ATL: HELENE - Post-Tropical - Discussion

[Anti-freeze]

Gonna vent for a minute. The damage inland is awful, widespread, maybe even historic, as is the impact of so many bridge and road washouts, so there is no need to exaggerate. But we have the usual Twitter drama queens declaring that a town is 'Gone', 'Wiped out', 'Wiped off the map', etc. From all the years watching reports from tornado 'storm chasers', 99% of the time when they claim this it turns out to be bogus. Similarly I have yet to find a town in the mountains that is actually 'gone'. There may be, there's probably a lot of info that hasn't gotten out yet (I'm afraid the death count will increase) but so far we're approaching 'Bodies in the trees!' hyperbole from some, followed by FWD;FWD;FWD;....

So here's hopefully a more balanced look at the terrible destruction we know about so far. Towns that Twits have declared 'Gone':

Black Mountain, NC, damage from massive flooding, possible landslides:

https://x.com/Wh_So_Serious/status/1840146821966115070

Montreat, NC:

https://x.com/dyllan_bwell/status/1839894472932446361

Montreat College is still there, most dorms are fine and a dining hall is open:

https://www.montreat.edu/2024/09/update-on-tropical-storm-helene-impact/?fbclid=IwZXh0bgNhZW0CMTEAAR0kT9KTfHr1Yj_rGmMX841D5hdbFWrZmhY277Y5Ppg6EPHwbF0bG7OCBaE_aem_4W5oYM-r2jJ02YvKz-W6Zg

And while that repost of what a "Black Mountain police chief" alleged said could end up being legitimate, I can find no independent verification of any of it by a news organization, and all the tweets seem to trace back to a college student that is a weather enthusiast. So I won't link it here.

Chimney Rock, NC, some of the river side business are gone, bridges and roads washed out:

https://x.com/Notizia18894/status/1840062674073190498

https://www.youtube.com/watch?v=coDkfDBNhg8

In a different vein, a couple that just avoided a landslide while driving reacts (#ChampagneSupernova):

https://x.com/wibw/status/1840134640012534244

[blueskies]

Anyone with Cajun navy contacts in NC? Friend of mine is frantic to find her parents in the Sherwood Forest neighborhood of Cedar Mt, NC. Landslides were reported near their home. I knew there was a number around a few years back.

There is a facebook page for the United Cajun Navy Carolinas.

You could try contacting Cajun Navy 2016 / Pinnacle SAR at pinnaclesar.org or (833) 225-8616. Maybe they have contact information for the Carolinas.

There appear to be various organizations now using the term "cajun army" in their name.

[blueskies]

We plotted the max sustained wind and gusts for Helene and the results were similar to Idalia and Francine (and 2002's Lily, 2020's Zeta). There were no reports of sustained hurricane force wind (1 min avg) inland across Florida or Georgia. However, there were plenty of reports of 95-110 mph gusts all the way up to the SC border along its track. Inland, the experience was of a strong tropical storm with Cat 2-3 wind gusts. So, what happened?

Clearly, the plane found very strong wind aloft, and maybe there were Cat 4 winds at the surface at some point offshore. However, Lily, Zeta, Idalia, Francine and Helene encountered a SW-NE jet as they approached the coast. Initially, the jet enhanced outflow and helped each storm to strengthen offshore. What aids strengthening eventually becomes detrimental wind shear. In each of these storms, the surface wind became decoupled from the stronger wind aloft. The effect was to lower the sustained surface wind but allow those stronger winds aloft to dip down. Wind gusts were nearly twice the sustained surface wind. Double the wind, four times the wind force. It doesn't take a 1-min average 100-120 mph wind to cause damage, a 10-20 second gust will produce a similar result.

Next time, keep a close eye on the predicted wind aloft as a storm nears landfall. If it's going to be encountering a jet, particularly later in the season, watch for this effect. Early season storms usually don't have to contend with the Polar jet when making landfall. They can sometimes strengthen during and even just after landfall, which produces very strong sustained wind inland but with gusts only 15-20% above sustained wind.

This helps explain earlier posts regarding chasers being disappointed with Helene's wind.

