Discussion of Intense Tropical Cyclones

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Re: Discussion of Intense Tropical Cyclones

#661 Postby aspen » Tue Sep 28, 2021 8:00 pm

Teban54 wrote:
aspen wrote:
Ubuntwo wrote: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.

They should've dropped Eta's pressure by up to 5mb in the TCR (recon found a 5 mb/hr deepening rate an hour or so before the EWRC began to really take over), but this isn't an easy extrapolation to make, because we don't know exactly how much longer Eta was intensifying for and how its deepening rate slowed. It started off at 5mb/hr but definitely slowed as the EWRC neared, but how quickly did that happen? We just don't know. By contrast, Patricia and Sam have two recon fixes in which their peaks fell between, allowing for limits to be put on their peaks based on recon data and structural evolution on satellite.

Recon fixed Sam at 929mb for its first pass on Sunday night, then 932mb, and finally 943mb, all about an hour apart from each other. The filling rate doubled over the course of the flight, so extrapolating that gives a pressure of 926-927mb about an hour before recon arrived. Perhaps it could've been 1-2mb lower than that at Sam's peak. However, based on its steady satellite presentation from 10z-18z and the MPI of the region (around 925mb), it can then be inferred that Sam levelled off in the 925-927mb range for most of the day before starting an exponential weakening trend at 19-20z. A blend of the two KCZ estimates for 925mb and 927mb is either 140 kt or 145 kt, but as I said before, 140 kt is the safe bet.

Also, back to Jose comparisons: Sam had a much longer lasting and more consistent W-ring than Jose ever did. On CIRA's storm archive, I can only find a single frame of a complete W ring for Jose around the time of its 135kt/938mb peak; all other frames have a slightly broken W-ring, like Douglas '20.
Image

Sam, on the other hand, had a true W ring with no B pixels for several hours, up until about 16:30z. For about 2-2.5 hours afterwards, before the rapid collapse of the eye, Sam had a mostly complete ring, although it wasn't good enough to qualify as T#7.0.
Image

The better and more consistent satellite presentation supports Sam being the stronger storm, not just by pressure but also likely by winds. Also, I double-checked Jose's TCR, and it is quite apparent that it was kept at 135kt due to concerns about SFMR. Recon found max FL winds of 135kt and max SFMR of 142kt at ~00:30z 9/9/17, when Jose had significantly degraded from the time of the image further up. I could definitely see it peaking a few mbar deeper and maybe even as a 140kt Cat 5, although it probably would've been briefer than Sam's peak.
Image
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Re: Discussion of Intense Tropical Cyclones

#662 Postby Yellow Evan » Sun Nov 21, 2021 4:48 am

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Re: Discussion of Intense Tropical Cyclones

#663 Postby Teban54 » Sun Nov 21, 2021 10:48 am


Have to say the bias is even greater than I thought, and more than enough to justify the Iota downgrade.
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Re: Discussion of Intense Tropical Cyclones

#664 Postby zzh » Sun Nov 21, 2021 10:53 am

Hurricane Sam 9.26 1624Z
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Eye temp 24.82
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Re: Discussion of Intense Tropical Cyclones

#665 Postby zzh » Sun Nov 21, 2021 11:25 am

Recon on 9.25: FL139kt at 2257Z, SFMR 144kt at 2359Z and 942mb at 2357Z. Note that Sam's satellite presentation had peaked at about 19Z. Recon arrived at about 22Z.
34 KT....... 70NE 90SE 40SW 60NW.
21Z RMW from NHC's advisory.
Recon on 9.26: FL130kt at 2349Z, SFMR 134kt at 2236Z and 929mb at 2237Z. Sam had peaked at about 1645Z and was rapidly deteriorating at this moment. Recon arrived at 2230Z. 21Z RMW:
34 KT....... 80NE 80SE 60SW 70NW.

Don't confuse Sam's first peak with its second peak.
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Re: Discussion of Intense Tropical Cyclones

#666 Postby aspen » Sun Nov 21, 2021 2:11 pm


Michael should be okay, because its Cat 5 upgrade was justified by standard FL-to-surface wind conversions and radar velocities alongside SFMR. The storms at risk are those whose intensities were based mainly on SFMR.

-Matthew: The time has come

-Jose: They should stick with 135 kt to account for the gap in recon, although I doubt it got as strong as Sam.

-Irma: Potentially could see another knock down to 150 kt, which is better supported by standard FL conversions

-Maria: 150 kt seems okay but could be on thin ice. Its 145 kt landfall intensity in Dominica is supported by a verified 130 kt 10-minute sustained reading recorded on the island.

