Discussion of Intense Tropical Cyclones

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Re: Discussion of Intense Tropical Cyclones

#641 Postby Yellow Evan » Fri Aug 13, 2021 6:19 am

mrbagyo wrote:
Shell Mound wrote:http://ibtracs.unca.edu/hursat/1979/1979300N04166.VERA.1979.11.04.1200.19.GMS-1.115.hursat-b1.v07.png
http://ibtracs.unca.edu/hursat/2013/2013306N07162.HAIYAN.2013.11.07.1800.20.MTS-1.142.hursat-b1.v07.png

Based on this comparison, Vera of 1979 (top) looks to be even more intense than Haiyan of 2013 (bottom). Vera’s CDO is smaller yet colder, its outflow is more symmetric, and its eye is smaller and likely similarly warm, given satellite-based limitations. If Haiyan was on the order of 170–175 kt, Vera was likely on the order of 175–180 kt. If I recall correctly, quite a few sub-major and low-end major cyclones from the South Pacific and Indian basins were, based on satellite, likely solid and even “high-end” Category-5 cyclones. Dr. Maue once posted an excellent thread on Twitter in regard to “missed” Category 5s, but unfortunately it has been removed.



Highest flight level wind recorded by recon in Typhoon Vera was 170 knots.


Flight level observations from that era seemed to have sampling issues.
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Re: Discussion of Intense Tropical Cyclones

#642 Postby mrbagyo » Fri Aug 13, 2021 8:54 am

Yellow Evan wrote:Flight level observations from that era seemed to have sampling issues.


The era with suspicious FL obs were the 50s to 60s.
Vera came during the later part of the 70s (Vera is actually preceded by the almighty STY Tip)
Also don't forget that Vera likely possessed a very tight pressure gradient since it was racing at a forward speed between 37 to 41 kph due to an intense ridging to its north.
I'm actually quite satisfied with 1900hurricane's reanalysis with Vera
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Re: Discussion of Intense Tropical Cyclones

#643 Postby 1900hurricane » Fri Aug 13, 2021 5:41 pm

ncforecaster89 wrote:
TROPICALCYCLONEALERT wrote:
ncforecaster89 wrote:
I agree, as others have already stated, that Matthew should be downgraded based on the apparent high bias of the SFMR data in surface winds > 120 kt. Might be an unpopular opinion, but I’ve always felt Dorian was overestimated with the 160 kt estimate; which is way too high a figure considering the 700 mb FLWs of 161 kt (corresponds to only 145 kt). The SFMR is the only data that supported such an extreme estimate and I feel 150 kt is likely a more accurate representation of its MSW at its peak.

Although Dorian currently sits above Irma, the exclusion of the SFMR data would likely put them at the same intensity of 150 kt. Personally, I find Irma to be the more impressive hurricane of the two and actually had a higher 700 mb FLW of 164 kt. Even though I still think of Dorian as an incredibly powerful Cat 5, it should not be tied with the GLDH of 1935...based on the available data.


For what it’s worth, a casual analysis of dropwindsondes in Hurricane Dorian (made possibly only because of the plethora of RMW drops we had from two planes flying into it at peak intensity) implies a flight level wind reduction above the 90% “rule” established by Franklin et al. 2003, albeit still within their accepted range. Anecdotally, storms with higher winds also have a tendency to possess surface winds that are abnormally high relative to the winds found at 700mb, though possible reasons are still unclear and could range from the vertical orientation of the eyewall, the depth of convection, nearness to MPI, and size of the eye. It’s also probable that an extremely healthy system would exceed the statistical average of ~90%, as it would not have to contend with dry air/wind shear interrupting the process that mixes the winds down to the surface. While I’m fairly skeptical of the maximum 177 knot SFMRs in Dorian, I do believe the NHC’s estimate is fairly decent, especially when given the typical 5-10 kt error bound.


Hi TCA,

So sorry I’m just now reading this post and providing a response.

