ATL: HELENE - Post-Tropical - Discussion

[gailwarning]

Quick question regarding storm surge. Does a faster storm mean stronger surge? I know the larger the hurricane, the higher the waves but does speed play a role as well? I imagine it probably does.

So the main three factors in storm surge are wind speed, fetch and duration. Fetch is the distance the winds blow, and duration is how long they blow. So a faster moving storm would have less duration than a slower moving storm, so less surge. However, this is a very large storm, so fetch is higher than usual.

Is topography of the sea floor near land also a factor? In a lot of places on the Gulf, you can walk out a long way without being over your head. On the FL Atlantic side, they don't get surge as severe because the ocean water gets deeper more quickly. True?

[Chemmers]

Duel hot towers rotating around the core again, unfortunately think it will intensify all the way to land fall in the next 6 hour stay safe everyone

[weeniepatrol]

[Pipelines182]

It’s been hours of wrapping convective bursts, and the eye has still not cleared. I’m doubtful it will; several hurricane model runs predicted this.

IIRC, Michael didn't really have a clear eye until just before landfall as a Cat 5.

It was ragged but cleared out maybe 12 hours before landfall? I think the symmetrical stadium eye showed up maybe 4 hours before landfall.

[Nimbus]

Calculations show me that Helene is now moving on a 19 deg heading during the past 5-6 hours, compared to 25 deg heading during the morning, it will have to start moving almost on a due north heading to track over Tallahassee.

Klystron 9 showing a slight eastern path than the NHC line but well within the Cone

For anyone interested, the eyewall is on Tampa Radar now

https://baynews9.com/fl/tampa/weather/radar

St Pete is starting to see some power outages over 10,000 without power in the Tampa Bay area now.
40 mph winds cause line slap but you would think with the eyewall that close it would be worse?

[Woofde]

That's a solid donut jesus...

[FLLurker32]

Calculations show me that Helene is now moving on a 19 deg heading during the past 5-6 hours, compared to 25 deg heading during the morning, it will have to start moving almost on a due north heading to track over Tallahassee.

I went back to look and couldn’t find any recent models that had such a sharp change in direction at this strength. Most have the change as a much more subtle curvature.

At the current size, strength and forward speed, is it even possible?

[Nuno]

I am starting to doubt. The wind is so unbearably hot its like a blow dryyer. Very unusual wind temperature

It's so weird. I am 5 minutes away from the Ruskin Radar and I spent some time outside and I felt out of air.

yes its very peculiar. does not feel like any hurricane ive ever felt.

The driest storm I've seen in a while. This has the feeling or vibe of a Wilma-type of event, with the speed that these bands are rolling through.

[FLpanhandle91]

[Grumpy]

Lido Key in Sarasota is under water. Siesta Key wiil be shortly,.

[Teban54]

https://i.imgur.com/9uda5rz.png

And to think this was already the case 1.5 hours ago. No wonder the MH upgrade around that time and the fast drop in pressure since then. If that eye is still persisting now, it also means low chances of a last-minute EWRC unlike Idalia did.

[Frank P]

You can see the eye tightening
https://i.imgur.com/QHzON8b.gif

Dang on that loop looks like it’s headed towards St George’s Island

[USTropics]

This storm is booking it, at 21 miles an hour to the NNE, according to the advisory.

Do major hurricanes usually travel that fast?

If so, this storm should be on land pretty soon.

You basically have an upper level speedway at 200mb (where the steering is now more dictating how Helene moves as she deepens). The combined steering influences from the cutoff low and upper-level ridging to the southeast of Helene ushers this quickly towards the NNE (there is also high pressure to the east at 500mb):

[Hurrilurker]

Recon is about 1.5 hours away, we might only get another 2 or maybe 3 samples before landfall?

[gailwarning]

Opal was worse than Irma...by far. The wind blew down trees literally all over midtown and downtown. I had to walk to work because it was so bad I could not drive and I was five mins away from the Bell South Tower (as it was known back then)

I am in Towns County, GA just about a mile from the NC border, far eastern part of the state. It has been raining heavily for the most part since early Wed. afternoon. There have already been outages affecting 4,500 customers (which is quite a few for up here). Doesn't bode well for the actual storm. Is there info available for how much rain has fallen so far? I'm no expert on tropical storms but have been hanging around here for quite a few years now. It's appalling how many up here think this is no big deal.

I'm in Midtown Atlanta and I've recorded just shy of 3 inches in my rain gauge since around 2pm.
Recon has made their decent to 10,000 feet. Wont be long now

I discovered that TVA measures rainfall at all of their dams, plus a few other locations. Hiawassee, the town next to mine, has had 3.5 inches yesterday and today so far. I'm not at risk for flooding as I live on a hill, but am a bit concerned about one tree. I've removed quite a few hazardous trees, but I just discovered recently this one has some rot at the base.

Best of luck to you and everybody in the path of this monster.

[BIFF_THE_UNRULY]

looks like this is the closest its gonna get to Tampa/St Pete

[CrazyC83]

Recon is about 1.5 hours away, we might only get another 2 or maybe 3 samples before landfall?

Another AF plane should arrive by 7 pm EDT, which should carry us to landfall.

[Texashawk]

Man, this sure is looking like a Tallahassee storm. I hope people took it seriously! Still time to get out, but after it gets dark..

[NDG]

70 mph wind gusts now in downtown St Pete.

Sep 26, 4:24 pm 85 78 80 97 SSE 44G70

[Anti-freeze]

Quick question regarding storm surge. Does a faster storm mean stronger surge? I know the larger the hurricane, the higher the waves but does speed play a role as well? I imagine it probably does.

So the main three factors in storm surge are wind speed, fetch and duration. Fetch is the distance the winds blow, and duration is how long they blow. So a faster moving storm would have less duration than a slower moving storm, so less surge. However, this is a very large storm, so fetch is higher than usual.

Good explanation.

But mandatory: