Storms that were upgraded to and downgraded from Cat 5

[Tekken_Guy]

What storms were upgraded to Category 5 despite not being that way operationally? And what storms didn’t reach Category 5 after being initially believed to have done so?

[aspen]

I think a storm from pre-1970 was originally assessed as a Cat 5 but then downgraded in post-analysis a few years ago. I don’t recall the name, though.

[Chris90]

I think a storm from pre-1970 was originally assessed as a Cat 5 but then downgraded in post-analysis a few years ago. I don’t recall the name, though.

I think you're thinking of hurricane Carla of '61. Originally assessed at 150kts, downgraded to 125kts in 2018 with reanalysis.

[aspen]

I think a storm from pre-1970 was originally assessed as a Cat 5 but then downgraded in post-analysis a few years ago. I don’t recall the name, though.

I think you're thinking of hurricane Carla of '61. Originally assessed at 150kts, downgraded to 125kts in 2018 with reanalysis.

Yep, that’s the one. That is a massive downgrade and I wonder why they made that decision. Where can I find the NHC’s report on it?

[Chris90]

I think a storm from pre-1970 was originally assessed as a Cat 5 but then downgraded in post-analysis a few years ago. I don’t recall the name, though.

I think you're thinking of hurricane Carla of '61. Originally assessed at 150kts, downgraded to 125kts in 2018 with reanalysis.

Yep, that’s the one. That is a massive downgrade and I wonder why they made that decision. Where can I find the NHC’s report on it?

Here's a short summary of some reanalysis, I didn't read through everything so I might have missed it, but they don't explicitly mention the previous intensity of 150kts and why they reduced it, they just mention how they settled on 125kts from the bit I read.
https://www.google.com/url?sa=t&source= ... MMvJzZyq-_

You might also find this interesting, a video of the presentation for the 60s reanalysis.

https://ams.confex.com/ams/33HURRICANE/ ... 39830.html


Also of note is that Esther of '61 got upgraded to Cat 5, with a boost from 125kts to 140kts and Hurricane Inez of '66 got an upgrade to Cat 5 as well, boosted to 145kts from 130kts previously.

[Audrey2Katrina]

Hurricane Andrew in 1992 was a Cat 4 for about 10 or 15 years, then they promoted it to a 5.

I can see re-evaluating a storm within a window of a few years; but I think what they did to Carla, which I remember and she was a MONSTER, I feel, is just to subjective, and being nearly 60 years after the fact... I just don't buy it. I know it changes nothing; but I think these subjective (and they are that) opinions should have stronger reasons than what I've seen so far. Audrey down to a 3, Betsy up to a 4... these are storms MORE than 56-65 years ago... so much more instrumentation now for sure; but I read reports from some of those storms and to just say "Nope--you guys were wrong--we're gonna re-write the report half a century later! I just think it's too subjective. Re-assess storms within say a 10 year window with today's technologies is fine... going back half a century is a bit much but-- they're the experts so it is what it is.

A2K

[Shell Mound]

I think a storm from pre-1970 was originally assessed as a Cat 5 but then downgraded in post-analysis a few years ago. I don’t recall the name, though.

I think you're thinking of hurricane Carla of '61. Originally assessed at 150kts, downgraded to 125kts in 2018 with reanalysis.

Yep, that’s the one. That is a massive downgrade and I wonder why they made that decision. Where can I find the NHC’s report on it?

According to the reanalysis, Carla’s minimum central pressure ranged from 927–934 mb between 06:00 UTC on 10 September and 21:15 UTC (the time of landfall in TX) on 11 September, based on observations from reconnaissance, vessels, and land-based stations. During this timeframe, aircraft- and land-based radar indicated an inner eye that ranged from 30 to 40 n mi in diameter, suggesting an RMW of ~20 to 30 n mi (compared to an average value of ~15 n mi for Carla’s coordinates). At the time the cyclone was quite large and moving at a slower-than-average pace. Originally, HURDAT listed a MSW of 150 kt at 06:00 UTC on 11 September, coincident with the 927-mb reading from aircraft. By comparison, Katrina (2005) at its peak of 150 kt featured an eye diameter of 22–25 n mi, coincident with flight-level (700-mb) winds of 166 kt (90% reduction: 149 kt) and a MSLP of 902–907 mb. Katrina was comparable to Carla in size at the time, including that of its eye, yet its MSLP was far lower, it was well sampled by aircraft during its peak, and data from aircraft did not support 1-min, 10-m MSW higher than 150 kt. So I think Carla’s revised peak MSW of 125 kt is reasonable, both prior to during landfall, given that Katrina was analogous but barely managed 150 kt despite having a far lower MSLP. Carla, incidentally, was also well sampled by aircraft, ship, and land-based station(s) on 10–11 September.

I can see re-evaluating a storm within a window of a few years; but I think what they did to Carla, which I remember and she was a MONSTER, I feel, is just to subjective, and being nearly 60 years after the fact... I just don't buy it.

As I noted above, Carla’s downgrade, even decades “after the fact,” seems fairly reasonable, given that Katrina was similar but was far deeper at 150 kt.

[TheAustinMan]

There wasn't much of an operational record at the time, but HURDAT lists the sixth hurricane of 1870 as a Category 3 hurricane, while Chenoweth's 2014 compilation of 1851-1898 Atlantic storms lists it as a Category 5 hurricane, apparently due to a 914 mbar peripheral pressure reading while the hurricane was in the Florida Straits. There are also several new storms in the Chenoweth reconstruction over the central and eastern Atlantic during this era, so it's worth checking out.