[Steve]

Gonna vent for a minute. The damage inland is awful, widespread, maybe even historic, as is the impact of so many bridge and road washouts, so there is no need to exaggerate. But we have the usual Twitter drama queens declaring that a town is 'Gone', 'Wiped out', 'Wiped off the map', etc. From all the years watching reports from tornado 'storm chasers', 99% of the time when they claim this it turns out to be bogus. Similarly I have yet to find a town in the mountains that is actually 'gone'. There may be, there's probably a lot of info that hasn't gotten out yet (I'm afraid the death count will increase) but so far we're approaching 'Bodies in the trees!' hyperbole from some, followed by FWD;FWD;FWD;....

So here's hopefully a more balanced look at the terrible destruction we know about so far. Towns that Twits have declared 'Gone':

Black Mountain, NC, damage from massive flooding, possible landslides:

https://x.com/Wh_So_Serious/status/1840146821966115070

Montreat, NC:

https://x.com/dyllan_bwell/status/1839894472932446361

Montreat College is still there, most dorms are fine and a dining hall is open:

https://www.montreat.edu/2024/09/update-on-tropical-storm-helene-impact/?fbclid=IwZXh0bgNhZW0CMTEAAR0kT9KTfHr1Yj_rGmMX841D5hdbFWrZmhY277Y5Ppg6EPHwbF0bG7OCBaE_aem_4W5oYM-r2jJ02YvKz-W6Zg

And while that repost of what a "Black Mountain police chief" alleged said could end up being legitimate, I can find no independent verification of any of it by a news organization, and all the tweets seem to trace back to a college student that is a weather enthusiast. So I won't link it here.

Chimney Rock, NC, some of the river side business are gone, bridges and roads washed out:

https://x.com/Notizia18894/status/1840062674073190498

https://www.youtube.com/watch?v=coDkfDBNhg8

In a different vein, a couple that just avoided a landslide while driving reacts (#ChampagneSupernova):

https://x.com/wibw/status/1840134640012534244

Hey Freeze. Black Mountain is one of my favorite places ever. I have a sticker on my car of a bear from the great coffee shop in the city. What did the chief say? Also yeah, that is terrible.

[psyclone]

9 deaths confirmed in pinellas county and it sounds surge related. Our coast is reeling from surge damage but I had no idea or expectation of such a human toll.

[Sciencerocks]

 https://x.com/WXFatalities/status/1840202050640195729

[JaxGator]

Well, I’m back from no-service land (Valdosta) to report that I am safe and sound. Wow, that was a wild night. The eyewall of Hurricane Helene arrived in between 12:30-1am as a strong Category 2 with 110mph, with Category 3 gusts. Damage looks like it came from winds like that. Trees and power lines are down everywhere. Traffic lights are also damaged and destroyed. Reports of trees on houses and windows blown in by the winds. Thankful and blessed that my apartment has minor damage, and my car is undamaged. Power is still out and looks to be out till next Saturday, October 5th. Good news is that I have service now and can communicate with the outside world. I’m not sure Florida or Georgia will experience another hurricane this season (I pray not). However, this looks to be the hurricane of the season. It only takes one.

[Steve]

Well, I’m back from no-service land (Valdosta) to report that I am safe and sound. Wow, that was a wild night. The eyewall of Hurricane Helene arrived in between 12:30-1am as a strong Category 2 with 110mph, with Category 3 gusts. Damage looks like it came from winds like that. Trees and power lines are down everywhere. Traffic lights are also damaged and destroyed. Reports of trees on houses and windows blown in by the winds. Thankful and blessed that my apartment has minor damage, and my car is undamaged. Power is still out and looks to be out till next Saturday, October 5th. Good news is that I have service now and can communicate with the outside world. I’m not sure Florida or Georgia will experience another hurricane this season (I pray not). However, this looks to be the hurricane of the season. It only takes one.

Glad to hear you’re good Jax. When you get power and see all that happened, check out west NC. Boone, Asheville, I-40, Newton TN, Black Mountain. Crazy stuff that most of us probably wont see again. Lots of bad across Florida and GA. Different effects but bad where that inland rain came down. Damns failing (some survived) and rivers rolling through cities. Reminds me of Missouri back in like 1993 and Baton Rouge and east 2016. Can’t stop water.

