Hurricane Laura’s intensity at landfall

[Shell Mound]

Officially, the NHC estimates that Laura made landfall just east of Calcasieu Pass, Louisiana, with one-minute, 10-m maximum sustained winds (MSW) of 130 kt. However, an extensive survey conducted by Structural Extreme Events Reconnaissance (StEER) found that the peak gusts along the immediate shoreline only reached ~122 kt in Creole, the location of the peak measured storm tide of 17.1 ft above ground level (AGL). StEER used an extensive network of StickNet stations installed and manned by Texas Tech University and also performed widespread assessments of structural damage. The NWS in Lake Charles even relied on StEER’s analysis to develop its own wind-based charts for Laura. Another interesting point is that StEER’s report (p. 17) mentioned that the lowest MSLP recorded at Calcasieu Pass was 945 mb, whereas the NHC’s TCR (p. 5) mentions that it was 940 mb, and coincided with winds of 11 kt inside the eye (RMW). According to the NWS a site ~19 n mi inland from and north-northwest of Calcasieu Pass recorded a minimum MSLP of 946 mb. Given the large size of the eye and proximity to water Laura likely would not have filled much between those two points. From p. 41 of the StEER report:



Taken together, along with the fact that objective Dvorak estimates were only around ~115 kt at landfall, does this indicate Laura was much weaker than 130 kt?

Thoughts welcome.

[tolakram]

I don't think so, but one day it may be re-analyzed. What does it matter?

[Iceresistance]

Officially, the NHC estimates that Laura made landfall just east of Calcasieu Pass, Louisiana, with one-minute, 10-m maximum sustained winds (MSW) of 130 kt. However, an extensive survey conducted by Structural Extreme Events Reconnaissance (StEER) found that the peak gusts along the immediate shoreline only reached ~122 kt in Creole, the location of the peak measured storm tide of 17.1 ft above ground level (AGL). StEER used an extensive network of StickNet stations installed and manned by Texas Tech University and also performed widespread assessments of structural damage. The NWS in Lake Charles even relied on StEER’s analysis to develop its own wind-based charts for Laura. Another interesting point is that StEER’s report (p. 17) mentioned that the lowest MSLP recorded at Calcasieu Pass was 945 mb, whereas the NHC’s TCR (p. 5) mentions that it was 940 mb, and coincided with winds of 11 kt inside the eye (RMW). According to the NWS a site ~19 n mi inland from and north-northwest of Calcasieu Pass recorded a minimum MSLP of 946 mb. Given the large size of the eye and proximity to water Laura likely would not have filled much between those two points. From p. 41 of the StEER report:

https://i.ibb.co/g9mC0XN/Ska-rmavbild-2021-08-13-kl-12-57-08.png

Taken together, along with the fact that objective Dvorak estimates were only around ~115 kt at landfall, does this indicate Laura was much weaker than 130 kt?

Thoughts welcome.

Dvorak estimates are usually not very accurate in the Atlantic . . . They had Dorian as a minimal CAT 5 in 2019 when it really was at 185 mph . . . (I don't have the GIF because I was tracking it elsewhere . . .)

[Shell Mound]

Officially, the NHC estimates that Laura made landfall just east of Calcasieu Pass, Louisiana, with one-minute, 10-m maximum sustained winds (MSW) of 130 kt. However, an extensive survey conducted by Structural Extreme Events Reconnaissance (StEER) found that the peak gusts along the immediate shoreline only reached ~122 kt in Creole, the location of the peak measured storm tide of 17.1 ft above ground level (AGL). StEER used an extensive network of StickNet stations installed and manned by Texas Tech University and also performed widespread assessments of structural damage. The NWS in Lake Charles even relied on StEER’s analysis to develop its own wind-based charts for Laura. Another interesting point is that StEER’s report (p. 17) mentioned that the lowest MSLP recorded at Calcasieu Pass was 945 mb, whereas the NHC’s TCR (p. 5) mentions that it was 940 mb, and coincided with winds of 11 kt inside the eye (RMW). According to the NWS a site ~19 n mi inland from and north-northwest of Calcasieu Pass recorded a minimum MSLP of 946 mb. Given the large size of the eye and proximity to water Laura likely would not have filled much between those two points. From p. 41 of the StEER report:

https://i.ibb.co/g9mC0XN/Ska-rmavbild-2021-08-13-kl-12-57-08.png

Taken together, along with the fact that objective Dvorak estimates were only around ~115 kt at landfall, does this indicate Laura was much weaker than 130 kt?

Thoughts welcome.

Dvorak estimates are usually not very accurate in the Atlantic . . . They had Dorian as a minimal CAT 5 in 2019 when it really was at 185 mph . . . (I don't have the GIF because I was tracking it elsewhere . . .)

Some estimates suggest that Dorian may have been roughly 15 kt weaker than its officially estimated MSW of 160 kt. The highest measured 700-mb (flight-level) winds supported one-minute, 10-m winds of ~145 kt, comparable to Andrew’s estimated MSW at landfall in South Florida. Radar-derived data aside, a combination of FL, SFMR, and Dvorak estimates suggests that Michael may have been on the order of 125–135 kt at landfall, rather than 140 kt. As far as Laura is concerned, I am wondering why the very comprehensive survey failed to find evidence of MSW even close to 130 kt, even in the area along the immediate shoreline that was sited within the “right-front” RMW. Getting the intensity right is essential to managing public perception and safety in the future, as well as vital to historical records’ veracity.

[AlphaToOmega]

Officially, the NHC estimates that Laura made landfall just east of Calcasieu Pass, Louisiana, with one-minute, 10-m maximum sustained winds (MSW) of 130 kt. However, an extensive survey conducted by Structural Extreme Events Reconnaissance (StEER) found that the peak gusts along the immediate shoreline only reached ~122 kt in Creole, the location of the peak measured storm tide of 17.1 ft above ground level (AGL). StEER used an extensive network of StickNet stations installed and manned by Texas Tech University and also performed widespread assessments of structural damage. The NWS in Lake Charles even relied on StEER’s analysis to develop its own wind-based charts for Laura. Another interesting point is that StEER’s report (p. 17) mentioned that the lowest MSLP recorded at Calcasieu Pass was 945 mb, whereas the NHC’s TCR (p. 5) mentions that it was 940 mb, and coincided with winds of 11 kt inside the eye (RMW). According to the NWS a site ~19 n mi inland from and north-northwest of Calcasieu Pass recorded a minimum MSLP of 946 mb. Given the large size of the eye and proximity to water Laura likely would not have filled much between those two points. From p. 41 of the StEER report:

https://i.ibb.co/g9mC0XN/Ska-rmavbild-2021-08-13-kl-12-57-08.png

Taken together, along with the fact that objective Dvorak estimates were only around ~115 kt at landfall, does this indicate Laura was much weaker than 130 kt?

Thoughts welcome.

Dvorak estimates are usually not very accurate in the Atlantic . . . They had Dorian as a minimal CAT 5 in 2019 when it really was at 185 mph . . . (I don't have the GIF because I was tracking it elsewhere . . .)

Some estimates suggest that Dorian may have been roughly 15 kt weaker than its officially estimated MSW of 160 kt. The highest measured 700-mb (flight-level) winds supported one-minute, 10-m winds of ~145 kt, comparable to Andrew’s estimated MSW at landfall in South Florida. Radar-derived data aside, a combination of FL, SFMR, and Dvorak estimates suggests that Michael may have been on the order of 125–135 kt at landfall, rather than 140 kt. As far as Laura is concerned, I am wondering why the very comprehensive survey failed to find evidence of MSW even close to 130 kt, even in the area along the immediate shoreline that was sited within the “right-front” RMW. Getting the intensity right is essential to managing public perception and safety in the future, as well as vital to historical records’ veracity.

Dvorak seems to have a tendency to underestimate powerful storms in the Atlantic.

[JetFuel_SE]

Officially, the NHC estimates that Laura made landfall just east of Calcasieu Pass, Louisiana, with one-minute, 10-m maximum sustained winds (MSW) of 130 kt. However, an extensive survey conducted by Structural Extreme Events Reconnaissance (StEER) found that the peak gusts along the immediate shoreline only reached ~122 kt in Creole, the location of the peak measured storm tide of 17.1 ft above ground level (AGL). StEER used an extensive network of StickNet stations installed and manned by Texas Tech University and also performed widespread assessments of structural damage. The NWS in Lake Charles even relied on StEER’s analysis to develop its own wind-based charts for Laura. Another interesting point is that StEER’s report (p. 17) mentioned that the lowest MSLP recorded at Calcasieu Pass was 945 mb, whereas the NHC’s TCR (p. 5) mentions that it was 940 mb, and coincided with winds of 11 kt inside the eye (RMW). According to the NWS a site ~19 n mi inland from and north-northwest of Calcasieu Pass recorded a minimum MSLP of 946 mb. Given the large size of the eye and proximity to water Laura likely would not have filled much between those two points. From p. 41 of the StEER report:

https://i.ibb.co/g9mC0XN/Ska-rmavbild-2021-08-13-kl-12-57-08.png

Taken together, along with the fact that objective Dvorak estimates were only around ~115 kt at landfall, does this indicate Laura was much weaker than 130 kt?

Thoughts welcome.

Dvorak estimates are usually not very accurate in the Atlantic . . . They had Dorian as a minimal CAT 5 in 2019 when it really was at 185 mph . . . (I don't have the GIF because I was tracking it elsewhere . . .)

Some estimates suggest that Dorian may have been roughly 15 kt weaker than its officially estimated MSW of 160 kt. The highest measured 700-mb (flight-level) winds supported one-minute, 10-m winds of ~145 kt, comparable to Andrew’s estimated MSW at landfall in South Florida. Radar-derived data aside, a combination of FL, SFMR, and Dvorak estimates suggests that Michael may have been on the order of 125–135 kt at landfall, rather than 140 kt. As far as Laura is concerned, I am wondering why the very comprehensive survey failed to find evidence of MSW even close to 130 kt, even in the area along the immediate shoreline that was sited within the “right-front” RMW. Getting the intensity right is essential to managing public perception and safety in the future, as well as vital to historical records’ veracity.

Force Thirteen is not a reliable source.

[HurricaneEnzo]

One potential issue I see with 'sticknet' is the height at which they are recording these winds. The WMO height for wind measurement is 10m (33feet). Those sticknet stations look to be no more than a few feet high. I haven't looked too far into this. Maybe they compensate for that factor but could cause some discrepancy. I also don't claim to know how much discrepancy it would cause just pointing it out as a potential issue.

[Category5Kaiju]

Dvorak estimates are usually not very accurate in the Atlantic . . . They had Dorian as a minimal CAT 5 in 2019 when it really was at 185 mph . . . (I don't have the GIF because I was tracking it elsewhere . . .)

Some estimates suggest that Dorian may have been roughly 15 kt weaker than its officially estimated MSW of 160 kt. The highest measured 700-mb (flight-level) winds supported one-minute, 10-m winds of ~145 kt, comparable to Andrew’s estimated MSW at landfall in South Florida. Radar-derived data aside, a combination of FL, SFMR, and Dvorak estimates suggests that Michael may have been on the order of 125–135 kt at landfall, rather than 140 kt. As far as Laura is concerned, I am wondering why the very comprehensive survey failed to find evidence of MSW even close to 130 kt, even in the area along the immediate shoreline that was sited within the “right-front” RMW. Getting the intensity right is essential to managing public perception and safety in the future, as well as vital to historical records’ veracity.