Aside from Andrew, Carla, and Inez (the latter of which has not been formalized), and within the more recent record:

Hurricane Dog of 1950 used to be a quite powerful 160-kt Category 5, and quite a long-lasting one, within the Sargasso Sea between Bermuda and the Greater Antilles. Pressures in the 930s and 940s during this window suggested to the HURDAT reanalysis project that Dog peaked at around 125 kt, making it a Category 4.
Hurricane Carol of 1953 used to be listed as a 130-kt Category 4, but is now listed as a 140-kt Category 5 northeast of the Virgin Islands, given its small size and 929 mbar. The HURDAT reanalysis project notes that Carol's structure may have been similar to Andrew or 2007's Felix during this time, with a radius of maximum winds only 3 nmi across.
Hurricane Donna of 1960 used to be listed as a 140-kt Category 5 on its approach towards the West Indies. However, with pressures in the 950s, the HURDAT reanalysis considered Donna was more likely a Category 3 during this time. It is now thought that Donna was stronger north of Hispaniola and near Florida - as a 120 or 125 kt Category 4 - than it ever was over the Central Atlantic.
Hurricane Ethel of 1960 used to be known for having an unusually high pressure (in the 970s millibars) while also being a Category 5 (in fact Ethel's Cat 5 classification was paired with a 981 mb presure). Observations suggest that Ethel did have somewhat high pressures for its intensity, but 970s-980s are way, way too high to plausibly support a Category 5. Ethel is now listed as a 100-kt Category 3.
Hurricane Esther of 1961 was upgraded from a 125-kt Category 4 hurricane to a 140-kt Category 5 hurricane north of Puerto Rico, based on an evaluation of a 919 mbar central pressure observed by a research mission from the National Hurricane Research Project.

There is a research paper by Andrew Hagen and Chris Landsea, On the Classification of Extreme Atlantic Hurricanes Utilizing Mid-Twentieth-Century Monitoring Capabilities (2012), which uses 10 recent Category 5 hurricanes and hypothesizes what these would look like if we were limited to the observational capabilities and coverage of the late 1940s and early 1950s. It's worth noting that a lot of these are lower because recon generally did not fly into the centers of storms with pressures below ~940 mb until the late 1950s, and because they only flew in the daytime.
54 KB.


More recently, 2005's Hurricane Emily was upgraded from a 135-kt high-end Category 4 to a 140-kt Category 5 in the post-season based on 153 kt winds observed by reconnaissance at 700 mb, which translated to around 138 kt at the surface. Similarly, 2018's Hurricane Michael, operationally listed as a 135-kt Category 4, was upgraded to a 140-kt Category 5 in the post-season based on several factors, including a very similar 152-kt 700mb wind, radar analyses pointing to an intensity of possibly 145 kt, and reconstructions of the wind field suggesting a 135-140 kt intensity.

[Audrey2Katrina]

I think you're thinking of hurricane Carla of '61. Originally assessed at 150kts, downgraded to 125kts in 2018 with reanalysis.

Yep, that’s the one. That is a massive downgrade and I wonder why they made that decision. Where can I find the NHC’s report on it?

According to the reanalysis, Carla’s minimum central pressure ranged from 927–934 mb between 06:00 UTC on 10 September and 21:15 UTC (the time of landfall in TX) on 11 September, based on observations from reconnaissance, vessels, and land-based stations. During this timeframe, aircraft- and land-based radar indicated an inner eye that ranged from 30 to 40 n mi in diameter, suggesting an RMW of ~20 to 30 n mi (compared to an average value of ~15 n mi for Carla’s coordinates). At the time the cyclone was quite large and moving at a slower-than-average pace. Originally, HURDAT listed a MSW of 150 kt at 06:00 UTC on 11 September, coincident with the 927-mb reading from aircraft. By comparison, Katrina (2005) at its peak of 150 kt featured an eye diameter of 22–25 n mi, coincident with flight-level (700-mb) winds of 166 kt (90% reduction: 149 kt) and a MSLP of 902–907 mb. Katrina was comparable to Carla in size at the time, including that of its eye, yet its MSLP was far lower, it was well sampled by aircraft during its peak, and data from aircraft did not support 1-min, 10-m MSW higher than 150 kt. So I think Carla’s revised peak MSW of 125 kt is reasonable, both prior to during landfall, given that Katrina was analogous but barely managed 150 kt despite having a far lower MSLP. Carla, incidentally, was also well sampled by aircraft, ship, and land-based station(s) on 10–11 September.

I can see re-evaluating a storm within a window of a few years; but I think what they did to Carla, which I remember and she was a MONSTER, I feel, is just to subjective, and being nearly 60 years after the fact... I just don't buy it.

As I noted above, Carla’s downgrade, even decades “after the fact,” seems fairly reasonable, given that Katrina was similar but was far deeper at 150 kt.

Basing it on storms of similar size and what their MSLP's were doesn't always apply... additionally, Katrina was not the the same size as Carla which I remember as a MUCH larger storm, and while it's not an accepted measure Carla is still ranked #1 on the HSI index. You really just can't say that "well this pressure was about the same and it had lower winds"... Katrina's MSW were about 152 kt from what I read, I don't have it before me; but that's what I remember. You're going to drop a storm fifty-seven years later, by 25 kt because a "similar" storm (still smaller) had a lower central pressure? Well, Katrina and Laura were "similar" in size too... but Laura's MSLP was 937 hPa. Katrina's at landfall was 919, but Laura had MSW of 132 kt, with a pressure nearly 20 hPa higher than Katrina which only had 109kt.? (This just doesn't jive with the size-pressure similarity necessitates similar max winds.) Remember, they didn't have the instrumentation in 1961 that we have now and I know that means the data could go either way-- however I still think it was an overly subjective decision and while I know it won't change a thing. I don't buy it. Not more than half a century after the fact.

A2K

[Shell Mound]

Yep, that’s the one. That is a massive downgrade and I wonder why they made that decision. Where can I find the NHC’s report on it?