[ljmac75]

We plotted the max sustained wind and gusts for Helene and the results were similar to Idalia and Francine (and 2002's Lily, 2020's Zeta). There were no reports of sustained hurricane force wind (1 min avg) inland across Florida or Georgia. However, there were plenty of reports of 95-110 mph gusts all the way up to the SC border along its track. Inland, the experience was of a strong tropical storm with Cat 2-3 wind gusts. So, what happened?

Clearly, the plane found very strong wind aloft, and maybe there were Cat 4 winds at the surface at some point offshore. However, Lily, Zeta, Idalia, Francine and Helene encountered a SW-NE jet as they approached the coast. Initially, the jet enhanced outflow and helped each storm to strengthen offshore. What aids strengthening eventually becomes detrimental wind shear. In each of these storms, the surface wind became decoupled from the stronger wind aloft. The effect was to lower the sustained surface wind but allow those stronger winds aloft to dip down. Wind gusts were nearly twice the sustained surface wind. Double the wind, four times the wind force. It doesn't take a 1-min average 100-120 mph wind to cause damage, a 10-20 second gust will produce a similar result.

Next time, keep a close eye on the predicted wind aloft as a storm nears landfall. If it's going to be encountering a jet, particularly later in the season, watch for this effect. Early season storms usually don't have to contend with the Polar jet when making landfall. They can sometimes strengthen during and even just after landfall, which produces very strong sustained wind inland but with gusts only 15-20% above sustained wind.

Good points about the jet leading to a higher-than-normal gust factor for storms undergoing trough interaction. However, the bolded section is incorrect, as Valdosta Regional Airport recorded a 102 mph sustained wind and a 133 mph gust (before it then failed). This also doesn't account for the sheer devastation in places like Keaton Beach, for example, where the tree and structural damage is pretty consistent with Category 4 landfalls of years past.

There was also dropsonde, radar velocity, and TDR data all indicating that 120-125kt was the appropriate intensity at landfall anyway.

I haven't been able to find the source of that 102 mph sustained and 133 mph gust mentioned. I've seen a tweet of it, but they didn't include any information about the station. I did see a personal weather station in the area that reported winds of up to 105 mph, but it didn't specify the period (1 second or 3 second gust, 1 minute sustained wind etc).

[mpic]

Gonna vent for a minute. The damage inland is awful, widespread, maybe even historic, as is the impact of so many bridge and road washouts, so there is no need to exaggerate. But we have the usual Twitter drama queens declaring that a town is 'Gone', 'Wiped out', 'Wiped off the map', etc. From all the years watching reports from tornado 'storm chasers', 99% of the time when they claim this it turns out to be bogus. Similarly I have yet to find a town in the mountains that is actually 'gone'. There may be, there's probably a lot of info that hasn't gotten out yet (I'm afraid the death count will increase) but so far we're approaching 'Bodies in the trees!' hyperbole from some, followed by FWD;FWD;FWD;....

So here's hopefully a more balanced look at the terrible destruction we know about so far. Towns that Twits have declared 'Gone':

Black Mountain, NC, damage from massive flooding, possible landslides:

https://x.com/Wh_So_Serious/status/1840146821966115070

Montreat, NC:

https://x.com/dyllan_bwell/status/1839894472932446361

Montreat College is still there, most dorms are fine and a dining hall is open:

https://www.montreat.edu/2024/09/update-on-tropical-storm-helene-impact/?fbclid=IwZXh0bgNhZW0CMTEAAR0kT9KTfHr1Yj_rGmMX841D5hdbFWrZmhY277Y5Ppg6EPHwbF0bG7OCBaE_aem_4W5oYM-r2jJ02YvKz-W6Zg

And while that repost of what a "Black Mountain police chief" alleged said could end up being legitimate, I can find no independent verification of any of it by a news organization, and all the tweets seem to trace back to a college student that is a weather enthusiast. So I won't link it here.

Chimney Rock, NC, some of the river side business are gone, bridges and roads washed out:

https://x.com/Notizia18894/status/1840062674073190498

https://www.youtube.com/watch?v=coDkfDBNhg8

In a different vein, a couple that just avoided a landslide while driving reacts (#ChampagneSupernova):

https://x.com/wibw/status/1840134640012534244

Anything concrete about Asheville would be highly appreciated.

