Major Hurricane Helene

[hawkeye_wx]

Recon is making one final pass through the center and it has found a solid nw wobble since the last pass.

[TPAwx]

Before perspective here in South Tampa.  We have 4 lanes and medians in between the pending surge and our hood.  Record known surge for Tampa is 10.5 ft from the 1921 hurricane, which was the last major to hit here.  Helene's current 5-8 surge forecast should not exceed that mark, but wouldn't be surprised to see the high end or a bit more.  Ironically the worst surge impact I've had IMBY since relocating here was from decaying TS ETA in Nov 2020.  Point is it doesn't take a major cane to drive surge or flooding here.  We regularly flood from PM summer storms.

[GaWx]

38 minutes ago, Allsnow said:

 

Atlanta’s record low SLP of 981 mb as well as records for much of the W half of GA will certainly be threatened and some if not many will probably be broken. Many current record lows in central GA E to Augusta are from the Storm of the Century of March of 1993.

 One correction: lowest recorded GA SLP (GA coast is much lower than 970.5) is way too high. It is in the 950s (1890s). But that’s irrelevant for Helene, of course.

[Radtechwxman]

13 minutes ago, hawkeye_wx said:

Recon is making one final pass through the center and it has found a solid nw wobble since the last pass.

Has the center passed the Yucatan or could this put it in position to interact with land? 

[cardinalland]

Deepening appears to have stagnated for the past couple hours. I imagine it has to do with the dry air intrusion that you can see on satellite and radar. Once that mixes out strengthening will resume...

[hawkeye_wx]

1 minute ago, Radtechwxman said:

Has the center passed the Yucatan or could this put it in position to interact with land? 

The center is now past the Yucatan.

[GaWx]

12Z UKMET shifted a little W vs 0Z run’s far NE GA and once again comes in stronger like typical UK trend:

TROPICAL STORM HELENE ANALYSED POSITION : 21.5N 86.2W

ATCF IDENTIFIER : AL092024

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 25.09.2024 0 21.5N 86.2W 984 51
0000UTC 26.09.2024 12 23.1N 86.3W 979 48
1200UTC 26.09.2024 24 25.5N 85.4W 975 50
0000UTC 27.09.2024 36 29.6N 83.9W 970 55
1200UTC 27.09.2024 48 35.6N 84.0W 984 31
0000UTC 28.09.2024 60 38.7N 86.8W 989 35
1200UTC 28.09.2024 72 36.9N 89.5W 996 16
0000UTC 29.09.2024 84 36.6N 89.3W 1003 12
1200UTC 29.09.2024 96 36.4N 89.3W 1006 10
0000UTC 30.09.2024 108 CEASED TRACKING

[hawkeye_wx]

The current recon plane's final pass found 978-979 mb.

[Radtechwxman]

4 minutes ago, hawkeye_wx said:

The current recon plane's final pass found 978-979 mb.

May stay steady state a bit while it tries to mix out that dry and reorganize its inner core

[weatherCCB]

12z hurricane models not backing down with rapid deepening tonight and tomorrow.  

 

 

[Wannabehippie]

6 minutes ago, Radtechwxman said:

May stay steady state a bit while it tries to mix out that dry and reorganize its inner core

Plus it is very close to the Yucatan, that has to be causing some issues with strengthening IMHO as an amateur.

[kayman]

https://x.com/wxbrad/status/1838943214671196303?t=KmRnhu4XHb-svVzxJ4WcbQ&s=19

Helene could be to Atlanta how wind damage like Hugo did to Charlotte

[Radtechwxman]

1 minute ago, Wannabehippie said:

Plus it is very close to the Yucatan, that has to be causing some issues with strengthening IMHO as an amateur.

Definitely could have impacted it some. Should see Helene really take off later today and tonight. 

[GaWx]

12Z Euro: even stronger vs the 960 of the 6Z with 954 landfall! tracks to just E of Macon and then to Athens

[andyhb]

New HWRF is, for lack of a better term, a complete disaster. Makes landfall as a very large/high end Cat 4, takes it over Tallahassee, and then remains sub-960 mb into N GA with gusts that would probably exceed 90 mph over a large area (along with the flooding in the Appalachians).

[beanskip]

2 minutes ago, GaWx said:

12Z Euro: even stronger vs the 960 of the 6Z with 954 landfall! tracks to just E of Macon and then to Athens

Any details on panhandle landfall location? 

[Radtechwxman]

1 minute ago, andyhb said:

New HWRF is, for lack of a better term, a complete disaster. Makes landfall as a very large/high end Cat 4, takes it over Tallahassee, and then remains sub-960 mb into N GA with gusts that would probably exceed 90 mph over a large area (along with the flooding in the Appalachians).

How likely do you think that is? I mean it does have Loop Current and great atmospheric conditions tonight. We saw what Ian did overnight even after crossing western Cuba. 

[GaWx]

5 minutes ago, andyhb said:

New HWRF is, for lack of a better term, a complete disaster. Makes landfall as a very large/high end Cat 4, takes it over Tallahassee, and then remains sub-960 mb into N GA with gusts that would probably exceed 90 mph over a large area (along with the flooding in the Appalachians).

Considering that the record low SLP for N GA is in the 970s, I’m assuming this is likely way overdone. I sure hope that’s the case. But you never know for sure as this is a very unique situation.

[WxWatcher007]

1 minute ago, beanskip said:

Any details on panhandle landfall location? 

GFS

 

Euro

[andyhb]

Just now, GaWx said:

Considering that the record low SLP for N GA is  in the 970s, I’m assuming this is likely way overdone. But you never know for sure.

Considering the storm makes landfall at sub 920 mb and is moving quite fast, this would be the worst case scenario for GA. Think Michael but larger.

[CoastalWx]

For Atlanta and Tallahassee it will really come down to track. NHC track is bad, but it would not shock me if we get some east ticks. So for Atlanta, if it moves east of the city, winds on the west side will be strong, but 40-55 vs 75+ is a huge difference. The inv trough that starts to set up after Helene makes landfall will help keep the LLJ on east side of the low. So we are talking massive differences in wind at both locations depending on track.

[LovintheWhiteFluff]

22 minutes ago, Wannabehippie said:

Plus it is very close to the Yucatan, that has to be causing some issues with strengthening IMHO as an amateur.

 

This area has cooler water due to more upwelling due to westerly winds. This is what I posted in the Beryl thread. The area extends a bit east of the peninsula and north of it. Throw in some dry air with this and you don't get a lot of deepening. 

 

The coastal area north of Yucatan has experienced a cooling SST trend from 1982 to 2015 during the upwelling season (May–September) that contrasts with the warming observed at the adjacent ocean area. Different drivers were analyzed to identify the possible causes of that unusual coastal cooling. Changes in coastal upwelling and in sea-atmosphere heat fluxes are not consistent with the observed coastal cooling. The eastward shift of the Yucatan Current observed over the last decades is hypothesized as the most probable cause of coastal cooling. This shift enhances the vertical transport of cold deeper water to the continental shelf from where it is pumped to the surface by upwelling favorable westerly winds.

 

https://www.sciencedirect.com/science/article/abs/pii/S0924796317303317#:~:text=The eastward shift of the,by upwelling favorable westerly winds.

[Seminole]

In 24 hours the forward speed of Helene is just ridiculous. I thought that systems that move this fast have a difficult time remaining vertically stacked?  

[Scott747]

All four of the hurricane models show a cat 4 landfall just s of Tallahassee with 3 of them putting it pretty much in the eyewall/eye, and considering the speed it will be moving of at least an upper end 3 if not still a 4.

[SnowGoose69]

3 minutes ago, CoastalWx said:

For Atlanta and Tallahassee it will really come down to track. NHC track is bad, but it would not shock me if we get some east ticks. So for Atlanta, if it moves east of the city, winds on the west side will be strong, but 40-55 vs 75+ is a huge difference. The inv trough that starts to set up after Helene makes landfall will help keep the LLJ on east side of the low. So we are talking massive differences in wind at both locations depending on track.

Direction is big too.  Due N-S winds are rare in ATL, the airport does not even have a N-S RWY much like DFW/DAL do not often see strong W-WSW winds so tree roots are likely not going to be able to handle 45-55 from 160-180 as well as they could 040-080.  60 plus forget it.  Georgia had real severe damage from Zeta despite winds being S-SW due to the fact the direction was rare.

[andyhb]

8 minutes ago, Radtechwxman said:

How likely do you think that is? I mean it does have Loop Current and great atmospheric conditions tonight. We saw what Ian did overnight even after crossing western Cuba. 

Would be dependent on it mixing out dry air and completing its inner core by tonight/early tomorrow.

[SnowGoose69]

The HWRF track is close to my thinking, although again if it comes in THAT strong I think it has more of an east of north component for a bit longer or at least more of one into S GA

[GaWx]

8 minutes ago, andyhb said:

Considering the storm makes landfall at sub 920 mb and is moving quite fast, this would be the worst case scenario for GA. Think Michael but larger.

 Yeah, I realize that the very large size and very high speed of movement are coming into play to unfortunately minimize how much the winds will come down/SLP rise by the time it gets to N GA (only ~9 hrs later) . I calculated an avg speed of ~28 mph from landfall to N GA, one of the fastest on record for a MH hitting the FL panhandle and moving N. (Eloise of 1975 was ~29). But my hope is that its 920 SLP is way overdone. With it being a very large storm, I’d think it would be difficult for it to get down to 920. Wouldn’t 940 mb be more reasonable considering its size and somewhat limited amount of time before landfall? Also, it temporarily has leveled off.

 If it is instead 940 mb, perhaps 20 mb could be added to the sub 960 prog for N GA and make it 970s though that would still be very bad and near records.

[Radtechwxman]

Curious what impact this dry air wrapping into circulation now will have on Helene. Can really see it eroding clouds on visible satellite wrapping into the COC. Could lower ceiling a bit if it takes a while to mix out. 

[purduewx80]

3 minutes ago, CoastalWx said:

For Atlanta and Tallahassee it will really come down to track. NHC track is bad, but it would not shock me if we get some east ticks. So for Atlanta, if it moves east of the city, winds on the west side will be strong, but 40-55 vs 75+ is a huge difference. The inv trough that starts to set up after Helene makes landfall will help keep the LLJ on east side of the low. So we are talking massive differences in wind at both locations depending on track.

Yeah, there is not a lot of model support for a track west of here like NHC has. Really hoping it tracks east since I have a full canopy of 150’ trees overhead.