According to the reanalysis, Carla’s minimum central pressure ranged from 927–934 mb between 06:00 UTC on 10 September and 21:15 UTC (the time of landfall in TX) on 11 September, based on observations from reconnaissance, vessels, and land-based stations. During this timeframe, aircraft- and land-based radar indicated an inner eye that ranged from 30 to 40 n mi in diameter, suggesting an RMW of ~20 to 30 n mi (compared to an average value of ~15 n mi for Carla’s coordinates). At the time the cyclone was quite large and moving at a slower-than-average pace. Originally, HURDAT listed a MSW of 150 kt at 06:00 UTC on 11 September, coincident with the 927-mb reading from aircraft. By comparison, Katrina (2005) at its peak of 150 kt featured an eye diameter of 22–25 n mi, coincident with flight-level (700-mb) winds of 166 kt (90% reduction: 149 kt) and a MSLP of 902–907 mb. Katrina was comparable to Carla in size at the time, including that of its eye, yet its MSLP was far lower, it was well sampled by aircraft during its peak, and data from aircraft did not support 1-min, 10-m MSW higher than 150 kt. So I think Carla’s revised peak MSW of 125 kt is reasonable, both prior to during landfall, given that Katrina was analogous but barely managed 150 kt despite having a far lower MSLP. Carla, incidentally, was also well sampled by aircraft, ship, and land-based station(s) on 10–11 September.

I can see re-evaluating a storm within a window of a few years; but I think what they did to Carla, which I remember and she was a MONSTER, I feel, is just to subjective, and being nearly 60 years after the fact... I just don't buy it.

As I noted above, Carla’s downgrade, even decades “after the fact,” seems fairly reasonable, given that Katrina was similar but was far deeper at 150 kt.

Basing it on storms of similar size and what their MSLP's were doesn't always apply... additionally, Katrina was not the the same size as Carla which I remember as a MUCH larger storm, and while it's not an accepted measure Carla is still ranked #1 on the HSI index. You really just can't say that "well this pressure was about the same and it had lower winds"... Katrina's MSW were about 152 kt from what I read, I don't have it before me; but that's what I remember. You're going to drop a storm fifty-seven years later, by 25 kt because a "similar" storm (still smaller) had a lower central pressure? Well, Katrina and Laura were "similar" in size too... but Laura's MSLP was 937 hPa. Katrina's at landfall was 919, but Laura had MSW of 132 kt, with a pressure nearly 20 hPa higher than Katrina which only had 109kt.? (This just doesn't jive with the size-pressure similarity necessitates similar max winds.) Remember, they didn't have the instrumentation in 1961 that we have now and I know that means the data could go either way-- however I still think it was an overly subjective decision and while I know it won't change a thing. I don't buy it. Not more than half a century after the fact.

A2K

If Carla was even larger than Katrina, then the odds that its MSW were lower than Katrina’s increases, based on the reasoning that I enumerated. In general, storms with relatively broad wind fields embedded in low environmental pressures while moving at slower-than-average paces tend to require lower pressures to attain certain maximum sustained wind velocities. This reasoning is regarded as scientific and is used by the NHC and the Best Track Committee. As far as Laura is concerned, the NHC’s advisories indicate that it was smaller than Katrina, based on its radius of hurricane-force winds:

Hurricane-force winds extend outward up to 60 miles (95 km) from
the center and tropical-storm-force winds extend outward up to 205
miles (335 km).

Source

By contrast, Katrina at its peak intensity:

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 105 MILES FROM THE
CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP
TO 205 MILES.

Source

[storm_in_a_teacup]

Mostly I am sad about Carla because the whole original character I created for her (which you could see in that “Harvey Diaries” post I placed on this site several years ago) was predicated on the fact she was a category 5 hurricane. Once they downgraded her the personality and abilities I gave her don’t quite seem as elegantly appropriate...

It’s kind of like the downgrade of Pluto, which does make perfect sense scientifically, but it still made me mad on an emotional level.

(On a related note I am kind of dreading the James Webb Space Telescope brutally murdering my favorite hypothesis about supermassive black hole formation.)

[NXStumpy_Robothing]

Mostly I am sad about Carla because the whole original character I created for her (which you could see in that “Harvey Diaries” post I placed on this site several years ago) was predicated on the fact she was a category 5 hurricane. Once they downgraded her the personality and abilities I gave her don’t quite seem as elegantly appropriate...

It’s kind of like the downgrade of Pluto, which does make perfect sense scientifically, but it still made me mad on an emotional level.

(On a related note I am kind of dreading the James Webb Space Telescope brutally murdering my favorite hypothesis about supermassive black hole formation.)

Bold of you to assume that telescope is ever launched.

Relating to Carla more specifically, it seems like landfall observations indicated that it was in the middle of an EWRC at landfall, and so that matches the revised HURDAT track at that point. However, since data is still somewhat sparse even as recently as 1961, and high-end hurricanes have a tendency to fluctuate relatively quickly, I wouldn't be surprised for it to have reached Category 5 intensity at some point, even though it will probably never be recorded as such. So your imagined personality of the storm is probably safe for future generations, albeit with an asterisk

[Audrey2Katrina]

According to the reanalysis, Carla’s minimum central pressure ranged from 927–934 mb between 06:00 UTC on 10 September and 21:15 UTC (the time of landfall in TX) on 11 September, based on observations from reconnaissance, vessels, and land-based stations. During this timeframe, aircraft- and land-based radar indicated an inner eye that ranged from 30 to 40 n mi in diameter, suggesting an RMW of ~20 to 30 n mi (compared to an average value of ~15 n mi for Carla’s coordinates). At the time the cyclone was quite large and moving at a slower-than-average pace. Originally, HURDAT listed a MSW of 150 kt at 06:00 UTC on 11 September, coincident with the 927-mb reading from aircraft. By comparison, Katrina (2005) at its peak of 150 kt featured an eye diameter of 22–25 n mi, coincident with flight-level (700-mb) winds of 166 kt (90% reduction: 149 kt) and a MSLP of 902–907 mb. Katrina was comparable to Carla in size at the time, including that of its eye, yet its MSLP was far lower, it was well sampled by aircraft during its peak, and data from aircraft did not support 1-min, 10-m MSW higher than 150 kt. So I think Carla’s revised peak MSW of 125 kt is reasonable, both prior to during landfall, given that Katrina was analogous but barely managed 150 kt despite having a far lower MSLP. Carla, incidentally, was also well sampled by aircraft, ship, and land-based station(s) on 10–11 September.


As I noted above, Carla’s downgrade, even decades “after the fact,” seems fairly reasonable, given that Katrina was similar but was far deeper at 150 kt.

Basing it on storms of similar size and what their MSLP's were doesn't always apply... additionally, Katrina was not the the same size as Carla which I remember as a MUCH larger storm, and while it's not an accepted measure Carla is still ranked #1 on the HSI index. You really just can't say that "well this pressure was about the same and it had lower winds"... Katrina's MSW were about 152 kt from what I read, I don't have it before me; but that's what I remember. You're going to drop a storm fifty-seven years later, by 25 kt because a "similar" storm (still smaller) had a lower central pressure? Well, Katrina and Laura were "similar" in size too... but Laura's MSLP was 937 hPa. Katrina's at landfall was 919, but Laura had MSW of 132 kt, with a pressure nearly 20 hPa higher than Katrina which only had 109kt.? (This just doesn't jive with the size-pressure similarity necessitates similar max winds.) Remember, they didn't have the instrumentation in 1961 that we have now and I know that means the data could go either way-- however I still think it was an overly subjective decision and while I know it won't change a thing. I don't buy it. Not more than half a century after the fact.

A2K

If Carla was even larger than Katrina, then the odds that its MSW were lower than Katrina’s increases, based on the reasoning that I enumerated. In general, storms with relatively broad wind fields embedded in low environmental pressures while moving at slower-than-average paces tend to require lower pressures to attain certain maximum sustained wind velocities. This reasoning is regarded as scientific and is used by the NHC and the Best Track Committee. As far as Laura is concerned, the NHC’s advisories indicate that it was smaller than Katrina, based on its radius of hurricane-force winds:

Hurricane-force winds extend outward up to 60 miles (95 km) from
the center and tropical-storm-force winds extend outward up to 205
miles (335 km).

Source

By contrast, Katrina at its peak intensity:

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 105 MILES FROM THE
CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP
TO 205 MILES.

Source

So now we're bringing size as a reason to downgrade her. Hmmm... Betsy was HUGE... 50 mile wide eye... upgraded to Cat 4. And by YOUR source, both Laura and Katrina had windfields of Tropical storms extending 205 miles out. Like I said, they were similar... I wish we could see the actual wind field of Carla other than land "guesstimates" as they didn't have doppler radar, satellite and 24 hour flights into the storm. Again, Laura had approximately the same windfield as Katrina--using your "source" going out to tropical storm wind field. Dropsondes showed that one area just before landfall near Pass Christian showed winds approaching 200 mph. I do not buy the large "must" be lower in winds. Additionally, Hurricanes are categorized by their maximum winds, and lowest MSLP throughout their path. A pressure of 902 is more than 30 hPa below the 937 of Laura--that's pretty deep. Regardless of size. Even at landfall, still 20 hPa below that of Laura at Landfall.. the storms were using your own words about Carla and Katrina "of similar size. I can't cite Carla's vs Katrina's without digging up a LOT of old research because I can't find the archives that far back (I'm sure I can somewhere) Betsy's eye was 50 MILES wide and yet they upgraded her to a 4-- her windfield was huge too. Again, my contention is that there are too many variables to make that kind of assumption. Storms pre-satellite data and those post are difficult to compare without a LOT of speculation. And the report is rife with "estimate" and "assume", and "best guess" which I know are very well intended and researched -- but in the final analysis, still just "speculation" they had a Cat 5 storm (I'm winging it here but I know I read it in an NHC report, that had lowest pressure in the upper 960's... so as I said MULTIPLE times... I'm NOT buying that Carla dropped by 25 kt based on speculation and "estimations" made sixty years after the fact. Is it possible she was a 4... sure... and it's possible she was a 5 based on data from that time... we will never truly know beyond any shadow of a doubt. It's also probable (if not likely) that Katrina came in as a Cat 4 and not a Cat 3. *I* think it's likely that Laura was a Cat 3 and not a Cat 4 (gasp) I can hear them from here. I had a friend whose house was not more than 20 miles from landfall and the eye passed over him... NE quadrant. It was bad, terrible... but I don't think consistent with sustained cat 5 winds (and it was, according to the report, coming in at 132 kt sustained. Bottom line... too much speculation. I'm obviously not going to change your mind, and you aren't going to change mine. This is what makes the discussions on this board so interesting. Pax!

A2K

[Shell Mound]

Basing it on storms of similar size and what their MSLP's were doesn't always apply... additionally, Katrina was not the the same size as Carla which I remember as a MUCH larger storm, and while it's not an accepted measure Carla is still ranked #1 on the HSI index. You really just can't say that "well this pressure was about the same and it had lower winds"... Katrina's MSW were about 152 kt from what I read, I don't have it before me; but that's what I remember. You're going to drop a storm fifty-seven years later, by 25 kt because a "similar" storm (still smaller) had a lower central pressure? Well, Katrina and Laura were "similar" in size too... but Laura's MSLP was 937 hPa. Katrina's at landfall was 919, but Laura had MSW of 132 kt, with a pressure nearly 20 hPa higher than Katrina which only had 109kt.? (This just doesn't jive with the size-pressure similarity necessitates similar max winds.) Remember, they didn't have the instrumentation in 1961 that we have now and I know that means the data could go either way-- however I still think it was an overly subjective decision and while I know it won't change a thing. I don't buy it. Not more than half a century after the fact.

A2K

If Carla was even larger than Katrina, then the odds that its MSW were lower than Katrina’s increases, based on the reasoning that I enumerated. In general, storms with relatively broad wind fields embedded in low environmental pressures while moving at slower-than-average paces tend to require lower pressures to attain certain maximum sustained wind velocities. This reasoning is regarded as scientific and is used by the NHC and the Best Track Committee. As far as Laura is concerned, the NHC’s advisories indicate that it was smaller than Katrina, based on its radius of hurricane-force winds:

Hurricane-force winds extend outward up to 60 miles (95 km) from
the center and tropical-storm-force winds extend outward up to 205
miles (335 km).

Source

By contrast, Katrina at its peak intensity:

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 105 MILES FROM THE
CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP
TO 205 MILES.