[CrazyC83]

We plotted the max sustained wind and gusts for Helene and the results were similar to Idalia and Francine (and 2002's Lily, 2020's Zeta). There were no reports of sustained hurricane force wind (1 min avg) inland across Florida or Georgia. However, there were plenty of reports of 95-110 mph gusts all the way up to the SC border along its track. Inland, the experience was of a strong tropical storm with Cat 2-3 wind gusts. So, what happened?

Clearly, the plane found very strong wind aloft, and maybe there were Cat 4 winds at the surface at some point offshore. However, Lily, Zeta, Idalia, Francine and Helene encountered a SW-NE jet as they approached the coast. Initially, the jet enhanced outflow and helped each storm to strengthen offshore. What aids strengthening eventually becomes detrimental wind shear. In each of these storms, the surface wind became decoupled from the stronger wind aloft. The effect was to lower the sustained surface wind but allow those stronger winds aloft to dip down. Wind gusts were nearly twice the sustained surface wind. Double the wind, four times the wind force. It doesn't take a 1-min average 100-120 mph wind to cause damage, a 10-20 second gust will produce a similar result.

Next time, keep a close eye on the predicted wind aloft as a storm nears landfall. If it's going to be encountering a jet, particularly later in the season, watch for this effect. Early season storms usually don't have to contend with the Polar jet when making landfall. They can sometimes strengthen during and even just after landfall, which produces very strong sustained wind inland but with gusts only 15-20% above sustained wind.

Good points about the jet leading to a higher-than-normal gust factor for storms undergoing trough interaction. However, the bolded section is incorrect, as Valdosta Regional Airport recorded a 102 mph sustained wind and a 133 mph gust (before it then failed). This also doesn't account for the sheer devastation in places like Keaton Beach, for example, where the tree and structural damage is pretty consistent with Category 4 landfalls of years past.

There was also dropsonde, radar velocity, and TDR data all indicating that 120-125kt was the appropriate intensity at landfall anyway.

I haven't been able to find the source of that 102 mph sustained and 133 mph gust mentioned. I've seen a tweet of it, but they didn't include any information about the station. I did see a personal weather station in the area that reported winds of up to 105 mph, but it didn't specify the period (1 second or 3 second gust, 1 minute sustained wind etc).

 https://twitter.com/Local3News/status/1839528464044433915




I'm asking NWS Tallahassee about it as well.

[CrazyC83]

Here is how I would assess the BT of Helene (this is unofficial).

AL092024, HELENE, 20,
20240923, 1200, , LO, 17.2N, 81.8W, 25, 1006,
20240923, 1800, , LO, 17.9N, 81.9W, 30, 1004,
20230924, 0000, , TD, 18.2N, 82.2W, 30, 1003,
20230924, 0600, , TS, 18.6N, 82.7W, 35, 1001,
20240924, 1200, , TS, 19.0N, 83.6W, 40, 1000,
20240924, 1800, , TS, 19.4N, 84.6W, 45, 996,
20230925, 0000, , TS, 19.7N, 85.2W, 55, 990,
20230925, 0600, , TS, 20.3N, 85.9W, 60, 985,
20240925, 1200, , HU, 21.1N, 86.2W, 70, 979,
20240925, 1800, , HU, 22.0N, 86.6W, 75, 976,
20230926, 0000, , HU, 22.8N, 86.6W, 75, 973,
20230926, 0600, , HU, 23.6N, 86.4W, 80, 969,
20240926, 1200, , HU, 24.7N, 85.9W, 90, 963,
20240926, 1800, , HU, 26.7N, 84.9W, 105, 955,
20230927, 0000, , HU, 28.7N, 84.3W, 120, 941,
20230927, 0300, L, HU, 30.0N, 83.9W, 125, 938,
20230927, 0600, , HU, 31.3N, 83.4W, 80, 957,
20240927, 1200, , TS, 34.4N, 83.0W, 50, 970,
20240927, 1800, , EX, 36.7N, 84.7W, 35, 982,
20240928, 0000, , EX, 37.9N, 87.5W, 30, 986,

