background pressures are for the basin. Per Atkinson and Holliday, typical background pressures for the WPac were found to be about 1010 mb. Using the common practice that the environmental pressure of a tropical cyclone is 2 mb more than the pressure of the outermost closed isobar, that would be an average OCI of 1008 mb. As far as I can tell, on November 7th, 2013, Haiyan had an OCI anywhere between 1000 mb (JTWC best track) and 1008 mb (NCEP analysis), with JMA in between with an OCI near or just above 1004 mb (below). I'd probably lean more to the higher side of that range myself, but Haiyan's environmental pressures were average at the highest. For the record, the pressures surrounding Megi '10 were similar per NCEP and even higher per JMA and JTWC than they were for Haiyan!

Image

As far as subtropical ridging is concerned, Haiyan was indeed forced primarily westward at a quick pace by a powerful zonal subtropical ridge with 500 mb heights >588 dam. Per JMA analysis (below), the 500 mb ridge axis north of Haiyan appears to max out around 590 dam in the vicinity of 20ºN with some slightly higher heights off to the east near Wake. A strong ridge for sure, but very deep systems have been observed in the presence of such ridges. In 2010, Megi was forced WSW towards Luzon by a ~589 dam zonal thumb off the main >594 dam subtropical ridge (link).

Image

As far as track, environmental conditions, and intensity is concerned, Super Typhoon Rita from 1978 is quite possibly the best analog for Haiyan that we have. Rita had two peaks, with the first coming on October 23rd, 1978 and the second two days later on October 25th. Zonal subtropical ridging to Rita's north maintained >591 dam 500 mb heights on both the 23rd and 25th. The OCI started out between 1008 and 1012 mb on the 23rd before falling to values more similar to those with Haiyan by the 25th. It should also be noted that Rita was a smaller than average system, particularly during the first peak on the 23rd. Despite this, Rita maintained pressures at or below 900 mb for three and a half days prior to a Luzon landfall, an incredible length of time, and with measured peaks of 882 and 878 mb on the 23rd and 25th, respectively. Using the 700 mb height of 2007 m from the 25th, the Jordan Equation estimates a 876 mb pressure at the same time as the 878 mb pressure measurement. The aforementioned 700 mb height is the fifth lowest on record, and only within 1 m of Nora '73 and 2 m of Ida '58's heights. Rita was clearly an exceptionally intense tropical cyclone. Below, I have the pressure readings and 700 mb extrapolated pressures from Rita's recon missions plotted out.

Image

Does this mean that Haiyan was as deep or perhaps even deeper than Rita? Not necessarily. Each individual storm is unique and has its own characteristics and quirks. However, I think it's silly to handwave Haiyan's pressure and say it's not for sure exceptionally deep. I honestly believe anything between the current official 895 mb estimate and Hoarau's 860 mb estimate could be a pressure that Haiyan was able to achieve at its deepest. I personally favor the middle ground of that range, somewhere between 870-885 mb, but it's unfortunately too difficult to pin down with high confidence.

*Edits to clean up some wording and such.
Last edited by 1900hurricane on Tue Nov 14, 2017 1:53 pm, edited 2 times in total.
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Re: Discussion of Intense Tropical Cyclones

#243 Postby Alyono » Sun Nov 12, 2017 10:17 pm

careful about using extrapolated 700mb pressures. As we've seen in the Atlantic, they can be off by several mb

Also, I have a question for about the Holliday method. From where were his background pressures sampled? It makes a HUGE difference if they were in the monsoon trough or out of it. We see this in the Atlantic as well with these late season (and some early season as well) Caribbean systems (SOME of them, others are tropical waves that experience increased convergence due to trade wind reduction, those have normal p/w relationships)
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Re: Discussion of Intense Tropical Cyclones

#244 Postby 1900hurricane » Sun Nov 12, 2017 10:56 pm

Of course, there is bound to be some error when using a statistical estimate. The primary reason I provided the extrapolations is to fill in a few spots where a pressure reading was absent (from the JTWC report, below). However, it's also worth noting that dropsondes did not record wind data at that time, so it also isn't impossible that actual pressure could be a couple of millibars lower than the measurement if the exact pressure center was missed. Regardless, the pressure readings and extrapolated pressures are all within a couple of millibars of each other near peak intensity.

Image

As for how AH came to their conclusion on WPac background pressure, it appears they used information provided by Takahashi. However, a study by Knaff and Sampson found an average environmental pressure of about 1009 mb for the WPac when using the 1966-1987 period, which is fairly close to Takahashi's 1010 mb used by AH.

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Re: Discussion of Intense Tropical Cyclones

#245 Postby euro6208 » Sat Nov 25, 2017 7:56 am

Image



Haiyan? Megi? Other post 1987 typhoons? :double:
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Re: Intense Tropical Cyclone Discussion

#246 Postby 1900hurricane » Thu Nov 30, 2017 11:41 pm

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

Image


Hurricane Katrina when recon measured 150kt and 902mb

Image

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

I realize this is an old post from the first page, but Katrina '05 and Jamgmi '08 are probably a little more similar in intensity than their best track intensities indicate. Katrina had maximum flight level winds of 166 kt (0.9 reduction factor estimates 149 kt at the surface) recorded at 1422Z on August 28th, 2005, while Jangmi had a similar 163 kt recorded at 700 mb (same reduction yields an estimated 147 kt at the surface) at 0617Z on September 27, 2008. Their measured pressures on their center passes were 907 mb and 906 mb, respectively. I'd still call Jangmi the more impressive of the two visually, but Katrina was at least a little more impressive around the time the highest flight level winds were recorded (below). Katrina's pressure bottomed out at 902 mb around 18Z, but flight level winds continued to decrease with time, perhaps due to a developing outer eyewall (also below). A great paper with data on Jangmi '08 can be found here.

Image

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Re: Discussion of Intense Tropical Cyclones

#247 Postby CrazyC83 » Fri Dec 01, 2017 8:15 pm

From what I can tell, in the Dvorak satellite era, storms that reached cat 4 or 5 without Recon at an Atlantic peak (relative or absolute) were:

* 1981 Harvey
* 1988 Helene
* 1991 Claudette
* 1995 Felix
* 1996 Edouard
* 1999 Cindy
* 1999 Gert
* 2000 Isaac
* 2003 Isabel
* 2004 Karl
* 2008 Ike
* 2010 Igor
* 2010 Julia
* 2011 Katia
* 2011 Ophelia

Isabel is the only storm in this era known to have reached cat 5 without Recon in the Atlantic.
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Re: Discussion of Intense Tropical Cyclones

#248 Postby 1900hurricane » Fri Dec 01, 2017 10:02 pm

CrazyC83 wrote:From what I can tell, in the Dvorak satellite era, storms that reached cat 4 or 5 without Recon at an Atlantic peak (relative or absolute) were:

* 1981 Harvey
* 1988 Helene
* 1991 Claudette
* 1995 Felix
* 1996 Edouard
* 1999 Cindy
* 1999 Gert
* 2000 Isaac
* 2003 Isabel
* 2004 Karl
* 2008 Ike
* 2010 Igor
* 2010 Julia
* 2011 Katia
* 2011 Ophelia

Isabel is the only storm in this era known to have reached cat 5 without Recon in the Atlantic.

Hard to miss the clear-as day DT T7.0 that Isabel '03 produced over the central Atlantic. It's easily the best satellite presentation I've ever seen while east of the Caribbean, Irma included.

Image

Image

For the most part though, the most intense systems happen in the western portion of the basin, where the waters are generally warmer and the tropopause is typically higher. Coincidentally, that's where the best recon coverage is, so it's somewhat more uncommon to have a particularly intense system outside the NAtl recon coverage area. However, I think one more storm that could be added to your list once reanalysis gets there is Hurricane Francis from 1980. This is a system that is operationally rated an entry-level category 3, but based on IR imagery, I think it's possible it could have been a category 4, perhaps even a very strong one while very far east in the basin.

