Major Hurricane Helene

[Radtechwxman]

And there it is. Hurricane Helene. 80mph 979mb. Forecasting 125 mph landfall now. I think cat 4 is a decent if not good possibility. 

[NeonPeon]

Can someone clarify something for the uneducated.

The storm seems to have some dry air entrainment, but the general discussion has been that this was not likely to be an issue with this storm. Is what I'm seeing on satellite as dry air just subsidence from a storm that is lopsided, with an asymmetrical core? Are they one in the same?

[beanskip]

29 minutes ago, beanskip said:

So I know the NAM is pretty worthless for tropical systems, but it is, I think, noteworthy that it slowed down landfall by what looks like 6-8 hours on the 12z run vs. 6z. 

12Z ICON 2-3 hours slower as well.

Obviously, timing is a point of interest, but this is also more hours over warm Gulf waters. 

[schoeppeya]

3 minutes ago, NeonPeon said:

Can someone clarify something for the uneducated.

The storm seems to have some dry air entrainment, but the general discussion has been that this was not likely to be an issue with this storm. Is what I'm seeing on satellite as dry air just subsidence from a storm that is lopsided, with an asymmetrical core? Are they one in the same?

My guess is we are probably just seeing some structural changes and it may try and clear out an eye before the pressure starts falling again. Even when storms are going through RI we see periods where the pressure drops pause while the storms "consolidates" before the next wave of intensification. 

[BoulderWX]

10 minutes ago, Radtechwxman said:

And there it is. Hurricane Helene. 80mph 979mb. Forecasting 125 mph landfall now. I think cat 4 is a decent if not good possibility. 

Yup, horrible look for TLH with the center projected to pass just to the east. 

[NorthHillsWx]

As for dry air intrusion- this is totally normal for any developing hurricane. With the lack of shear at present, and the extremely vigorous convection the system is generating, I expect it to be easy to mix out as the core develops. This is a CLASSIC look of a storm primed to go. There is no inhibiting factor at present to prevent steady to rapid intensification. This is on schedule and to be honest that is a terrifying satellite look at this stage

[Windspeed]

[mention=9730]WxWatcher007[/mention] [mention=17109]NorthHillsWx[/mention] That dry slot you both were mentioning earlier seems to have been pulled into the developing core. Granted, I'm not sure how thorough the echoes are on the La Bajada radar, but perhaps this will help to keep Helene in check a bit longer until it can gain some separation away from the Yucatán landmass. Pretty much looking for anything to stunt or delay RI, which will make time an issue for Helene to reach MPI.

[RU848789]

Helene is obviously going to be devastating for the FL coast and just inland with high winds and surge and downed trees/power outages, but the untold story of this storm, when all is said and done, might be the torrential flooding, especially well inland in GA/AL/SC/TN/NC/VA/KY and particularly for the Apps.  

[StantonParkHoya]

Asheville going to be a mess

[Daniel Boone]

3 minutes ago, RU848789 said:

Helene is obviously going to be devastating for the FL coast and just inland with high winds and surge and downed trees/power outages, but the untold story of this storm, when all is said and done, might be the torrential flooding, especially well inland in GA/AL/SC/TN/NC/VA/KY and particularly for the Apps.  

That is through Monday.?. That is too low on Totals across Central/ ETN/SWVA . That looks more like a Total's Map through Friday for these area's. 

[Yanksfan]

3 minutes ago, StantonParkHoya said:

Asheville going to be a mess

My business manager is driving down there for a wedding in a couple of days.

[jm1220]

12 minutes ago, RU848789 said:

Helene is obviously going to be devastating for the FL coast and just inland with high winds and surge and downed trees/power outages, but the untold story of this storm, when all is said and done, might be the torrential flooding, especially well inland in GA/AL/SC/TN/NC/VA/KY and particularly for the Apps.  

Very often it seems these major Gulf storms have a “Part 2” somewhere that has huge flooding from heavy rain. This one looks likely to, Ida was over the NYC metro area, Camille was over VA, Opal was over GA etc. The preceding heavy rains inland this time will certainly make matters worse for the main event. Hopefully people inland are preparing. 

[Windspeed]

It is interesting to note that all of the prominent TC models simulated this dry slot instrusion off of the Yucatán landmass at this juncture, and all have the core mixing that out by this evening.

[AccuChris]

These zoomed in visible images are incredible to watch

https://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=mesoscale_01&x=685&y=1315&z=2&angle=0&im=60&ts=1&st=0&et=0&speed=130&motion=loop&maps%5Bborders%5D=white&maps%5Blat%5D=white&p%5B0%5D=band_02&opacity%5B0%5D=1&pause=20240925133125&slider=-1&hide_controls=1&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&draw_color=FFD700&draw_width=6


.

[lilj4425]

Tropical storm watch up for Upstate SC, midlands of SC (Columbia), Western NC, and all of northern/central Georgia. 

[Met1985]

26 minutes ago, StantonParkHoya said:

Asheville going to be a mess

Yeah all of WNC could have a lot of damage when all is said and done in this area.

[beanskip]

12z GFS stubbornly hanging on to a more easterly track -- landfall in Taylor County. This 50 miles would be huge for Tallahassee if it verified. Still wouldn't be a walk in the park given the size of the storm, but would spare the capital the most severe winds. Unfortunately GFS coups are few and far between ...

[WxWatcher007]

D1 High Risk (Flooding) added:

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1144 AM EDT Wed Sep 25 2024
Day 1
Valid 16Z Wed Sep 25 2024 - 12Z Thu Sep 26 2024

...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
NORTHEAST GEORGIA THROUGH FAR WESTERN SOUTH CAROLINA AND SOUTHWEST
NORTH CAROLINA...

..LIFE-THREATENING FLASH FLOODING INCREASINGLY LIKELY OVER THE
SOUTHERN APPALACHIANS..

Deep layer south to south-southwest flow will allow for the
advection of increasingly moist, unstable air to funnel poleward
ahead of Helene thanks to a closed upper low/trough centered over
the Mid-Mississippi Valley. Afternoon destabilization within the
budding warm sector along with sufficient left-exit region (LER)
jet dynamics from the trough will translate to more widespread
convective coverage across the Southeastern U.S into the
Central/Southern Appalachians as we move into the late-afternoon
and evening time frame. Areas across the Escarpment located over
far Northeast GA into the Western SC/NC border have seen 2" to as
much as 5" of rainfall in the last 24-36 hrs leading to a priming
of the top soil layer as indicated by the latest NASA SPoRT soil
moisture percentiles approaching 60-70% over the areas affected.
Recent CAMs and ensemble output have increased the QPF signal
across the Southeast with the axis of heaviest rainfall bisecting
Eastern AL up through Western GA into North GA and the Southern
Apps/Smokies bordering TN/SC/NC. HREF blended mean QPF indicates
widespread 3-6" of rainfall from this predecessor rainfall event
(PRE) that correlates with the strong upper forcing and deep
tropical connection to north of Helene as it wanders into the
Eastern Gulf. Probability fields are also very aggressive with the
signature for enhanced rainfall rates and totals with the EAS
signal for 3" settling at 50-80% within the Escarpment area into
Northeast GA. Neighborhood probabilities of >5" between 70-90+% and
>8" between 20-35% are more than sufficient for a very impactful
event expecting to unfold across the complex terrain in-of the
Southern Appalachians. Given the signals expressed via the hi-res
ensemble, along with ample support from the various ML output for
the heaviest rainfall, as well as coordination with the local
Greenville-Spartanburg WFO, a targeted High Risk was added for the
D1 period.

 

[SnowGoose69]

1 minute ago, beanskip said:

12z GFS stubbornly hanging on to a more easterly track -- landfall in Taylor County. This 50 miles would be huge for Tallahassee if it verified. Still wouldn't be a walk in the park given the size of the storm, but would spare the capital the most severe winds. Unfortunately GFS coups are few and far between ...

The meso models seem to be furthest west along with those hurricane models.  I still think a landfall point near where the NHC forecast is will be close but not sure the movement for awhile after landfall won't be more NNE of the current NHC track and mesos

[Jebman]

40 minutes ago, RU848789 said:

Helene is obviously going to be devastating for the FL coast and just inland with high winds and surge and downed trees/power outages, but the untold story of this storm, when all is said and done, might be the torrential flooding, especially well inland in GA/AL/SC/TN/NC/VA/KY and particularly for the Apps.  

How bad are things looking with respect to antecedent rainfall in the past ten days in those regions?

[buckeyefan1]

2 minutes ago, Jebman said:

How bad are things looking with respect to antecedent rainfall in the past ten days in those regions?

It’s not going to be pretty 

[nvck]

4 minutes ago, Jebman said:

How bad are things looking with respect to antecedent rainfall in the past ten days in those regions?

Up to 6 Inches over the past week in some of the mountains of NC (over past 7 days, but same idea)

[purduewx80]

4 minutes ago, Jebman said:

How bad are things looking with respect to antecedent rainfall in the past ten days in those regions?

Very noticeable drought here in Atlanta and most of the Apps. NC is still wet from PTC8. Soil moisture percentiles below. Not sure it will matter much, but at least it’s dry to start. 

[Met1985]

8 minutes ago, Jebman said:

How bad are things looking with respect to antecedent rainfall in the past ten days in those regions?

It won't matter here. Shits going to be unhinged if the forecasts are correct. 

[WxWatcher007]

8 minutes ago, SnowGoose69 said:

The meso models seem to be furthest west along with those hurricane models.  I still think a landfall point near where the NHC forecast is will be close but not sure the movement for awhile after landfall won't be more NNE of the current NHC track and mesos

Yeah, I think a middle ground is probably best and I’m kind of with you on that NNE motion. That may last a bit longer before a northward turn. 

For center impacts, every wobble “trend” is going to matter, especially considering that this one will be moving fast and may not have a chance to course correct. As the NHC said, 60nm is the 36hr average error. That’s significant. 

[Allsnow]

 

[CoastalWx]

22 minutes ago, purduewx80 said:

Very noticeable drought here in Atlanta and most of the Apps. NC is still wet from PTC8. Soil moisture percentiles below. Not sure it will matter much, but at least it’s dry to start. 

Andy! Didn't know you were in ATL now. Hope all is well, bud.

[Hotair]

Nice graphic showing recent impactful Florida storms and how Helene sits much more West presently at similar latitudes.  What is not yet clear is how the large wind field will compensate for this further West track in terms of overall impacts to the SW Florida coastline 

 

 

[BlizzardNole]

Real worried about Tallahassee.  The town is covered with tall pines and big oaks.  I was at FSU in Nov. 1985 when Kate made landfall as a weakening cat-2 (cat-1 by the time it went thru Tally) and it was a mess with big trees down everywhere and some people without power for days/weeks.  This thing looks scary

[jbenedet]

30 minutes ago, purduewx80 said:

Very noticeable drought here in Atlanta and most of the Apps. NC is still wet from PTC8. Soil moisture percentiles below. Not sure it will matter much, but at least it’s dry to start. 

Give it six hours.