(9/23/24, 2 pm) PTC 9 to become Helene, heavy rain and wind may impact Western Carolinas Thursday Night-Friday

Good Monday afternoon to everyone,

We continue to monitor the latest on an organizing tropical system in the Northwest Caribbean that will move northwest into the Gulf of Mexico over the next 48 hours. The National Hurricane Center began advisories on Potential Tropical Cyclone Nine at 11 am this morning, below is the first NHC forecast track.


A look at the system this morning shows a disorganized area of convection to the right of a mid-level center between Jamaica and the Yucatan. All guidance shows this moving to the northwest, through the Yucatan Channel and then coming together to form “Helene” by tomorrrow.


From a forecasters standpoint, the synoptics is pretty straight-forward with future Helene as an upper low will cut off across the Ozarks and work down the Lower Mississippi River Valley. Meanwhile a ridge off the Southeast US coastline will remain in place. These two features working together will help slingshot the storm northward with a landfall expected near the Florida Big Bend Region by Thursday. The exact landfall will ultimately be based on where a low level circulation can form with the developing storm. Once that occurs, that information will go into the computer models and should help iron out those details.


The blend of ensembles seems to be lining up well with everything we mentioned above. The spread in guidance is as much related to the lack of consistency in initialization points.


The current NHC track along with all guidance suggests that a flood threat will exist across Western North Carolina beginning Thursday night and increasing on Friday as the center of Helene may track right over or just west of the Blue Ridge escarpment. That will help provide a deep and prolonged southeast flow to the entire region. Given the rains from last week and the potential for showers early this week, the ground may be fairly saturated prior to the expected arrival of heavy rains associated with this upcoming storm.

Some very heavy rainfall amounts may occur in our upslope regions. We are not ready to commit to a forecasted amount but the National Blend of Models (posted below) shows widespread 4-8 inch amounts with higher in those favored upslope areas. That could result in some significant flash flooding, river flooding and mudslides should it verify.


The other concern with Soon-to-be Helene is the potential that we may be dealing with a major hurricane accelerating inland at landfall. All guidance is suggesting that come gusty winds could push into the Western Carolinas as it approaches Friday morning. The GFS in particular is showing 70 mph wind gusts in Upstate South Carolina with some 50 mph gusts along the I-40 Corridor in WNC.

If there’s any aspect of the storm that has most uncertainty it is with the inland wind impacts.


The Bottom Line…

If you are anywhere across Western North Carolina, I would prepare for excessive rainfall for Thursday and Friday. Those located along rivers and streams should make plans for leaving when necessary. Also, those in more urban settings, make sure and clean up any clogged drains or ditches from fallen leaves or dead grass, so water can drain efficiently.

We also suggest that you prepare for wind gusts on Friday that at the very least could down some trees and power lines. Again, this will be dependent on how strong PTC 9 becomes at landfall.

Our weather team will continue to monitor this situation, a new blog on this storm will be posted on Tuesday as more guidance rolls in.


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