Hurricane Helene: Extreme flooding in western North Carolina

SAVANNAH, Ga. (WSAV) – Hurricane Helene was a historic storm that will be on the minds of those affected for years to come. During the evening of Sept. 26, the storm made landfall along Florida’s Big Bend area as a category 4 with wind speeds of 140 mph.

The storm brought a wide range of impacts from hurricane-force wind gusts which knocked down trees and wiped out power, to storm surge flooding and even tornadoes. Some of the states most impacted were Florida, Georgia, Tennessee, South Carolina and North Carolina.

Another impact of the storm is extreme inland flooding due to rainfall in the Appalachian mountains in western North Carolina and parts of eastern Tennessee. With each passing day, we are learning that this part of the storm will go down in history as being the most impactful to not only property but to human lives as well.

So how did this all happen?

Before Hurricane Helene moved into the region, a stalled boundary was set up which brought heavy rain to parts of the Southeast.

The heaviest of the rain fell in the mountains where the terrain provided extra lift and amplified the ongoing rainfall. This rain fell over a couple of days leading up to the storm adding up to over 6 inches in some locations in higher elevations.

As a result, the soil became saturated and runoff caused the water to flow into surrounding rivers and raise their levels.

Next, as Hurricane Helene made landfall and moved north, tropical downpours added to the rainfall that the region had already experienced. While tracking north through the Southeast, an upper-level system associated with the stalled boundary caused Helene to make a northwest turn right into parts of the southern Appalachians.

With this track, strong easterly winds on the east and northeast sides of the storm drove the core of Helene’s tropical airmass straight into mountainous terrain forcing the air to rise.

This is a process in meteorology we call “orographic lift.”

When a moist airmass, in this case, Helene, travels into mountainous areas, the terrain forces the air upward. As the air goes up it cools the air and condenses water molecules leading to cloud formation and amplified precipitation.

Since the ground across the area was already saturated due to a stalled front before Helene, the soil could not hold any more moisture. As tropical downpours amplified by the mountainous terrain moved through, the water levels in valleys, rivers and streams filled up turning these waterways into raging rapids.

When the rain ended and the clouds cleared, parts of the landscape were forever changed as over 20 inches of rain fell in some areas. Parts of major roadways like I-40 and I-26 have been completely shut down and may not be open again until 2025. Additionally, residents of these areas will have to deal with power outages for potentially months as this storm wiped out surrounding infrastructure.

For those who are willing and able to donate, visit this link to help those who were heavily impacted by Hurricane Helene.