Force Thirteen is not a reliable source.

If I remember correctly Force Thirteen has like their own estimates for peak intensities of specific storms that are deviant from what the NOAA and NHC officially measure (for instance, they estimated Felicia this year to be a 165 mph, 932 mbar hurricane). So yeah, I know many wx enthusiasts flock to that channel and watch their storm videos, but in terms of factual accuracy, I am not sure if that's a source one should rely on (even Wikipedia has a disclaimer that they do not allow info from Force Thirteen to be written in their pages). Force Thirteen if I recall correctly is not run by accredited and experienced meteorologists or scientists but rather from wx enthusiasts.

[Iceresistance]

Some estimates suggest that Dorian may have been roughly 15 kt weaker than its officially estimated MSW of 160 kt. The highest measured 700-mb (flight-level) winds supported one-minute, 10-m winds of ~145 kt, comparable to Andrew’s estimated MSW at landfall in South Florida. Radar-derived data aside, a combination of FL, SFMR, and Dvorak estimates suggests that Michael may have been on the order of 125–135 kt at landfall, rather than 140 kt. As far as Laura is concerned, I am wondering why the very comprehensive survey failed to find evidence of MSW even close to 130 kt, even in the area along the immediate shoreline that was sited within the “right-front” RMW. Getting the intensity right is essential to managing public perception and safety in the future, as well as vital to historical records’ veracity.

Force Thirteen is not a reliable source.

If I remember correctly Force Thirteen has like their own estimates for peak intensities of specific storms that are deviant from what the NOAA and NHC officially measure (for instance, they estimated Felicia this year to be a 165 mph, 932 mbar hurricane). So yeah, I know many wx enthusiasts flock to that channel and watch their storm videos, but in terms of factual accuracy, I am not sure if that's a source one should rely on (even Wikipedia has a disclaimer that they do not allow info from Force Thirteen to be written in their pages). Force Thirteen if I recall correctly is not run by accredited and experienced meteorologists or scientists but rather from wx enthusiasts.

I don't either, I'd take their forecasts as a grain of salt . . .

They overestimate intensities it seems . . .

[JetFuel_SE]

Force Thirteen is not a reliable source.

If I remember correctly Force Thirteen has like their own estimates for peak intensities of specific storms that are deviant from what the NOAA and NHC officially measure (for instance, they estimated Felicia this year to be a 165 mph, 932 mbar hurricane). So yeah, I know many wx enthusiasts flock to that channel and watch their storm videos, but in terms of factual accuracy, I am not sure if that's a source one should rely on (even Wikipedia has a disclaimer that they do not allow info from Force Thirteen to be written in their pages). Force Thirteen if I recall correctly is not run by accredited and experienced meteorologists or scientists but rather from wx enthusiasts.

I don't either, I'd take their forecasts as a grain of salt . . .

They overestimate intensities it seems . . .

At least they now have Matthew as a C4.

[Shell Mound]

Some estimates suggest that Dorian may have been roughly 15 kt weaker than its officially estimated MSW of 160 kt. The highest measured 700-mb (flight-level) winds supported one-minute, 10-m winds of ~145 kt, comparable to Andrew’s estimated MSW at landfall in South Florida. Radar-derived data aside, a combination of FL, SFMR, and Dvorak estimates suggests that Michael may have been on the order of 125–135 kt at landfall, rather than 140 kt. As far as Laura is concerned, I am wondering why the very comprehensive survey failed to find evidence of MSW even close to 130 kt, even in the area along the immediate shoreline that was sited within the “right-front” RMW. Getting the intensity right is essential to managing public perception and safety in the future, as well as vital to historical records’ veracity.

Force Thirteen is not a reliable source.

If I remember correctly Force Thirteen has like their own estimates for peak intensities of specific storms that are deviant from what the NOAA and NHC officially measure (for instance, they estimated Felicia this year to be a 165 mph, 932 mbar hurricane).