* Genesis is moved up 12 hours to 0000Z September 24. The recon flight around 1800Z on September 23 did not find a conclusive center, however, a weak center was identified around 0300Z September 24 in the night flight and Dvorak was up to T2.0. Given later trends, it was probably enough to call it a tropical depression at that time (and a tropical storm at 0600Z).
* The over-water intensities and the track are largely smoothed out. Most changes are within +/- 0.2 degrees, 5 knots or 2-3 millibars.
* It is clear that it rapidly intensified right up to landfall. The highest flight-level winds were 136 kt with the NOAA plane, which is about 120 kt at the surface before it left at about 0100Z, while the AF plane maxed out at about 132 kt just before landfall (supporting 119 kt). Radar velocities, however, were somewhat stronger, supporting as high as 130 kt, while satellite signatures (T6.5-7.0) supported at least 125 kt. It is also possible the recon missed the strongest winds as they may have been so close to shore. The SFMR should be ignored due to shoaling. Additionally, the pressure fell a bit more after the NOAA plane left. Based on all that, I estimate the landfall intensity was 125 kt. Consideration was made for 130 kt, but perhaps the radar data was too transitory. The 938 mb pressure is maintained based on the last Recon flight and surface data inland with pressures in Perry around 943 mb.
* Helene carried hurricane force winds well inland, deep into Georgia and possibly into South Carolina. That said, the latter state is too inconclusive to consider a hurricane impact - I would go with AFL4 (NW Florida) and IGA2 (inland Georgia).
* Extratropical transition is set at 1800Z, although it may have happened a bit sooner.

I haven't seen any new data to really change these thoughts. Regardless of the validity of that 102 mph reading (I'm suspicious of it since that would have to perfectly capture the maximum winds), I think all these are reasonable. We'll see once the NWS PSR's come out in the coming days and weeks.

[Zarniwoop]

We plotted the max sustained wind and gusts for Helene and the results were similar to Idalia and Francine (and 2002's Lily, 2020's Zeta). There were no reports of sustained hurricane force wind (1 min avg) inland across Florida or Georgia. However, there were plenty of reports of 95-110 mph gusts all the way up to the SC border along its track. Inland, the experience was of a strong tropical storm with Cat 2-3 wind gusts. So, what happened?

Clearly, the plane found very strong wind aloft, and maybe there were Cat 4 winds at the surface at some point offshore. However, Lily, Zeta, Idalia, Francine and Helene encountered a SW-NE jet as they approached the coast. Initially, the jet enhanced outflow and helped each storm to strengthen offshore. What aids strengthening eventually becomes detrimental wind shear. In each of these storms, the surface wind became decoupled from the stronger wind aloft. The effect was to lower the sustained surface wind but allow those stronger winds aloft to dip down. Wind gusts were nearly twice the sustained surface wind. Double the wind, four times the wind force. It doesn't take a 1-min average 100-120 mph wind to cause damage, a 10-20 second gust will produce a similar result.

Next time, keep a close eye on the predicted wind aloft as a storm nears landfall. If it's going to be encountering a jet, particularly later in the season, watch for this effect. Early season storms usually don't have to contend with the Polar jet when making landfall. They can sometimes strengthen during and even just after landfall, which produces very strong sustained wind inland but with gusts only 15-20% above sustained wind.

Thank you for this post.

[Teban54]

NHC forecast for Harvey 60 hours before landfall:

INIT 23/1500Z 21.5N 92.5W 30 KT 35 MPH
12H 24/0000Z 22.3N 93.2W 35 KT 40 MPH
24H 24/1200Z 23.8N 93.9W 40 KT 45 MPH
36H 25/0000Z 25.2N 94.9W 50 KT 60 MPH
48H 25/1200Z 26.7N 96.3W 60 KT 70 MPH
72H 26/1200Z 29.0N 97.3W 40 KT 45 MPH...INLAND
96H 27/1200Z 29.8N 96.9W 35 KT 40 MPH...INLAND
120H 28/1200Z 30.0N 95.0W 35 KT 40 MPH...INLAND

NHC forecast for Michael 80 hours before landfall:

INIT 07/0900Z 18.6N 86.9W 30 KT 35 MPH
12H 07/1800Z 19.4N 86.7W 35 KT 40 MPH
24H 08/0600Z 20.8N 86.4W 45 KT 50 MPH
36H 08/1800Z 22.3N 86.6W 50 KT 60 MPH
48H 09/0600Z 23.9N 87.1W 55 KT 65 MPH
72H 10/0600Z 27.6N 87.3W 65 KT 75 MPH
96H 11/0600Z 32.0N 84.0W 45 KT 50 MPH...INLAND
120H 12/0600Z 37.0N 76.0W 45 KT 50 MPH...NEAR THE VA COAST

NHC forecast for Laura 75 hours before landfall:

INIT 24/0300Z 20.1N 76.6W 55 KT 65 MPH...NEAR CUBA
12H 24/1200Z 21.1N 79.4W 55 KT 65 MPH...NEAR CUBA
24H 25/0000Z 22.5N 82.6W 60 KT 70 MPH...NEAR CUBA
36H 25/1200Z 23.8N 85.7W 65 KT 75 MPH
48H 26/0000Z 25.3N 88.5W 70 KT 80 MPH
60H 26/1200Z 27.1N 90.9W 80 KT 90 MPH
72H 27/0000Z 29.2N 92.4W 90 KT 105 MPH...NEAR THE COAST
96H 28/0000Z 34.2N 90.9W 40 KT 45 MPH...INLAND
120H 29/0000Z 37.4N 83.7W 25 KT 30 MPH...POST-TROP/REMNT LOW

NHC forecast for Ida 73 hours before landfall:

INIT 26/1500Z 16.9N 79.2W 30 KT 35 MPH
12H 27/0000Z 18.2N 80.4W 35 KT 40 MPH
24H 27/1200Z 20.3N 82.0W 45 KT 50 MPH
36H 28/0000Z 22.5N 83.9W 55 KT 65 MPH...INLAND
48H 28/1200Z 24.4N 86.0W 65 KT 75 MPH...OVER WATER
60H 29/0000Z 26.1N 88.1W 80 KT 90 MPH
72H 29/1200Z 27.7N 90.0W 95 KT 110 MPH
96H 30/1200Z 30.5N 92.0W 70 KT 80 MPH...INLAND
120H 31/1200Z 33.7N 91.2W 30 KT 35 MPH...INLAND

NHC forecast for Ian 76 hours before landfall:

INIT 25/1500Z 15.2N 79.8W 45 KT 50 MPH
12H 26/0000Z 16.5N 81.1W 55 KT 65 MPH
24H 26/1200Z 18.1N 82.5W 70 KT 80 MPH
36H 27/0000Z 20.1N 83.7W 90 KT 105 MPH
48H 27/1200Z 22.0N 84.4W 105 KT 120 MPH
60H 28/0000Z 23.9N 84.8W 115 KT 130 MPH
72H 28/1200Z 25.5N 84.8W 115 KT 130 MPH
96H 29/1200Z 28.0N 84.4W 95 KT 110 MPH
120H 30/1200Z 30.3N 83.7W 65 KT 75 MPH...INLAND

NHC forecast for Idalia 80 hours before landfall:

INIT 27/0300Z 21.1N 86.4W 30 KT 35 MPH
12H 27/1200Z 20.9N 86.4W 35 KT 40 MPH
24H 28/0000Z 20.9N 86.2W 40 KT 45 MPH
36H 28/1200Z 21.6N 85.9W 45 KT 50 MPH
48H 29/0000Z 23.1N 85.7W 55 KT 65 MPH
60H 29/1200Z 25.0N 85.5W 65 KT 75 MPH
72H 30/0000Z 27.5N 84.8W 70 KT 80 MPH
96H 31/0000Z 32.7N 81.5W 45 KT 50 MPH...INLAND
120H 01/0000Z 35.2N 76.7W 35 KT 40 MPH...INLAND

And, while not in the Gulf, NHC forecast for Otis just 27 hours before landfall:

INIT 24/0300Z 13.6N 97.9W 45 KT 50 MPH
12H 24/1200Z 14.4N 98.3W 50 KT 60 MPH
24H 25/0000Z 15.5N 98.9W 55 KT 65 MPH
36H 25/1200Z 16.4N 99.5W 60 KT 70 MPH
48H 26/0000Z 17.3N 100.3W 50 KT 60 MPH...INLAND
60H 26/1200Z 18.0N 101.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 27/0000Z...DISSIPATED