-Michael: As I said, radar and FL measurements still support 140 kt, maybe even 145 kt.

-Dorian: This is gonna be a tough one. On one hand, the massive SFMR errors in the 160-170 kt range and standard FL conversions could support a decrease all the way down to 145 kt. On the other hand, consistent 160-175 kt unflagged SFMR measurements are hard to ignore, and dropsondes suggested that FL winds (~160 kt in all quadrants) were mixing well due to air sinking all the way down to the surface near peak intensity. A reduction to 150-155 kt (with high uncertainty) seems most likely.

-Laura: 130 kt looks good

-Eta: No way this is getting upgraded even by 5 kt.

-Iota: Yeah it’s stuck at 135 kt.

-Ida: While arguments for 135 kt were valid a few months ago, the SFMR errors mean the NHC will judge it pretty much entirely based on FL conversions, so it’ll likely stay at 130 kt

-Sam: First peak didn’t have SFMR measurements to question because there was no recon coverage for its first peak. The second peak is probably not going to be increased.
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Re: Discussion of Intense Tropical Cyclones

#667 Postby Yellow Evan » Sun Nov 21, 2021 2:53 pm

aspen wrote:

Michael should be okay, because its Cat 5 upgrade was justified by standard FL-to-surface wind conversions and radar velocities alongside SFMR. The storms at risk are those whose intensities were based mainly on SFMR.

-Matthew: The time has come

-Jose: They should stick with 135 kt to account for the gap in recon, although I doubt it got as strong as Sam.

-Irma: Potentially could see another knock down to 150 kt, which is better supported by standard FL conversions

-Maria: 150 kt seems okay but could be on thin ice. Its 145 kt landfall intensity in Dominica is supported by a verified 130 kt 10-minute sustained reading recorded on the island.

-Michael: As I said, radar and FL measurements still support 140 kt, maybe even 145 kt.

-Dorian: This is gonna be a tough one. On one hand, the massive SFMR errors in the 160-170 kt range and standard FL conversions could support a decrease all the way down to 145 kt. On the other hand, consistent 160-175 kt unflagged SFMR measurements are hard to ignore, and dropsondes suggested that FL winds (~160 kt in all quadrants) were mixing well due to air sinking all the way down to the surface near peak intensity. A reduction to 150-155 kt (with high uncertainty) seems most likely.

-Laura: 130 kt looks good

-Eta: No way this is getting upgraded even by 5 kt.

-Iota: Yeah it’s stuck at 135 kt.

-Ida: While arguments for 135 kt were valid a few months ago, the SFMR errors mean the NHC will judge it pretty much entirely based on FL conversions, so it’ll likely stay at 130 kt

-Sam: First peak didn’t have SFMR measurements to question because there was no recon coverage for its first peak. The second peak is probably not going to be increased.


Patricia and Megi lose their 180+ knot claims is the biggest change if this analysis holds up.
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Re: Discussion of Intense Tropical Cyclones

#668 Postby MarioProtVI » Sun Nov 21, 2021 2:57 pm

aspen wrote:

Michael should be okay, because its Cat 5 upgrade was justified by standard FL-to-surface wind conversions and radar velocities alongside SFMR. The storms at risk are those whose intensities were based mainly on SFMR.

-Matthew: The time has come

-Jose: They should stick with 135 kt to account for the gap in recon, although I doubt it got as strong as Sam.

-Irma: Potentially could see another knock down to 150 kt, which is better supported by standard FL conversions

-Maria: 150 kt seems okay but could be on thin ice. Its 145 kt landfall intensity in Dominica is supported by a verified 130 kt 10-minute sustained reading recorded on the island.

-Michael: As I said, radar and FL measurements still support 140 kt, maybe even 145 kt.

-Dorian: This is gonna be a tough one. On one hand, the massive SFMR errors in the 160-170 kt range and standard FL conversions could support a decrease all the way down to 145 kt. On the other hand, consistent 160-175 kt unflagged SFMR measurements are hard to ignore, and dropsondes suggested that FL winds (~160 kt in all quadrants) were mixing well due to air sinking all the way down to the surface near peak intensity. A reduction to 150-155 kt (with high uncertainty) seems most likely.

-Laura: 130 kt looks good

-Eta: No way this is getting upgraded even by 5 kt.

-Iota: Yeah it’s stuck at 135 kt.

-Ida: While arguments for 135 kt were valid a few months ago, the SFMR errors mean the NHC will judge it pretty much entirely based on FL conversions, so it’ll likely stay at 130 kt

-Sam: First peak didn’t have SFMR measurements to question because there was no recon coverage for its first peak. The second peak is probably not going to be increased.

In Iota’s case there’s a possibility that legit C5 winds (e.g FL probably just a bit over 155 kt which would convert down to 140 kt at the surface) were missed just prior to peak intensity when recon flew in - which is plausible given that the satellite presentation began to degrade on the eastern side slightly from wind shear when the FL/SFMR were recorded. Hence it probably was a very brief C5 albeit only for like an hour or two before recon got in - almost like Michael.
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Re: Discussion of Intense Tropical Cyclones

#669 Postby MarioProtVI » Sun Nov 21, 2021 2:59 pm

Yellow Evan wrote:
aspen wrote:

Michael should be okay, because its Cat 5 upgrade was justified by standard FL-to-surface wind conversions and radar velocities alongside SFMR. The storms at risk are those whose intensities were based mainly on SFMR.

-Matthew: The time has come

-Jose: They should stick with 135 kt to account for the gap in recon, although I doubt it got as strong as Sam.

-Irma: Potentially could see another knock down to 150 kt, which is better supported by standard FL conversions

-Maria: 150 kt seems okay but could be on thin ice. Its 145 kt landfall intensity in Dominica is supported by a verified 130 kt 10-minute sustained reading recorded on the island.

-Michael: As I said, radar and FL measurements still support 140 kt, maybe even 145 kt.

-Dorian: This is gonna be a tough one. On one hand, the massive SFMR errors in the 160-170 kt range and standard FL conversions could support a decrease all the way down to 145 kt. On the other hand, consistent 160-175 kt unflagged SFMR measurements are hard to ignore, and dropsondes suggested that FL winds (~160 kt in all quadrants) were mixing well due to air sinking all the way down to the surface near peak intensity. A reduction to 150-155 kt (with high uncertainty) seems most likely.

-Laura: 130 kt looks good

-Eta: No way this is getting upgraded even by 5 kt.

-Iota: Yeah it’s stuck at 135 kt.

-Ida: While arguments for 135 kt were valid a few months ago, the SFMR errors mean the NHC will judge it pretty much entirely based on FL conversions, so it’ll likely stay at 130 kt

-Sam: First peak didn’t have SFMR measurements to question because there was no recon coverage for its first peak. The second peak is probably not going to be increased.


Patricia and Megi lose their 180+ knot claims is the biggest change if this analysis holds up.

Patricia’s FL were insanely high (192 kt) so I doubt it dips below 180 kt.
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Re: Discussion of Intense Tropical Cyclones

#670 Postby Yellow Evan » Sun Nov 21, 2021 3:18 pm

MarioProtVI wrote:
Yellow Evan wrote:
aspen wrote:Michael should be okay, because its Cat 5 upgrade was justified by standard FL-to-surface wind conversions and radar velocities alongside SFMR. The storms at risk are those whose intensities were based mainly on SFMR.

-Matthew: The time has come

-Jose: They should stick with 135 kt to account for the gap in recon, although I doubt it got as strong as Sam.

-Irma: Potentially could see another knock down to 150 kt, which is better supported by standard FL conversions

-Maria: 150 kt seems okay but could be on thin ice. Its 145 kt landfall intensity in Dominica is supported by a verified 130 kt 10-minute sustained reading recorded on the island.

-Michael: As I said, radar and FL measurements still support 140 kt, maybe even 145 kt.

-Dorian: This is gonna be a tough one. On one hand, the massive SFMR errors in the 160-170 kt range and standard FL conversions could support a decrease all the way down to 145 kt. On the other hand, consistent 160-175 kt unflagged SFMR measurements are hard to ignore, and dropsondes suggested that FL winds (~160 kt in all quadrants) were mixing well due to air sinking all the way down to the surface near peak intensity. A reduction to 150-155 kt (with high uncertainty) seems most likely.

-Laura: 130 kt looks good

-Eta: No way this is getting upgraded even by 5 kt.

-Iota: Yeah it’s stuck at 135 kt.

-Ida: While arguments for 135 kt were valid a few months ago, the SFMR errors mean the NHC will judge it pretty much entirely based on FL conversions, so it’ll likely stay at 130 kt

-Sam: First peak didn’t have SFMR measurements to question because there was no recon coverage for its first peak. The second peak is probably not going to be increased.


Patricia and Megi lose their 180+ knot claims is the biggest change if this analysis holds up.

Patricia’s FL were insanely high (192 kt) so I doubt it dips below 180 kt.


Blending 158 SFMR and 90% of 192 SFMR doesn’t support anything more than 165 at time of Recon peak.
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Re: Discussion of Intense Tropical Cyclones

#671 Postby MarioProtVI » Sun Nov 21, 2021 4:14 pm

Yellow Evan wrote:
MarioProtVI wrote:
Yellow Evan wrote:
Patricia and Megi lose their 180+ knot claims is the biggest change if this analysis holds up.