Force Thirteen’s assessment of Felicia is actually well considered and scientifically valid. It definitely highlights the shortcomings of the Dvorak technique in relation to small systems. However, Laura was a large system, so Dvorak would have been more accurate. Does anyone have an answer as to why StEER’s survey only found wind-caused damage indicative of gusts ≤ 122 kt, even within the RMW and along the immediate shoreline in the vicinity of Creole, Louisiana?

[Chris90]

Measuring peak wind gusts on land and attempting to survey wind damage to determine what the actual peak winds experienced on land was is a fool's errand in my opinion. You have to take so many things into consideration and wind gusts and variations in wind are so extremely localized that the chance of measuring the actual peak gust is extraordinarily small.

We had a severe storm either last summer or this one, I can't remember (I'm a Midwesterner, they start to run together), and wind gusts at my location were roughly 60-70mph. Someone had left a plastic cup sitting on my deck railing. This empty plastic cup survived an entire storm with those gusts without moving an inch on that railing. It had a trellis behind it acting as a windbreak so it wasn't taking the beating. If I had set up an an anemometer there I would have barely received anything as opposed to setting it up in an open area of my backyard. I know professionals usually try to set up their instrumentation in the best possible areas to get accurate readings, but there's only so much you can do.

Surveying damage has the same problem because you have to survey all the damage which isn't going to happen, that's too big of a task, and it's subject to the massive problem of human error and bias. Wind damage can vary so significantly over small distances that the surveyor can easily miss the most intense areas and no 2 surveyors are going to analyze it the same. I mean we literally see people on this site analyze and interpret data differently every single day, it's just part of being human. One survey team is going to come up with a different solution than another team does.

I think the best thing we can do when it comes to peak winds at landfall for tropical cyclones is utilize radar and make estimates based off that as to what peak winds reaching the surface would be utilizing velocity data and correlating it with the depth and strength of the convection at the time to make an educated guess as to how efficiently winds are mixing to the surface and how frequently peak wind gusts are making it there. But land based measurements only cover such a small area that measuring the peak wind is almost impossible, it would literally be pure luck to capture, and surveys are subject to human error and bias. I mean, it's still valuable data, but I wouldn't utilize just that.

As Laura approached the coast she produced a 223 mph measurement on radar, surrounded by 6 bins >200mph. It was almost certainly associated with a mesovortex, but that's still going to be enhancing surface winds. A dropsonde measured 179kts as it descended in the eyewall. I don't know that these stronger measurements ever made it to the surface, but I'd bet wind gusts exceeding 122kts made it to the surface more than once as Laura made landfall.

[Audrey2Katrina]

Dvorak seems to have a tendency to underestimate powerful storms in the Atlantic.

He cited much more than just Dvorak... Just saying!

[Yellow Evan]

Force Thirteen is not a reliable source.

If I remember correctly Force Thirteen has like their own estimates for peak intensities of specific storms that are deviant from what the NOAA and NHC officially measure (for instance, they estimated Felicia this year to be a 165 mph, 932 mbar hurricane).

Force Thirteen’s assessment of Felicia is actually well considered and scientifically valid. It definitely highlights the shortcomings of the Dvorak technique in relation to small systems. However, Laura was a large system, so Dvorak would have been more accurate. Does anyone have an answer as to why StEER’s survey only found wind-caused damage indicative of gusts ≤ 122 kt, even within the RMW and along the immediate shoreline in the vicinity of Creole, Louisiana?

As for Felicia the F13 piece is mostly rambling about processes not solely related to the storm, brings up its excellent microwave presentation and argues that based on Recon data from Isabel, which was a very different storm, that Felicia overran Dvorak intensity estimates significantly. As for Laura, why should we trust StEER damage surveys over the 148 FL and 137 SFMR that Recon found? Dvorak should also not be used when Recon is present because Recon is ground truth and Dvorak is not.