I don’t disagree with your own synopsis, but want to clarify why I feel rather strongly that the current 160 kt estimate is much too high, and Dorian shouldn’t be tied with the GLDH of 1935. To do so, please allow me to post the NHC’s reasoning for their estimate from the TCR:

“Dorian’s estimated peak intensity of 160 kt at 1640 UTC 1 September, which is also the landfall intensity at Elbow Cay in the Abacos, is based on a blend of flight-level winds, dropwindsonde WL150 winds (average wind speed over the lowest 150 m), and multiple SFMR surface wind speed measurements made by both the Air Force Reserve and NOAA Hurricane Hunters during that time period. This estimate integrates the highest SFMR wind value of 178 kt, a 700-mb flight-level peak wind measurement of 161 kt (which is equivalent to an intensity of 145 kt), and a 1325 UTC WL150 wind speed of 177 kt (which is equivalent to a 10-m wind speed of 147 kt) (Fig. 2). It is important to note that the relationship between the SFMR wind values and the flight-level winds was quite consistent for wind speeds of 120 kt or less in Dorian, but not so for equivalent surface wind speeds exceeding 120 kt. As has been noted for other recent intense hurricanes, the discrepancy between surface winds estimated from historical relationships with the peak flight-level winds and SFMR-derived surface winds leads to greater-than-normal uncertainty in Dorian’s peak intensity estimate. The estimated peak intensity may be revised if SFMR data at high winds are recalibrated.”

As I noted previously, the aforementioned likely inflated SFMR measurements are the only data supportive of an intensity greater than 150 kt. That’s the figure that would be ascertained by blending the peak 700 mb FLW, WL150 winds, satellite intensity estimates, and the wind/pressure relationship. Due to the inherent uncertainty and relative subjective nature involved in determining such intensity estimates, I’m more inclined to err on the high-end side if there’s sufficient in-situ data to support it. In this particular case, I feel 150 kt seems like the most logical and applicable figure for Dorian’s peak MSW.

All that said, I suspect the NHC will ultimately modify the peak intensity down to 155 kt once the SFMR has been recalibrated to account for the apparent inflated values at such extreme wind speeds.

Ignoring SFMR completely, I've been privileged to see a draft of the same dropsonde analysis that TCA is referencing here. Using the same methodology as Franklin, Black, & Valde, the study that established both the standard flight level wind reductions and dropsonde reductions used today, the flight level winds might actually have been about 1:1 with the surface winds for Dorian near peak intensity. Given the number of dropsondes released into Dorian near peak intensity from multiple missions, the consistent signal across all the sonde data appears noteworthy to me. I'm not going to share the entirety of the work here as the analysis remains unpublished, but I will share one figure from the draft: Dorian's mean sounding profile.

Image

Compare to the more standard profile from Franklin, Black, & Valde:

Image

For whatever reason, the winds were just much stronger in the sondes below the 750 m level than the standard profile when referenced against the flight level winds. As I mentioned earlier, this is completely ignoring the SFMR data, which was way out in a near 180 kt la-la land. However, once the new algorithm calibration that appears to be incoming is complete and retroactively applied to past data, I'll be very curious to see how closely it falls to both peak flight level winds and the NHC's current intensity estimate: ~160 kt.
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Re: Discussion of Intense Tropical Cyclones

#644 Postby ncforecaster89 » Fri Aug 13, 2021 8:12 pm

1900hurricane wrote:
ncforecaster89 wrote:
TROPICALCYCLONEALERT wrote:
For what it’s worth, a casual analysis of dropwindsondes in Hurricane Dorian (made possibly only because of the plethora of RMW drops we had from two planes flying into it at peak intensity) implies a flight level wind reduction above the 90% “rule” established by Franklin et al. 2003, albeit still within their accepted range. Anecdotally, storms with higher winds also have a tendency to possess surface winds that are abnormally high relative to the winds found at 700mb, though possible reasons are still unclear and could range from the vertical orientation of the eyewall, the depth of convection, nearness to MPI, and size of the eye. It’s also probable that an extremely healthy system would exceed the statistical average of ~90%, as it would not have to contend with dry air/wind shear interrupting the process that mixes the winds down to the surface. While I’m fairly skeptical of the maximum 177 knot SFMRs in Dorian, I do believe the NHC’s estimate is fairly decent, especially when given the typical 5-10 kt error bound.


Hi TCA,

So sorry I’m just now reading this post and providing a response.

I don’t disagree with your own synopsis, but want to clarify why I feel rather strongly that the current 160 kt estimate is much too high, and Dorian shouldn’t be tied with the GLDH of 1935. To do so, please allow me to post the NHC’s reasoning for their estimate from the TCR:

“Dorian’s estimated peak intensity of 160 kt at 1640 UTC 1 September, which is also the landfall intensity at Elbow Cay in the Abacos, is based on a blend of flight-level winds, dropwindsonde WL150 winds (average wind speed over the lowest 150 m), and multiple SFMR surface wind speed measurements made by both the Air Force Reserve and NOAA Hurricane Hunters during that time period. This estimate integrates the highest SFMR wind value of 178 kt, a 700-mb flight-level peak wind measurement of 161 kt (which is equivalent to an intensity of 145 kt), and a 1325 UTC WL150 wind speed of 177 kt (which is equivalent to a 10-m wind speed of 147 kt) (Fig. 2). It is important to note that the relationship between the SFMR wind values and the flight-level winds was quite consistent for wind speeds of 120 kt or less in Dorian, but not so for equivalent surface wind speeds exceeding 120 kt. As has been noted for other recent intense hurricanes, the discrepancy between surface winds estimated from historical relationships with the peak flight-level winds and SFMR-derived surface winds leads to greater-than-normal uncertainty in Dorian’s peak intensity estimate. The estimated peak intensity may be revised if SFMR data at high winds are recalibrated.”

As I noted previously, the aforementioned likely inflated SFMR measurements are the only data supportive of an intensity greater than 150 kt. That’s the figure that would be ascertained by blending the peak 700 mb FLW, WL150 winds, satellite intensity estimates, and the wind/pressure relationship. Due to the inherent uncertainty and relative subjective nature involved in determining such intensity estimates, I’m more inclined to err on the high-end side if there’s sufficient in-situ data to support it. In this particular case, I feel 150 kt seems like the most logical and applicable figure for Dorian’s peak MSW.

All that said, I suspect the NHC will ultimately modify the peak intensity down to 155 kt once the SFMR has been recalibrated to account for the apparent inflated values at such extreme wind speeds.

Ignoring SFMR completely, I've been privileged to see a draft of the same dropsonde analysis that TCA is referencing here. Using the same methodology as Franklin, Black, & Valde, the study that established both the standard flight level wind reductions and dropsonde reductions used today, the flight level winds might actually have been about 1:1 with the surface winds for Dorian near peak intensity. Given the number of dropsondes released into Dorian near peak intensity from multiple missions, the consistent signal across all the sonde data appears noteworthy to me. I'm not going to share the entirety of the work here as the analysis remains unpublished, but I will share one figure from the draft: Dorian's mean sounding profile.

https://i.imgur.com/KhILFL3.png

Compare to the more standard profile from Franklin, Black, & Valde:

https://journals.ametsoc.org/view/journals/wefo/18/1/images/i1520-0434-18-1-32-f08.gif

For whatever reason, the winds were just much stronger in the sondes below the 750 m level than the standard profile when referenced against the flight level winds. As I mentioned earlier, this is completely ignoring the SFMR data, which was way out in a near 180 kt la-la land. However, once the new algorithm calibration that appears to be incoming is complete and retroactively applied to past data, I'll be very curious to see how closely it falls to both peak flight level winds and the NHC's current intensity estimate: ~160 kt.


Thanks so much for sharing that fascinating data. Even so, the W150 (average of lowest 150 m) winds were only equivalent to a 145 kt intensity as were the 700 mb FLWs. Consequently, it seems highly unlikely that Dorian had surface winds greater than 155 kt and more likely closer to 150 kt. As you noted, it will be most interesting to see how the new SFMR calibration affects the current official intensity estimate of 160 kt.
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Re: Discussion of Intense Tropical Cyclones

#645 Postby Ptarmigan » Sun Aug 15, 2021 8:53 pm

CrazyC83 wrote:
ncforecaster89 wrote:
aspen wrote:No way in hell Matthew was a Cat 5 if Iota was a Cat 4 despite a 140 kt valid SFMR measurement and Dvorak support for 140 kt.

Once again, I have to wonder about Dorian’s SFMR. Unlike Iota, Dorian had extremely high FL winds in all four quadrants (~160 kt in at least one quadrant), and dropsondes recorded that rare V signature showing that air was sinking all the way down to the surface, indicating winds would be translating from FL to the surface rather well. All quadrants also had 160 kt or greater valid SFMR measurements, and some even got up to 170 kt. Maybe the low ocean depth was messing with SFMR, but with effective translation of ~160 kt FL winds to the surface, it’s hard to believe they’re that erroneous.