Patricia’s FL were insanely high (192 kt) so I doubt it dips below 180 kt.


Blending 158 SFMR and 90% of 192 SFMR doesn’t support anything more than 165 at time of Recon peak.

It’s more then likely they just use the FL>SFMR conversion to justify at least 175 kt.
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Re: Discussion of Intense Tropical Cyclones

#672 Postby aspen » Sun Nov 21, 2021 6:23 pm

Yellow Evan wrote:
aspen wrote:

Michael should be okay, because its Cat 5 upgrade was justified by standard FL-to-surface wind conversions and radar velocities alongside SFMR. The storms at risk are those whose intensities were based mainly on SFMR.

-Matthew: The time has come

-Jose: They should stick with 135 kt to account for the gap in recon, although I doubt it got as strong as Sam.

-Irma: Potentially could see another knock down to 150 kt, which is better supported by standard FL conversions

-Maria: 150 kt seems okay but could be on thin ice. Its 145 kt landfall intensity in Dominica is supported by a verified 130 kt 10-minute sustained reading recorded on the island.

-Michael: As I said, radar and FL measurements still support 140 kt, maybe even 145 kt.

-Dorian: This is gonna be a tough one. On one hand, the massive SFMR errors in the 160-170 kt range and standard FL conversions could support a decrease all the way down to 145 kt. On the other hand, consistent 160-175 kt unflagged SFMR measurements are hard to ignore, and dropsondes suggested that FL winds (~160 kt in all quadrants) were mixing well due to air sinking all the way down to the surface near peak intensity. A reduction to 150-155 kt (with high uncertainty) seems most likely.

-Laura: 130 kt looks good

-Eta: No way this is getting upgraded even by 5 kt.

-Iota: Yeah it’s stuck at 135 kt.

-Ida: While arguments for 135 kt were valid a few months ago, the SFMR errors mean the NHC will judge it pretty much entirely based on FL conversions, so it’ll likely stay at 130 kt

-Sam: First peak didn’t have SFMR measurements to question because there was no recon coverage for its first peak. The second peak is probably not going to be increased.


Patricia and Megi lose their 180+ knot claims is the biggest change if this analysis holds up.

Patricia’s TCR mentioned that the reconstructed SFMR readings from the two flights were considered reliable at the time. Therefore, the NHC will have to re-analyze these readings again, and try to see how well winds were translating down to the surface. FL conversion still supports winds of 200+ mph. What wind speed is supported by KCZ with a pressure of 872mb?

I don’t know much about Megi’s recon flights nor the analysis of its data, but I do know that Megi is not officially ~180 kt according to the JTWC — at least, that’s what Wikipedia would suggest.
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Re: Discussion of Intense Tropical Cyclones

#673 Postby Yellow Evan » Sun Nov 21, 2021 7:12 pm

MarioProtVI wrote:
Yellow Evan wrote:
MarioProtVI wrote:Patricia’s FL were insanely high (192 kt) so I doubt it dips below 180 kt.


Blending 158 SFMR and 90% of 192 SFMR doesn’t support anything more than 165 at time of Recon peak.

It’s more then likely they just use the FL>SFMR conversion to justify at least 175 kt.


Perhaps but NHC is definitely justified if they go down to 165 at peak if the bias figures from the presentation is exactly correct.
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Re: Discussion of Intense Tropical Cyclones

#674 Postby Yellow Evan » Sun Nov 21, 2021 7:19 pm

aspen wrote:
Yellow Evan wrote:
aspen wrote:Michael should be okay, because its Cat 5 upgrade was justified by standard FL-to-surface wind conversions and radar velocities alongside SFMR. The storms at risk are those whose intensities were based mainly on SFMR.

-Matthew: The time has come

-Jose: They should stick with 135 kt to account for the gap in recon, although I doubt it got as strong as Sam.

-Irma: Potentially could see another knock down to 150 kt, which is better supported by standard FL conversions

-Maria: 150 kt seems okay but could be on thin ice. Its 145 kt landfall intensity in Dominica is supported by a verified 130 kt 10-minute sustained reading recorded on the island.

-Michael: As I said, radar and FL measurements still support 140 kt, maybe even 145 kt.

-Dorian: This is gonna be a tough one. On one hand, the massive SFMR errors in the 160-170 kt range and standard FL conversions could support a decrease all the way down to 145 kt. On the other hand, consistent 160-175 kt unflagged SFMR measurements are hard to ignore, and dropsondes suggested that FL winds (~160 kt in all quadrants) were mixing well due to air sinking all the way down to the surface near peak intensity. A reduction to 150-155 kt (with high uncertainty) seems most likely.