Source

So now we're bringing size as a reason to downgrade her. Hmmm... Betsy was HUGE... 50 mile wide eye... upgraded to Cat 4. And by YOUR source, both Laura and Katrina had windfields of Tropical storms extending 205 miles out. Like I said, they were similar... I wish we could see the actual wind field of Carla other than land "guesstimates" as they didn't have doppler radar, satellite and 24 hour flights into the storm. Again, Laura had approximately the same windfield as Katrina--using your "source" going out to tropical storm wind field. Dropsondes showed that one area just before landfall near Pass Christian showed winds approaching 200 mph. I do not buy the large "must" be lower in winds. Additionally, Hurricanes are categorized by their maximum winds, and lowest MSLP throughout their path. A pressure of 902 is more than 30 hPa below the 937 of Laura--that's pretty deep. Regardless of size. Even at landfall, still 20 hPa below that of Laura at Landfall.. the storms were using your own words about Carla and Katrina "of similar size. I can't cite Carla's vs Katrina's without digging up a LOT of old research because I can't find the archives that far back (I'm sure I can somewhere) Betsy's eye was 50 MILES wide and yet they upgraded her to a 4-- her windfield was huge too. Again, my contention is that there are too many variables to make that kind of assumption. Storms pre-satellite data and those post are difficult to compare without a LOT of speculation. And the report is rife with "estimate" and "assume", and "best guess" which I know are very well intended and researched -- but in the final analysis, still just "speculation" they had a Cat 5 storm (I'm winging it here but I know I read it in an NHC report, that had lowest pressure in the upper 960's... so as I said MULTIPLE times... I'm NOT buying that Carla dropped by 25 kt based on speculation and "estimations" made sixty years after the fact. Is it possible she was a 4... sure... and it's possible she was a 5 based on data from that time... we will never truly know beyond any shadow of a doubt. It's also probable (if not likely) that Katrina came in as a Cat 4 and not a Cat 3. *I* think it's likely that Laura was a Cat 3 and not a Cat 4 (gasp) I can hear them from here. I had a friend whose house was not more than 20 miles from landfall and the eye passed over him... NE quadrant. It was bad, terrible... but I don't think consistent with sustained cat 5 winds (and it was, according to the report, coming in at 132 kt sustained. Bottom line... too much speculation. I'm obviously not going to change your mind, and you aren't going to change mine. This is what makes the discussions on this board so interesting. Pax!

A2K

Incidentally, I happen to concur that Laura’s intensity at landfall was likely overestimated. The maximum flight-level (700-mb) wind recorded closest to landfall was 142 kt in the strongest quadrant, but that reading coincided with SFMR of just 113 kt, albeit flagged. SFMR tends to inflate surface winds while over shallow, nearshore waters such as the Gulf coastal shelf. However, according to p. 7 of its TCR, the highest SFMR measured in Katrina near the time of landfall was only 96 kt, and there was little evidence from reconnaissance to justify the official BT MSW of 110 kt at landfall. If Laura was not a Cat-4 at LF, then I personally struggle to see how Katrina could have been, given the relative dearth of corroboration from reconnaissance as well as Katrina’s degraded radar/satellite signature during LF. Per the following tweet, the winds in Laura were apparently mixing to the surface rather well, even during landfall, but I suspect that both SFMR and sondes tend to overestimate 10-m winds over shallow water:

 https://twitter.com/N8_Snyder/status/1298838299377840128




Personally, I still consider Audrey to have been a far worse event for Southwestern Louisiana than Laura, and I suspect that further reanalysis would reconfirm its original Cat-4 status at LF. If anything, I think Audrey’s actual intensity at LF may have been closer to Cat-5 status than indicated in the original BT, which, prior to reanalysis, listed MSW of 125 kt and MSLP of 946 mb at LF, both of which I believe underestimate Audrey’s true intensity. I think Audrey was closer to 130–135 kt at LF with a pressure in the low to mid 920s. Carla (1961) likely featured a very similar intensity at landfall, only with a slightly higher MSLP, in the upper 920s; my own estimate would be 135 kt / 927 mb. I would personally put Camille (1969) at 155 kt / 895 mb for its LF just west of Waveland, MS, near Clermont Harbor. Both Celia (1970) and Eloise (1975), along with Betsy (1965), were likely on the order of 120–125 kt with a MSLP in the low 940s at LF.

[DestinHurricane]

If Carla was even larger than Katrina, then the odds that its MSW were lower than Katrina’s increases, based on the reasoning that I enumerated. In general, storms with relatively broad wind fields embedded in low environmental pressures while moving at slower-than-average paces tend to require lower pressures to attain certain maximum sustained wind velocities. This reasoning is regarded as scientific and is used by the NHC and the Best Track Committee. As far as Laura is concerned, the NHC’s advisories indicate that it was smaller than Katrina, based on its radius of hurricane-force winds:

Source

By contrast, Katrina at its peak intensity:

Source

So now we're bringing size as a reason to downgrade her. Hmmm... Betsy was HUGE... 50 mile wide eye... upgraded to Cat 4. And by YOUR source, both Laura and Katrina had windfields of Tropical storms extending 205 miles out. Like I said, they were similar... I wish we could see the actual wind field of Carla other than land "guesstimates" as they didn't have doppler radar, satellite and 24 hour flights into the storm. Again, Laura had approximately the same windfield as Katrina--using your "source" going out to tropical storm wind field. Dropsondes showed that one area just before landfall near Pass Christian showed winds approaching 200 mph. I do not buy the large "must" be lower in winds. Additionally, Hurricanes are categorized by their maximum winds, and lowest MSLP throughout their path. A pressure of 902 is more than 30 hPa below the 937 of Laura--that's pretty deep. Regardless of size. Even at landfall, still 20 hPa below that of Laura at Landfall.. the storms were using your own words about Carla and Katrina "of similar size. I can't cite Carla's vs Katrina's without digging up a LOT of old research because I can't find the archives that far back (I'm sure I can somewhere) Betsy's eye was 50 MILES wide and yet they upgraded her to a 4-- her windfield was huge too. Again, my contention is that there are too many variables to make that kind of assumption. Storms pre-satellite data and those post are difficult to compare without a LOT of speculation. And the report is rife with "estimate" and "assume", and "best guess" which I know are very well intended and researched -- but in the final analysis, still just "speculation" they had a Cat 5 storm (I'm winging it here but I know I read it in an NHC report, that had lowest pressure in the upper 960's... so as I said MULTIPLE times... I'm NOT buying that Carla dropped by 25 kt based on speculation and "estimations" made sixty years after the fact. Is it possible she was a 4... sure... and it's possible she was a 5 based on data from that time... we will never truly know beyond any shadow of a doubt. It's also probable (if not likely) that Katrina came in as a Cat 4 and not a Cat 3. *I* think it's likely that Laura was a Cat 3 and not a Cat 4 (gasp) I can hear them from here. I had a friend whose house was not more than 20 miles from landfall and the eye passed over him... NE quadrant. It was bad, terrible... but I don't think consistent with sustained cat 5 winds (and it was, according to the report, coming in at 132 kt sustained. Bottom line... too much speculation. I'm obviously not going to change your mind, and you aren't going to change mine. This is what makes the discussions on this board so interesting. Pax!

A2K

Incidentally, I happen to concur that Laura’s intensity at landfall was likely overestimated. The maximum flight-level (700-mb) wind recorded closest to landfall was 142 kt in the strongest quadrant, but that reading coincided with SFMR of just 113 kt, albeit flagged. SFMR tends to inflate surface winds while over shallow, nearshore waters such as the Gulf coastal shelf. However, according to p. 7 of its TCR, the highest SFMR measured in Katrina near the time of landfall was only 96 kt, and there was little evidence from reconnaissance to justify the official BT MSW of 110 kt at landfall. If Laura was not a Cat-4 at LF, then I personally struggle to see how Katrina could have been, given the relative dearth of corroboration from reconnaissance as well as Katrina’s degraded radar/satellite signature during LF. Per the following tweet, the winds in Laura were apparently mixing to the surface rather well, even during landfall, but I suspect that both SFMR and sondes tend to overestimate 10-m winds over shallow water:

https://twitter.com/N8_Snyder/status/1298838299377840128

Personally, I still consider Audrey to have been a far worse event for Southwestern Louisiana than Laura, and I suspect that further reanalysis would reconfirm its original Cat-4 status at LF. If anything, I think Audrey’s actual intensity at LF may have been closer to Cat-5 status than indicated in the original BT, which, prior to reanalysis, listed MSW of 125 kt and MSLP of 946 mb at LF, both of which I believe underestimate Audrey’s true intensity. I think Audrey was closer to 130–135 kt at LF with a pressure in the low to mid 920s. Carla (1961) likely featured a very similar intensity at landfall, only with a slightly higher MSLP, in the upper 920s; my own estimate would be 135 kt / 927 mb. I would personally put Camille (1969) at 155 kt / 895 mb for its LF just west of Waveland, MS, near Clermont Harbor. Both Celia (1970) and Eloise (1975), along with Betsy (1965), were likely on the order of 120–125 kt with a MSLP in the low 940s at LF.

I agree about Eloise. Had a cleared out eye with blue skies and the strongest quadrant had no wind samples. the 155 mph gust was east of the strongest winds. The 955 was measured at the edge of the eye in destin, there was no pressure measured in santa rosa beach where the center of the eye moved.

[Audrey2Katrina]

Incidentally, I happen to concur that Laura’s intensity at landfall was likely overestimated. The maximum flight-level (700-mb) wind recorded closest to landfall was 142 kt in the strongest quadrant, but that reading coincided with SFMR of just 113 kt, albeit flagged. SFMR tends to inflate surface winds while over shallow, nearshore waters such as the Gulf coastal shelf. However, according to p. 7 of its [report] the highest SFMR measured in Katrina near the time of landfall was only 96 kt, and there was little evidence from reconnaissance to justify the official BT MSW of 110 kt at landfall. If Laura was not a Cat-4 at LF, then I personally struggle to see how Katrina could have been, given the relative dearth of corroboration from reconnaissance as well as Katrina’s degraded radar/satellite signature during LF. Per the following tweet, the winds in Laura were apparently mixing to the surface rather well, even during landfall, but I suspect that both SFMR and sondes tend to overestimate 10-m winds over shallow water:



Personally, I still consider Audrey to have been a far worse event for Southwestern Louisiana than Laura, and I suspect that further reanalysis would reconfirm its original Cat-4 status at LF. If anything, I think Audrey’s actual intensity at LF may have been closer to Cat-5 status than indicated in the original BT, which, prior to reanalysis, listed MSW of 125 kt and MSLP of 946 mb at LF, both of which I believe underestimate Audrey’s true intensity. I think Audrey was closer to 130–135 kt at LF with a pressure in the low to mid 920s. Carla (1961) likely featured a very similar intensity at landfall, only with a slightly higher MSLP, in the upper 920s; my own estimate would be 135 kt / 927 mb. I would personally put Camille (1969) at 155 kt / 895 mb for its LF just west of Waveland, MS, near Clermont Harbor. Both Celia (1970) and Eloise (1975), along with Betsy (1965), were likely on the order of 120–125 kt with a MSLP in the low 940s at LF.