I agree, as others have already stated, that Matthew should be downgraded based on the apparent high bias of the SFMR data in surface winds > 120 kt. Might be an unpopular opinion, but I’ve always felt Dorian was overestimated with the 160 kt estimate; which is way too high a figure considering the 700 mb FLWs of 161 kt (corresponds to only 145 kt). The SFMR is the only data that supported such an extreme estimate and I feel 150 kt is likely a more accurate representation of its MSW at its peak.

Although Dorian currently sits above Irma, the exclusion of the SFMR data would likely put them at the same intensity of 150 kt. Personally, I find Irma to be the more impressive hurricane of the two and actually had a higher 700 mb FLW of 164 kt. Even though I still think of Dorian as an incredibly powerful Cat 5, it should not be tied with the GLDH of 1935...based on the available data.


Irma also had a surface observation of note: an official gust of (I believe) 173 kt in St. Martin. That lends itself well to an intensity of 155 kt, which I believe is reasonable. Dorian is a case with an even greater discrepancy. 150 or 155 kt would likely make more sense, but at that time 160 kt seemed best with the investigation underway. Dorian's floor is probably 150 kt.

For all the recent strong 4s and 5s (i.e. 130 kt or greater):

Matthew - FLW 134/121 at surface, SFMR 143, Dvorak 127, P-W 118. BT is 145 kt but my estimate is 130 kt at that time.
Irma - FLW 164/148 (and 170 at non-standard/about 150), SFMR 160, Dvorak 140, P-W 152, surface G173. BT is 155 kt and reasonable.
Jose - FLW 144/130, SFMR 142, Dvorak 115, P-W 125, no surface data. BT is 135 kt and probably reasonable (the thoughts of it being cat 5 are likely gone now).
Maria - FLW 157/141, SFMR 152, Dvorak 140, P-W 154. BT is 150 kt and probably reasonable.
Michael - FLW 152/137, SFMR 138 (and suspect), Dvorak 140, P-W 141, radar 147. BT is 140 kt, although a case for 145 kt could be made.
Dorian - FLW 161/145, SFMR 178, Dvorak 127, P-W 154. BT is 160 kt with a high degree of uncertainty; floor is 150 kt with 155 kt also reasonable.
Lorenzo - Dvorak 140 but no other data. BT is 140 kt and hard to argue.
Laura - FLW 148/133, SFMR 138 (and suspect), Dvorak 127, P-W 124, radar ~135. Operational BT is 130 kt, awaiting TCR. My best estimate is 135 kt.
Eta - FLW 137/123 (very limited data), SFMR 135, Dvorak 140, P-W 137. Operational BT is 130 kt, awaiting TCR.
Iota - FLW 143/129, SFMR 140, Dvorak 140, P-W 145. BT is 135 kt, which is the current source of controversy but the flight-level winds don't support higher.


I always thought Matthew being Category 5 was suspect. As for Iota, I think it was a Category 5 hurricane. The strongest in Iota was likely in a very small area that may have not been measured.
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Re: Discussion of Intense Tropical Cyclones

#646 Postby kevin » Mon Aug 23, 2021 7:52 am

I just read that a study found a new record for the coldest ever recorded cloudtops. The data is from 13:38 UTC on December 29, 2018. The cloudtop had a temperature of 161.96K (-111C, -168F). Interestingly, the record is not associated with an intense storm, but instead what they describe as a 'tropical deep convective event'. While it isn't mentioned in the link I did some additional searching and it seems the measurement is related to Tropical Depression 03F or at least an associated cloud band to the north of it. Goes to show that even a 'weak' tropical system can have extremely cold clouds. The 2nd coldest cloudtop temperature is by typhoon Kammuri (a cat 4) in 2019, which has cloudtop temperatures of 163.75 K (-109C, -165F). More information here: https://www.geographyrealm.com/coldest-temperature-of-clouds-recorded-by-a-satellite/. Does anyone know any other measurements that come close to these values?