(Original comment here)

NHC forecast for Helene 84 hours before landfall:

INIT 23/1500Z 17.6N 82.0W 25 KT 30 MPH...POTENTIAL TROP CYCLONE
12H 24/0000Z 18.6N 82.4W 30 KT 35 MPH...TROPICAL CYCLONE
24H 24/1200Z 19.5N 83.7W 40 KT 45 MPH
36H 25/0000Z 20.6N 85.1W 50 KT 60 MPH
48H 25/1200Z 22.1N 86.0W 65 KT 75 MPH
60H 26/0000Z 24.2N 86.0W 85 KT 100 MPH
72H 26/1200Z 27.1N 85.1W 95 KT 110 MPH
96H 27/1200Z 34.0N 83.0W 35 KT 40 MPH...INLAND
120H 28/1200Z 38.5N 87.0W 20 KT 25 MPH...POST-TROPICAL

[caneman]

What else is amazing is that, from tropical cyclogenesis to loss of characteristics was barely 3 1/2 days. Yet in that time it charged up to a category 4 and did historic damage.

This is a great point and illustrates the gulf is a powder keg at peak season. I'd suggest any spot on the US gulf coast is vulnerable to an extreme hurricane because the sea is insanely warm. Let's dispatch of this antiquated idea that certain stretches are exempt because of climo. Our record is simply not long enough. Every spot has a return frequency given a sufficient timeline (which we lack hence Tampa Bay's absurdly low record surge value). To the extent hurricane seasons seem to be increasingly back loaded...if anything hurricane strike frequency in the central and eastern gulf may increase over time. I'm definitely staying on high ground

100%. I don't why people refer to climatology so much. We don't have a long enough history for sampling and to make even an assumption that's better than 50/50. Heck, the last hurricane that was this bad for Tampa Bay was likely 1921 I believe. Our surge was set at 5 - 8 ft. This time. It darn near surpassed that. I saw people in zone B darn near get flooded. I would assume and hope that in the future, our surge value predictions would have to go even higher. For example, knowing what we know now, our surge prediction should have been up to 10 ft. Another pet peeve I have is when people say why are they so close to the water, why don't they have better construction etc... My home was built in 1968 but others even older. Many things changed during that time including more people, better construction, gained experience, better engineering, architecture and more.......

[caneman]

We plotted the max sustained wind and gusts for Helene and the results were similar to Idalia and Francine (and 2002's Lily, 2020's Zeta). There were no reports of sustained hurricane force wind (1 min avg) inland across Florida or Georgia. However, there were plenty of reports of 95-110 mph gusts all the way up to the SC border along its track. Inland, the experience was of a strong tropical storm with Cat 2-3 wind gusts. So, what happened?

Clearly, the plane found very strong wind aloft, and maybe there were Cat 4 winds at the surface at some point offshore. However, Lily, Zeta, Idalia, Francine and Helene encountered a SW-NE jet as they approached the coast. Initially, the jet enhanced outflow and helped each storm to strengthen offshore. What aids strengthening eventually becomes detrimental wind shear. In each of these storms, the surface wind became decoupled from the stronger wind aloft. The effect was to lower the sustained surface wind but allow those stronger winds aloft to dip down. Wind gusts were nearly twice the sustained surface wind. Double the wind, four times the wind force. It doesn't take a 1-min average 100-120 mph wind to cause damage, a 10-20 second gust will produce a similar result.

Next time, keep a close eye on the predicted wind aloft as a storm nears landfall. If it's going to be encountering a jet, particularly later in the season, watch for this effect. Early season storms usually don't have to contend with the Polar jet when making landfall. They can sometimes strengthen during and even just after landfall, which produces very strong sustained wind inland but with gusts only 15-20% above sustained wind.

Thank you for this post.

Great post wxman57. I can however tell you that far to much emphasis is put on wind and not water. Maybe there also needs to be a Category rating for surge events and or flooding risks due to rain?. People seem to pay more attention when you say category. For example, Helene could have been rated perhaps as a Cat. 4 surge event or something like that. Either way, we somehow need to put equal emphasis on water as we do wind. I've noticed that people get far more caught on wind than water.