We could argue this silly "My hurricane was worse than yours" stuff all night and this is one reason I took a many year hiatus from these boards much as I like meteorology. There was NO working instrument to measure top wind speeds of Katrina when it made landfall... the anemometer at Grand Isle, closest to first landfall, was completely demolished more than two hours before landfall. The Buras water tower (and it's not small) was blown completely on top of another building. The landfalling pressure of 919 was the lowest seen given only a 110 kt landfall since Floyd made landfall at 110kt with a 930 mb pressure. It still is the lowest recorded landfalling pressure with a max est. WS of 110 kt. As far as using p.7 of the report... let's cite it in a better context:

...the strongest surface (10m) wind measured by dropwindsonde on the morning of 29
August was 99 kt from two separate sondes. The maximum surface wind estimate from a
dropwindsonde, derived from the mean wind over the lowest 150 m of the sounding using an
average adjustment derived from profiles in several storms, was 98 kt. However, analysis of
several dropwindsonde profiles from 29 August suggests that a slightly different adjustment
could have been valid that day. This difference would result in 10 m wind estimates derived
from the lowest 150 m of the dropwindsonde profiles being 3-5 kt stronger, or up to about 103
kt. The maximum surface wind measured by the SFMR on 29 August was 96 kt just after 1200
UTC. The best track intensity of Katrina at 1200 UTC 29 August, shortly after the initial
Louisiana landfall when the central pressure was 923 mb, has been adjusted downward
in poststorm analysis to 110 kt from the operationally assessed value of 120 kt. The Buras, LA landfall
intensity about one hour earlier has also been estimated at 110 kt, when the central pressure was
only slightly lower at 920 mb. This estimate is still about 10% greater than the maximum
surface winds from the dropwindsondes and SFMR, accounting for the possibility that these
instruments did not sample the maximum wind. It is worth noting that Katrina was likely at
Category 4 strength with maximum sustained winds of about 115 kt near 0900 UTC 29 August, a
couple of hours before the center made landfall near Buras, LA. Due to the large (~25-30 n mi)
radius of maximum winds, it is possible that sustained winds of Category 4 strength briefly
impacted the extreme southeastern tip of Louisiana in advance of landfall of the center.

How do they justify making Laura 150 mph (133kt) when there was no consistent data on land or from flight reconnaissance to substantiate that--it was all "subjective" estimates--and in 2005, where Katrina came in for first landfall virtually every land-based instrument had failed well before the eye got there.. that's also in the report. Winds of 108 kt (gust) were reported as far out as Pascagoula, well over 170 miles away from landfall... not even Laura can lay claim to anything approaching that. Katrina's pressure was still in the 920's when it crossed the La./Ms border. I had a friend on the Gulfport Police dept. who used his doppler radar gun (granted not exactly a meteorological instruments) and he has photos of it showing winds in excess of 140 mph. I don't really care what people care to believe, to be perfectly honest; but boy if you could've seen the raging discussions I had back in 2005-2006 with folks incessantly determined to show how THEIR storm was worse than Mine... (I've never understood that mentality) frankly I KNOW that the worst storm I personally went through, for me, was Betsy. I was a little too far from tightly packed Camille, although I well remember her too. And with all due respect, as far as one meteorology student (and I do NOT say that disparagingly as that's what I might have loved to do in another time and life!) claiming winds of 142kt from ONE dropsonde.. why not use the ONE ship that measured winds of over 168 mph in Audrey? Why not the one dropsonde not in the report but that I distinctly remember reading showing a wind of over 200 mph at an altitude of 150 feet near Pass Christian Mississippi--no I don't have the picture of it, and it's not in the report; but I sure wish I'd have kept it because it was real. That's the problem... every one says Oh there's a dearth of information on Katrina... ya think? maybe because it came in over a VERY sparsely populated wetland for the first 100 or so miles? Or maybe because they didn't have the sophistication we have now? I don't care if Katrina is reclassified as a one... the biggest joke of all, in MY opinion. was them reclassifying Zeta, as a 3! Talk about a "dearth of evidence"! Having rode out both I can assure you Katrina was many times worse than anything Zeta was. -- That said... I agree with you on Laura vs. Audrey-- I've been saying that for months. But neither you nor I will make this decision.. it will be made by the folks at the NHC whether I like it... or you like it, whether I agree with it or not, or you agree with it or not. And that's what makes even "official" documents---get called into question betimes---and sometimes that can be fun. No offense intended to you or anyone else--sometimes when I get to typing... my fingers go faster than my mind...PAX

A2K

[CrazyC83]

There wasn't much of an operational record at the time, but HURDAT lists the sixth hurricane of 1870 as a Category 3 hurricane, while Chenoweth's 2014 compilation of 1851-1898 Atlantic storms lists it as a Category 5 hurricane, apparently due to a 914 mbar peripheral pressure reading while the hurricane was in the Florida Straits. There are also several new storms in the Chenoweth reconstruction over the central and eastern Atlantic during this era, so it's worth checking out.

Aside from Andrew, Carla, and Inez (the latter of which has not been formalized), and within the more recent record:

Hurricane Dog of 1950 used to be a quite powerful 160-kt Category 5, and quite a long-lasting one, within the Sargasso Sea between Bermuda and the Greater Antilles. Pressures in the 930s and 940s during this window suggested to the HURDAT reanalysis project that Dog peaked at around 125 kt, making it a Category 4.
Hurricane Carol of 1953 used to be listed as a 130-kt Category 4, but is now listed as a 140-kt Category 5 northeast of the Virgin Islands, given its small size and 929 mbar. The HURDAT reanalysis project notes that Carol's structure may have been similar to Andrew or 2007's Felix during this time, with a radius of maximum winds only 3 nmi across.
Hurricane Donna of 1960 used to be listed as a 140-kt Category 5 on its approach towards the West Indies. However, with pressures in the 950s, the HURDAT reanalysis considered Donna was more likely a Category 3 during this time. It is now thought that Donna was stronger north of Hispaniola and near Florida - as a 120 or 125 kt Category 4 - than it ever was over the Central Atlantic.
Hurricane Ethel of 1960 used to be known for having an unusually high pressure (in the 970s millibars) while also being a Category 5 (in fact Ethel's Cat 5 classification was paired with a 981 mb presure). Observations suggest that Ethel did have somewhat high pressures for its intensity, but 970s-980s are way, way too high to plausibly support a Category 5. Ethel is now listed as a 100-kt Category 3.
Hurricane Esther of 1961 was upgraded from a 125-kt Category 4 hurricane to a 140-kt Category 5 hurricane north of Puerto Rico, based on an evaluation of a 919 mbar central pressure observed by a research mission from the National Hurricane Research Project.