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Re: Discussion of Intense Tropical Cyclones

#647 Postby Ubuntwo » Tue Aug 24, 2021 4:45 pm

CrazyC83 wrote:Michael - FLW 152/137, SFMR 138 (and suspect), Dvorak 140, P-W 141, radar 147. BT is 140 kt, although a case for 145 kt could be made.


Since I'm not sure anyone has mentioned this here: operationally a set of SFMR readings from Michael's RFQ were not transmitted. However, reconstruction of raw data found maximum values of 152kt, in 89ft deep water so likely not contaminated by shoaling. Even with the SFMR bias a pretty strong case could be made for 145kt. We'll have to see what comes of the SFMR recalibration efforts.
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Re: Discussion of Intense Tropical Cyclones

#648 Postby Ubuntwo » Tue Aug 31, 2021 3:53 am

Ida is a good example of an aborted ERC due to land interaction in intense TCs.

A concentric eyewall formed before landfall w/ a well defined moat. The inner eyewall underwent small trochoidal wobbles up until a little after landfall.
Image

~21z - Ida's inner eyewall redevelops mesovortices and the moat starts to fill in.
Image

21:40z - Convection refocuses on the NE quad as the moat continues filling in.
Image

~23z - The eyewalls begin merging.
Image

~24z - While the eye remains distinct, the eyewalls have merged into a uniform intense convective band.
Image

Long loop [large]:
Image
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Re: Discussion of Intense Tropical Cyclones

#649 Postby aspen » Tue Sep 28, 2021 9:34 am

The results of the limited recon into Hurricane Sam around its peak suggest that storms like Felicia and Douglas were under-estimated by 5-15 kt. While no recon was there to measure Sam's exact peak (I still would like to know why that flight was shifted), the first pass about an hour into Sam's first EWRC yielded 929mb, and the second pass saw a 3-5 mb/hr filling rate. Therefore, the pressure had likely levelled off in the mid-920s from 10-20z Sunday, supporting 135-140 kt using the KCZ wind-pressure relationship. At the time of peak intensity, Sam had a nearly perfect W ring, with the exception of a few B pixels at various points throughout the day before the EWRC, and eye temps of up to 19C (WMG pixels).
Image

Felicia also had a W ring at peak intensity, but despite a WMG eye like Sam and some CMG pixels, ADT had a slightly difficult time with it. The thickness of the W ring also messed with Dvorak estimates. The NHC put Felicia's peak at a reasonable 125kt/945mb in its TCR, but seeing how Sam was running 5-10kt above ADT estimates and 10mb deeper than official pressure estimates during its peak, it's possible Felicia was indeed underestimated. Felicia's core was broader than Sam's so I doubt it was as strong, but 130kt with a pressure in the high 930s/low 940s seems reasonable; Hector '18 was 135kt/938mb in a similar region while having a similar structure.
Image

Douglas never attained a perfect W ring, but had a core size similar to Sam's and had an impressive Stadium Effect, WMG eye. It was put at 115kt, which seemed too low then and definitely seems too low now. I also don't think it was near Sam, but 125kt is reasonable.

Thoughts?
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Re: Discussion of Intense Tropical Cyclones

#650 Postby MarioProtVI » Tue Sep 28, 2021 3:50 pm

aspen wrote:The results of the limited recon into Hurricane Sam around its peak suggest that storms like Felicia and Douglas were under-estimated by 5-15 kt. While no recon was there to measure Sam's exact peak (I still would like to know why that flight was shifted), the first pass about an hour into Sam's first EWRC yielded 929mb, and the second pass saw a 3-5 mb/hr filling rate. Therefore, the pressure had likely levelled off in the mid-920s from 10-20z Sunday, supporting 135-140 kt using the KCZ wind-pressure relationship. At the time of peak intensity, Sam had a nearly perfect W ring, with the exception of a few B pixels at various points throughout the day before the EWRC, and eye temps of up to 19C (WMG pixels).
https://i.imgur.com/evRCBdf.jpg

Felicia also had a W ring at peak intensity, but despite a WMG eye like Sam and some CMG pixels, ADT had a slightly difficult time with it. The thickness of the W ring also messed with Dvorak estimates. The NHC put Felicia's peak at a reasonable 125kt/945mb in its TCR, but seeing how Sam was running 5-10kt above ADT estimates and 10mb deeper than official pressure estimates during its peak, it's possible Felicia was indeed underestimated. Felicia's core was broader than Sam's so I doubt it was as strong, but 130kt with a pressure in the high 930s/low 940s seems reasonable; Hector '18 was 135kt/938mb in a similar region while having a similar structure.
https://i.imgur.com/i3WdwEE.jpg

Douglas never attained a perfect W ring, but had a core size similar to Sam's and had an impressive Stadium Effect, WMG eye. It was put at 115kt, which seemed too low then and definitely seems too low now. I also don't think it was near Sam, but 125kt is reasonable.