-Laura: 130 kt looks good

-Eta: No way this is getting upgraded even by 5 kt.

-Iota: Yeah it’s stuck at 135 kt.

-Ida: While arguments for 135 kt were valid a few months ago, the SFMR errors mean the NHC will judge it pretty much entirely based on FL conversions, so it’ll likely stay at 130 kt

-Sam: First peak didn’t have SFMR measurements to question because there was no recon coverage for its first peak. The second peak is probably not going to be increased.


Patricia and Megi lose their 180+ knot claims is the biggest change if this analysis holds up.

Patricia’s TCR mentioned that the reconstructed SFMR readings from the two flights were considered reliable at the time. Therefore, the NHC will have to re-analyze these readings again, and try to see how well winds were translating down to the surface. FL conversion still supports winds of 200+ mph. What wind speed is supported by KCZ with a pressure of 872mb?

I don’t know much about Megi’s recon flights nor the analysis of its data, but I do know that Megi is not officially ~180 kt according to the JTWC — at least, that’s what Wikipedia would suggest.


CKZ supports 185 for 872 pressure.

Reprocessed with the 2015-2021 SFMR, Megi had SFMR’s of 187 knots and FL winds for Megi was 192(?) knots. Even the old SFMR algorithm had 171 knots. JTWC getting intensity estimates wrong is nothing new.
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Re: Discussion of Intense Tropical Cyclones

#675 Postby NotoSans » Tue Nov 23, 2021 11:16 pm

James Franklin did mention that the SFMR bias on the presentation slides were only preliminary and likely a bit high. NHC was given a set of adjustment that was slightly smaller for operational use in 2021. Operational intensity estimates for intense storms (e.g. Ida and Sam) had likely taken that into account already.
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Re: Discussion of Intense Tropical Cyclones

#676 Postby NotoSans » Wed Dec 01, 2021 11:26 am

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Re: Discussion of Intense Tropical Cyclones

#677 Postby Kingarabian » Wed Dec 01, 2021 3:01 pm


There's cases in where SAR was pretty bad in the EPAC and Atlantic. It could be doing better in the WPAC due to systems there naturally being larger in size.
Last edited by Kingarabian on Wed Dec 01, 2021 3:07 pm, edited 2 times in total.
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Re: Discussion of Intense Tropical Cyclones

#678 Postby Kingarabian » Wed Dec 01, 2021 3:04 pm

Yellow Evan wrote:
aspen wrote:
Yellow Evan wrote:
Patricia and Megi lose their 180+ knot claims is the biggest change if this analysis holds up.

Patricia’s TCR mentioned that the reconstructed SFMR readings from the two flights were considered reliable at the time. Therefore, the NHC will have to re-analyze these readings again, and try to see how well winds were translating down to the surface. FL conversion still supports winds of 200+ mph. What wind speed is supported by KCZ with a pressure of 872mb?

I don’t know much about Megi’s recon flights nor the analysis of its data, but I do know that Megi is not officially ~180 kt according to the JTWC — at least, that’s what Wikipedia would suggest.


CKZ supports 185 for 872 pressure.

Reprocessed with the 2015-2021 SFMR, Megi had SFMR’s of 187 knots and FL winds for Megi was 192(?) knots. Even the old SFMR algorithm had 171 knots. JTWC getting intensity estimates wrong is nothing new.


I think the NHC will keep Patricia's intensity the same if CKZ supports 185kts, FL level winds support 200mph, and when factoring recon could've missed Patricia's lowest pressure reading.
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Re: Discussion of Intense Tropical Cyclones

#679 Postby Audrey2Katrina » Tue Dec 07, 2021 1:39 am

Teban54 wrote:

Have to say the bias is even greater than I thought, and more than enough to justify the Iota downgrade.


Frankly, I was convinced since last year that Iota was NEVER a Cat 5-- and even though it's not an "intense" storm...I'm equally convinced Zeta was no major at all.
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Re: Discussion of Intense Tropical Cyclones

#680 Postby Foxfires » Tue Dec 07, 2021 9:33 am

Okay this is unrelated to what's currently being discussed but I was wondering what everyone's intensity estimates for these typhoons are and if you agree with the JMA's estimate.

Image
Typhoon Nelson 1988. The JMA estimated peak intensity at 915mb.

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Typhoon Gordon. The JMA estimated peak intensity at 915mb.

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Typhoon Andy 1989. The JMA estimated peak intensity at 920mb.

There're probably other satellite pics like microwave imagery that would help but I can't find those anywhere.
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