There is a research paper by Andrew Hagen and Chris Landsea, On the Classification of Extreme Atlantic Hurricanes Utilizing Mid-Twentieth-Century Monitoring Capabilities (2012), which uses 10 recent Category 5 hurricanes and hypothesizes what these would look like if we were limited to the observational capabilities and coverage of the late 1940s and early 1950s. It's worth noting that a lot of these are lower because recon generally did not fly into the centers of storms with pressures below ~940 mb until the late 1950s, and because they only flew in the daytime.
54 KB.
https://journals.ametsoc.org/view/journals/clim/25/13/full-jcli-d-11-00420.1-t1.jpg

More recently, 2005's Hurricane Emily was upgraded from a 135-kt high-end Category 4 to a 140-kt Category 5 in the post-season based on 153 kt winds observed by reconnaissance at 700 mb, which translated to around 138 kt at the surface. Similarly, 2018's Hurricane Michael, operationally listed as a 135-kt Category 4, was upgraded to a 140-kt Category 5 in the post-season based on several factors, including a very similar 152-kt 700mb wind, radar analyses pointing to an intensity of possibly 145 kt, and reconstructions of the wind field suggesting a 135-140 kt intensity.

Of the more recent category 5 storms, if they expanded that study to them, it is probable that Irma, Maria, Michael and Dorian would have all been category 5 even in the older era, based on the 915 mb surface observation in Barbuda for Irma, 143 kt surface observation in Roseau for Maria, 922 mb surface pressure (unknown if a central pressure - in reality it was not) for Michael and multiple pressure observations in the Bahamas for Dorian.

[Audrey2Katrina]

There wasn't much of an operational record at the time, but HURDAT lists the sixth hurricane of 1870 as a Category 3 hurricane, while Chenoweth's 2014 compilation of 1851-1898 Atlantic storms lists it as a Category 5 hurricane, apparently due to a 914 mbar peripheral pressure reading while the hurricane was in the Florida Straits. There are also several new storms in the Chenoweth reconstruction over the central and eastern Atlantic during this era, so it's worth checking out.

Aside from Andrew, Carla, and Inez (the latter of which has not been formalized), and within the more recent record:

Hurricane Dog of 1950 used to be a quite powerful 160-kt Category 5, and quite a long-lasting one, within the Sargasso Sea between Bermuda and the Greater Antilles. Pressures in the 930s and 940s during this window suggested to the HURDAT reanalysis project that Dog peaked at around 125 kt, making it a Category 4.
Hurricane Carol of 1953 used to be listed as a 130-kt Category 4, but is now listed as a 140-kt Category 5 northeast of the Virgin Islands, given its small size and 929 mbar. The HURDAT reanalysis project notes that Carol's structure may have been similar to Andrew or 2007's Felix during this time, with a radius of maximum winds only 3 nmi across.
Hurricane Donna of 1960 used to be listed as a 140-kt Category 5 on its approach towards the West Indies. However, with pressures in the 950s, the HURDAT reanalysis considered Donna was more likely a Category 3 during this time. It is now thought that Donna was stronger north of Hispaniola and near Florida - as a 120 or 125 kt Category 4 - than it ever was over the Central Atlantic.
Hurricane Ethel of 1960 used to be known for having an unusually high pressure (in the 970s millibars) while also being a Category 5 (in fact Ethel's Cat 5 classification was paired with a 981 mb presure). Observations suggest that Ethel did have somewhat high pressures for its intensity, but 970s-980s are way, way too high to plausibly support a Category 5. Ethel is now listed as a 100-kt Category 3.
Hurricane Esther of 1961 was upgraded from a 125-kt Category 4 hurricane to a 140-kt Category 5 hurricane north of Puerto Rico, based on an evaluation of a 919 mbar central pressure observed by a research mission from the National Hurricane Research Project.

There is a research paper by Andrew Hagen and Chris Landsea, On the Classification of Extreme Atlantic Hurricanes Utilizing Mid-Twentieth-Century Monitoring Capabilities (2012), which uses 10 recent Category 5 hurricanes and hypothesizes what these would look like if we were limited to the observational capabilities and coverage of the late 1940s and early 1950s. It's worth noting that a lot of these are lower because recon generally did not fly into the centers of storms with pressures below ~940 mb until the late 1950s, and because they only flew in the daytime.
54 KB.
https://journals.ametsoc.org/view/journals/clim/25/13/full-jcli-d-11-00420.1-t1.jpg

More recently, 2005's Hurricane Emily was upgraded from a 135-kt high-end Category 4 to a 140-kt Category 5 in the post-season based on 153 kt winds observed by reconnaissance at 700 mb, which translated to around 138 kt at the surface. Similarly, 2018's Hurricane Michael, operationally listed as a 135-kt Category 4, was upgraded to a 140-kt Category 5 in the post-season based on several factors, including a very similar 152-kt 700mb wind, radar analyses pointing to an intensity of possibly 145 kt, and reconstructions of the wind field suggesting a 135-140 kt intensity.

Of the more recent category 5 storms, if they expanded that study to them, it is probable that Irma, Maria, Michael and Dorian would have all been category 5 even in the older era, based on the 915 mb surface observation in Barbuda for Irma, 143 kt surface observation in Roseau for Maria, 922 mb surface pressure (unknown if a central pressure - in reality it was not) for Michael and multiple pressure observations in the Bahamas for Dorian.

I like, and a agree with much of what you say; but size and spread of windfield have an awful lot to do with what the winds were. Katrina proved that: 919 landfall and barely a Cat 3. Having said that, I personally think there is something to be said for the Hurricane Severity Index. The HSI takes into account both intensity of the storm AND the size and spread of the windfield. I know the feud or for lack of a better word with those who favor the SS scale will never settle the issue; but I DO think a better method of classifying theses storms is possible. When Zeta becomes a 3 based on one or two bins over water, and these have a margin of error, there has to be a better means of classification. Until then, we can argue about what storm was what severity ad infinitum. I fully agree with your comments on Irma, Maria, and Dorian... I don't see how they could've NOT been Cat 5. But, it's still intriguing to think about what things are, or were that might differ from "official" records. PAX.

A2K