Thoughts?

NHC is very likely (>95% chance) not gonna up Sam to C5, given Jose had similar possibilities but was not upped in TCR. It will most likely be 135 kt. If it weren’t for Jose I would’ve leaned more towards C5 but given how Jose was treated I am very skeptical if it was one.
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Re: Discussion of Intense Tropical Cyclones

#651 Postby Teban54 » Tue Sep 28, 2021 3:54 pm

MarioProtVI wrote:
aspen wrote:The results of the limited recon into Hurricane Sam around its peak suggest that storms like Felicia and Douglas were under-estimated by 5-15 kt. While no recon was there to measure Sam's exact peak (I still would like to know why that flight was shifted), the first pass about an hour into Sam's first EWRC yielded 929mb, and the second pass saw a 3-5 mb/hr filling rate. Therefore, the pressure had likely levelled off in the mid-920s from 10-20z Sunday, supporting 135-140 kt using the KCZ wind-pressure relationship. At the time of peak intensity, Sam had a nearly perfect W ring, with the exception of a few B pixels at various points throughout the day before the EWRC, and eye temps of up to 19C (WMG pixels).
https://i.imgur.com/evRCBdf.jpg

Felicia also had a W ring at peak intensity, but despite a WMG eye like Sam and some CMG pixels, ADT had a slightly difficult time with it. The thickness of the W ring also messed with Dvorak estimates. The NHC put Felicia's peak at a reasonable 125kt/945mb in its TCR, but seeing how Sam was running 5-10kt above ADT estimates and 10mb deeper than official pressure estimates during its peak, it's possible Felicia was indeed underestimated. Felicia's core was broader than Sam's so I doubt it was as strong, but 130kt with a pressure in the high 930s/low 940s seems reasonable; Hector '18 was 135kt/938mb in a similar region while having a similar structure.
https://i.imgur.com/i3WdwEE.jpg

Douglas never attained a perfect W ring, but had a core size similar to Sam's and had an impressive Stadium Effect, WMG eye. It was put at 115kt, which seemed too low then and definitely seems too low now. I also don't think it was near Sam, but 125kt is reasonable.

Thoughts?

NHC is very likely (>95% chance) not gonna up Sam to C5, given Jose had similar possibilities but was not upped in TCR. It will most likely be 135 kt. If it weren’t for Jose I would’ve leaned more towards C5 but given how Jose was treated I am very skeptical if it was one.

Wasn't Jose's case mostly because they were skeptical with SFMR? I remember that was explicitly mentioned in the TCR.

That would not really be an issue for Sam as it didn't even have these frequent SFMR readings in the first place.
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Re: Discussion of Intense Tropical Cyclones

#652 Postby Ubuntwo » Tue Sep 28, 2021 4:08 pm

MarioProtVI wrote:NHC is very likely (>95% chance) not gonna up Sam to C5, given Jose had similar possibilities but was not upped in TCR. It will most likely be 135 kt. If it weren’t for Jose I would’ve leaned more towards C5 but given how Jose was treated I am very skeptical if it was one.

I think NHC will keep Sam at 135kt, but Sam still makes a stronger 5 than Jose. Jose's pressure bottomed out in the upper 930s while Sam was a smaller storm in the upper 920s. While recon missed the peak of both storms, there was a much more marked deterioration with Sam before recon arrived. Sam also had a drier, warmer eye (Sam peaked over 20C and maintained that temperature for several hours). I would not be surprised to see Jose bumped down to 130kt once the SFMR study is wrapped up.
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Re: Discussion of Intense Tropical Cyclones

#653 Postby MarioProtVI » Tue Sep 28, 2021 5:24 pm

Ubuntwo wrote:
MarioProtVI wrote:NHC is very likely (>95% chance) not gonna up Sam to C5, given Jose had similar possibilities but was not upped in TCR. It will most likely be 135 kt. If it weren’t for Jose I would’ve leaned more towards C5 but given how Jose was treated I am very skeptical if it was one.

I think NHC will keep Sam at 135kt, but Sam still makes a stronger 5 than Jose. Jose's pressure bottomed out in the upper 930s while Sam was a smaller storm in the upper 920s. While recon missed the peak of both storms, there was a much more marked deterioration with Sam before recon arrived. Sam also had a drier, warmer eye (Sam peaked over 20C and maintained that temperature for several hours). I would not be surprised to see Jose bumped down to 130kt once the SFMR study is wrapped up.

Jose’s SFMRs were recorded after the satellite presentation had begun degrading, so 135 kt for it still stands
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Re: Discussion of Intense Tropical Cyclones

#654 Postby Ubuntwo » Tue Sep 28, 2021 5:37 pm

MarioProtVI wrote:Jose’s SFMRs were recorded after the satellite presentation had begun degrading, so 135 kt for it still stands

SFMR maxed out at 142kt in Jose (raw T 1.0 below peak, 125kt was recorded .5 below peak) and 144kt in Sam (raw T .7 below peak, 134kt was recorded .9 below peak). They are all in the suspect range of 130kt+ so will be reassessed once the ongoing study is complete.
Last edited by Ubuntwo on Tue Sep 28, 2021 5:43 pm, edited 1 time in total.
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aspen
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Re: Discussion of Intense Tropical Cyclones

#655 Postby aspen » Tue Sep 28, 2021 5:42 pm

Ubuntwo wrote:
MarioProtVI wrote:Jose’s SFMRs were recorded after the satellite presentation had begun degrading, so 135 kt for it still stands

SFMR maxed out at 142kt in Jose (raw T 1.0 below peak, 125kt was recorded .5 below peak) and 144kt in Sam (raw T .7 below peak, 134kt was recorded .9 below peak). They are all in the suspect range of 130kt+ so will be reassessed once the ongoing study is complete.

Also, that 144kt SFMR from Sam was recorded two hours into Sam’s degrading satellite appearance as that botched EWRC began. If recon was there in the 12z-18z time frame, when Sam’s satellite presentation peaked and could be argued as a T#7.0 system, it probably would’ve found 150+ kt SFMR; however, they might’ve been inflated and instead support 140-145 kt, although the CIMSS MPI chart showed Sam could’ve maxed out at 150 kt.
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Re: Discussion of Intense Tropical Cyclones

#656 Postby Ubuntwo » Tue Sep 28, 2021 6:01 pm

aspen wrote:Also, that 144kt SFMR from Sam was recorded two hours into Sam’s degrading satellite appearance as that botched EWRC began. If recon was there in the 12z-18z time frame, when Sam’s satellite presentation peaked and could be argued as a T#7.0 system, it probably would’ve found 150+ kt SFMR; however, they might’ve been inflated and instead support 140-145 kt, although the CIMSS MPI chart showed Sam could’ve maxed out at 150 kt.

144kt was recorded shortly after the eye cleared out and 134kt was a few hours after weakening began.

KZC analysis for various MSLP:

Between the two flights avg. gale radius expanded from 65 nautical miles to 73, so 70 nm is an approximation for peak.

Translational speed can be averaged to 7 kt.

Latitude of peak is estimated at 14N.

*Outermost closed isobar I am pinning at 1011 mb based on model analyses.

929 mb: 139.4kt
927 mb: 141.5kt
925 mb: 143.6kt
923 mb: 145.7kt
Last edited by Ubuntwo on Tue Sep 28, 2021 8:09 pm, edited 1 time in total.
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Kendall -> SLO -> PBC

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Re: Discussion of Intense Tropical Cyclones

#657 Postby aspen » Tue Sep 28, 2021 6:37 pm

Ubuntwo wrote:
aspen wrote:Also, that 144kt SFMR from Sam was recorded two hours into Sam’s degrading satellite appearance as that botched EWRC began. If recon was there in the 12z-18z time frame, when Sam’s satellite presentation peaked and could be argued as a T#7.0 system, it probably would’ve found 150+ kt SFMR; however, they might’ve been inflated and instead support 140-145 kt, although the CIMSS MPI chart showed Sam could’ve maxed out at 150 kt.