[blueskies]

Pinellas county so far has 2 storm surge deaths. The other 3 are yet to be determine. Death toll could grow

Really unfortunate, they had days of warning too.

The problem is no one alive here has ever even seen that type of storm surge. Any storm surge warning previously were never that high and never ever went close to max high predicted. Even me as a tracker of 25 years am left stunned at the surge we got. Going forward, the experience will create wisdom

I think that the storm surge predictions for the Pinellas coast and Tampa Bay prior to Idalia last year were quite high, but did not end up reaching predicted heights or levels of damage.

Based on that, many people here thought that their properties could withstand Idalia surge prediction heights.

[blueskies]

What else is amazing is that, from tropical cyclogenesis to loss of characteristics was barely 3 1/2 days. Yet in that time it charged up to a category 4 and did historic damage.

This is a great point and illustrates the gulf is a powder keg at peak season. I'd suggest any spot on the US gulf coast is vulnerable to an extreme hurricane because the sea is insanely warm. Let's dispatch of this antiquated idea that certain stretches are exempt because of climo. Our record is simply not long enough. Every spot has a return frequency given a sufficient timeline (which we lack hence Tampa Bay's absurdly low record surge value). To the extent hurricane seasons seem to be increasingly back loaded...if anything hurricane strike frequency in the central and eastern gulf may increase over time. I'm definitely staying on high ground

100%. I don't why people refer to climatology so much. We don't have a long enough history for sampling and to make even an assumption that's better than 50/50. Heck, the last hurricane that was this bad for Tampa Bay was likely 1921 I believe. Our surge was set at 5 - 8 ft. This time. It darn near surpassed that. I saw people in zone B darn near get flooded. I would assume and hope that in the future, our surge value predictions would have to go even higher. For example, knowing what we know now, our surge prediction should have been up to 10 ft. Another pet peeve I have is when people say why are they so close to the water, why don't they have better construction etc... My home was built in 1968 but others even older. Many things changed during that time including more people, better construction, gained experience, better engineering, architecture and more.......

I think that Waxman57 said that storm surge for Tampa Bay area could be higher than predicted for this storm.

[SecondBreakfast]

Anyone with Cajun navy contacts in NC? Friend of mine is frantic to find her parents in the Sherwood Forest neighborhood of Cedar Mt, NC. Landslides were reported near their home. I knew there was a number around a few years back.

There is a facebook page for the United Cajun Navy Carolinas.

You could try contacting Cajun Navy 2016 / Pinnacle SAR at pinnaclesar.org or (833) 225-8616. Maybe they have contact information for the Carolinas.

There appear to be various organizations now using the term "cajun army" in their name.

Thank you so much. She was able to get word they were okay and have food and water but it is so so bad. This is a family that moved north after losing everything to Wilma, it’s really not fair. I’m heartbroken.

[caneman]

This is a great point and illustrates the gulf is a powder keg at peak season. I'd suggest any spot on the US gulf coast is vulnerable to an extreme hurricane because the sea is insanely warm. Let's dispatch of this antiquated idea that certain stretches are exempt because of climo. Our record is simply not long enough. Every spot has a return frequency given a sufficient timeline (which we lack hence Tampa Bay's absurdly low record surge value). To the extent hurricane seasons seem to be increasingly back loaded...if anything hurricane strike frequency in the central and eastern gulf may increase over time. I'm definitely staying on high ground

100%. I don't why people refer to climatology so much. We don't have a long enough history for sampling and to make even an assumption that's better than 50/50. Heck, the last hurricane that was this bad for Tampa Bay was likely 1921 I believe. Our surge was set at 5 - 8 ft. This time. It darn near surpassed that. I saw people in zone B darn near get flooded. I would assume and hope that in the future, our surge value predictions would have to go even higher. For example, knowing what we know now, our surge prediction should have been up to 10 ft. Another pet peeve I have is when people say why are they so close to the water, why don't they have better construction etc... My home was built in 1968 but others even older. Many things changed during that time including more people, better construction, gained experience, better engineering, architecture and more.......

I think that Wxman57 said that storm surge for Tampa Bay area could be higher than predicted for this storm.

He did. I asked him and he said expect 10 foot. Going forward, our surge predictions need to be higher than what the warnings was for. Warning were 5 to 8 and should have been 10 ft. Max