Image

Image

Image

(Edited to correct Francis '80's operational intensity)
Last edited by 1900hurricane on Fri Dec 01, 2017 10:13 pm, edited 1 time in total.
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Re: Discussion of Intense Tropical Cyclones

#249 Postby CrazyC83 » Fri Dec 01, 2017 10:04 pm

Frances 1980 looks incredible for a storm east of 30W. I agree that will probably get a big upgrade - I'd say that is T6.5 and I would go with an intensity of 125 kt there.
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Re: Discussion of Intense Tropical Cyclones

#250 Postby 1900hurricane » Sat Dec 02, 2017 1:31 am

I've just completed a little reanalysis on Super Typhoon Tip from 1979. It's nothing crazy complex, but I figured It could give a better representation than the current best track indicates. My mock b-deck in its current state is pictured below.

Image

Estimated maximum sustained winds rely heavily on the rounded off KZC values, but I did make a few slight up or down tweaks in a few places depending on the situation. I adjusted upwards a little bit on some of the rapid/explosive deepening phases and downwards in places where Tip had weakened after peak intensity and was dealing with eyewall replacement/structural issues. Below, I have plotted the original best track wind values, the raw KZC wind outputs, and two slightly different versions of winds expected from Atkinson-Holliday: one using the default environmental pressure and the other using my analyzed environmental pressures. As you can see, the original best track intensities closely follow the AH values for a significant stretch of Tip's life. Interestingly, it's also worth noting that the KZC and AH expected winds are basically the same for a good chunk of time following peak intensity. This is largely due to massive TS wind radii.

Image

Speaking of TS wind radii, I actually made the average TS wind radii estimates myself based on regression between JMA's listed 30 kt wind radii and JTWC's 34 kt wind radii for the 2016 Typhoon Season. I wanted to include more seasons originally in my regression analysis, but JTWC did not quality control their 34 kt wind radii prior to 2016, and it's entirely absent prior to 2004. In stark contrast, JMA has good 30 kt wind radii data dating back to 1977, conveniently provided by Digital Typhoon (which is also where I gathered my OCI data, as well as viewed satellite images). I used the windcode 'AAA' in my mock b-deck, meaning extending all the way around the circulation. Unlike a normal b-deck however, mine is an average rather than a maximum extent, since that is what I used with KZC. I might go back and try to do semicircle data at some point based on the JMA data. NotoSans is also putting together a hurdat type file for the WPac, so I'll probably do a second estimate based on his wind radii when I get the chance.

Image

Tip had good recon coverage for basically its entire life, which resulted in a good central pressure dataset. I followed it very closely, finding little reason to deviate from the pressures listed in the 1979 JTWC report. Unfortunately, some of the biggest gaps in coverage came during Tip's two most prolific deepening phases. The second one in particular is most troubling since it involves Tip's maximum intensity. At 0353Z October 12th, 1979, recon flew into Tip for the first time in a little over 12 hours and recorded the record low 870 mb central pressure, a pressure 30 mb lower than the previous plane found. However, subsequent passes found that the pressure was rising fairly rapidly, and the pressure ended up rising back above 900 mb about as quickly as it fell. The real question is how much deeper, if any, was the pressure prior to the 870 mb pass? This is one I struggled with for a little while, but I ended up settling on an 868 mb pressure at 03Z October 12. This is after the coldest CDO cloud tops observed between 18-00Z (a time period where I nudged the winds up a little above the KZC values), but also coincides with the warmest eye temperature measured by geostationary satellite imagery, about 22ºC. Even with today's high resolution satellites, that is an extremely high value. Furthermore, the 30ºC 700 mb temperature measured by recon on the 870 mb pass indicated that Tip was likely still near peak intensity. Satellite presentation began to more quickly degrade after 03Z.

Image

My 175 kt peak intensity estimate matches up well with the 173 kt estimated by Veldon's ADT study, which makes me optimistic that my values aren't garbage, especially since we arrived with similar numbers with very different methodologies. I'm looking forward to reanalyzing more systems in a similar fashion, but I'm not quite sure if I should try analyzing some of the other more impressive systems like Rita '78, Forrest '83, and Vanessa '84 or if I should try finishing off the other systems from 1979 like Alice, Hope, Judy, Owen, and Sarah before moving onto other systems. Regardless I'm looking forward to reanalyzing more systems!
Last edited by 1900hurricane on Sat Dec 02, 2017 9:13 am, edited 1 time in total.
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Re: Discussion of Intense Tropical Cyclones

#251 Postby euro6208 » Sat Dec 02, 2017 3:18 am

So a gap in recon between the first and second peak, makes you wonder if other typhoons experience the same thing. Hence missing the lowest pressure and highest winds.
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Re: Discussion of Intense Tropical Cyclones

#252 Postby 1900hurricane » Sat Dec 02, 2017 10:10 am

12 hourly recon fixes are pretty common for tropical cyclones not imminently threatening land even today in the NAtl. Prior to passing Guam, Tip had nearly continuous recon coverage prior to passing by Guam, but that dropped to the 12 hour fixes once Tip was no longer threatening the US territory. Recon was also running missions into Typhoon Sarah in the South China Sea at that time. Obviously, more coverage is better, but 12 hour fixes coupled with satellite imagery is usually good enough to estimate system intensity with a good deal of accuracy, barring the system being monitored doesn't change intensity quickly both up and down. Unfortunately, that's exactly what Tip did, similar to Patricia '15 in that regard.
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Re: Discussion of Intense Tropical Cyclones

#253 Postby Ptarmigan » Thu Dec 07, 2017 11:18 pm

I agree about Hurricane Frances (1980) being more intense. I would not be surprised if it was a Category 4.
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Re: Discussion of Intense Tropical Cyclones

#254 Postby CrazyC83 » Sat Dec 09, 2017 12:44 am

Ptarmigan wrote:I agree about Hurricane Frances (1980) being more intense. I would not be surprised if it was a Category 4.


I'd need to see other images, but I would set it at 125 kt right there. That would EASILY be the strongest storm so far east - I'm not aware of any storms that strong even east of 40W, forget 30W. That should also be a wakeup call for Cape Verde knowing that a cat 4 storm could occur so close to them...

What site has those old satellites? I'm curious about other older storms.
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Re: Discussion of Intense Tropical Cyclones

#255 Postby Shell Mound » Sat Dec 09, 2017 1:02 pm

CrazyC83 wrote:
Ptarmigan wrote:I agree about Hurricane Frances (1980) being more intense. I would not be surprised if it was a Category 4.


I'd need to see other images, but I would set it at 125 kt right there. That would EASILY be the strongest storm so far east - I'm not aware of any storms that strong even east of 40W, forget 30W. That should also be a wakeup call for Cape Verde knowing that a cat 4 storm could occur so close to them...

What site has those old satellites? I'm curious about other older storms.

http://www.atmos.albany.edu/student/ppapin/maps/gridsat/
https://www1.ncdc.noaa.gov/pub/data/satellite/hursat/
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Re: Discussion of Intense Tropical Cyclones

#256 Postby 1900hurricane » Sat Dec 09, 2017 10:05 pm

Shell Mound wrote:
CrazyC83 wrote:
Ptarmigan wrote:I agree about Hurricane Frances (1980) being more intense. I would not be surprised if it was a Category 4.


I'd need to see other images, but I would set it at 125 kt right there. That would EASILY be the strongest storm so far east - I'm not aware of any storms that strong even east of 40W, forget 30W. That should also be a wakeup call for Cape Verde knowing that a cat 4 storm could occur so close to them...

What site has those old satellites? I'm curious about other older storms.

http://www.atmos.albany.edu/student/ppapin/maps/gridsat/
https://www1.ncdc.noaa.gov/pub/data/satellite/hursat/

Yep, that's exactly where I acquired those images.
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