144kt was recorded shortly after the eye cleared out and 134kt was a few hours after weakening began.

KZC analysis for various MSLP:

Between the two flights avg. gale radius expanded from 65 nautical miles to 73, so 70 nm is an approximation for peak.

Translational speed can be averaged to 7 kt.

Latitude of peak is estimated at 14N.

Radius of outermost closed isobar I am pinning at 1011 mb based on model analyses.

929 mb: 139.4kt
927 mb: 141.5kt
925 mb: 143.6kt
923 mb: 145.7kt

Yeah you’re right, 144kt was on Saturday night with 130 kt FL winds. SFMR was definitely inflated a bit, but it does seem that Sam was 130-135 kt at that point.

Sam’s CDO started showing the impact of the starting EWRC by 20z-21z Sunday afternoon, and the 929mb drop was at ~22:35z when eye temps had cooled down to the negatives. Assuming that Sam leveled off 3-5mb deeper than when recon found it, that would support a 140 kt Cat 5 according to your KCZ analysis. Maybe it got deeper, but just to be safe I think a filling-in of 3mb between 18z and 22z is reasonable.
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Re: Discussion of Intense Tropical Cyclones

#658 Postby Teban54 » Tue Sep 28, 2021 6:45 pm

aspen wrote:
Ubuntwo wrote:
aspen wrote:Also, that 144kt SFMR from Sam was recorded two hours into Sam’s degrading satellite appearance as that botched EWRC began. If recon was there in the 12z-18z time frame, when Sam’s satellite presentation peaked and could be argued as a T#7.0 system, it probably would’ve found 150+ kt SFMR; however, they might’ve been inflated and instead support 140-145 kt, although the CIMSS MPI chart showed Sam could’ve maxed out at 150 kt.

144kt was recorded shortly after the eye cleared out and 134kt was a few hours after weakening began.

KZC analysis for various MSLP:

Between the two flights avg. gale radius expanded from 65 nautical miles to 73, so 70 nm is an approximation for peak.

Translational speed can be averaged to 7 kt.

Latitude of peak is estimated at 14N.

Radius of outermost closed isobar I am pinning at 1011 mb based on model analyses.

929 mb: 139.4kt
927 mb: 141.5kt
925 mb: 143.6kt
923 mb: 145.7kt

Yeah you’re right, 144kt was on Saturday night with 130 kt FL winds. SFMR was definitely inflated a bit, but it does seem that Sam was 130-135 kt at that point.

Sam’s CDO started showing the impact of the starting EWRC by 20z-21z Sunday afternoon, and the 929mb drop was at ~22:35z when eye temps had cooled down to the negatives. Assuming that Sam leveled off 3-5mb deeper than when recon found it, that would support a 140 kt Cat 5 according to your KCZ analysis. Maybe it got deeper, but just to be safe I think a filling-in of 3mb between 18z and 22z is reasonable.

At this point I think the key to whether Sam gets upgraded to a Cat 5 will be whether NHC extrapolates its peak pressure to below 929 mb. If they do, the minimum pressure would be more likely to be accompanied by Cat 5 winds. If the pressure remains at 929, one can still argue Sam might have been a Cat 5 given the KZC and that Dvorak was consistently too low, but an upgrade becomes much less likely.

As I mentioned somewhere in the Sam thread, pressure extrapolation was done for Patricia, but not for Eta. The Eta TCR did mention the possibility of deepening after recon left, but they only lowered the pressure by 1 mb from operational estimates.
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Re: Discussion of Intense Tropical Cyclones

#659 Postby ncforecaster89 » Tue Sep 28, 2021 6:49 pm

It’s difficult for any of us to make a best educated guess/estimate on intensity utilizing any SFMR data exceeding 120 kt. Consequently, until more research is done and it’s properly recalibrated…it’s probably best to exclude it in making such determinations.
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Re: Discussion of Intense Tropical Cyclones

#660 Postby ncforecaster89 » Tue Sep 28, 2021 6:57 pm

For the reasons others have already mentioned, I’d suggest it’s far more likely than not, based on the totality of the data available…Sam did achieve 140 kt Cat 5 intensity at its peak. In such cases, I prefer to err on the high side given the prospect of under sampling.
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