NC Floods, CA Drought, and The Role of Randomness
October 22nd, 2024 by Roy W. Spencer, Ph. D.
The recent devastating floods in western North Carolina were not unprecedented, but were certainly rare. A recent masters thesis examining flood deposits in the banks of the French Broad River over the last 250-300 years found that a flood in 1769 produced water levels approximately as high as those reported in the recent flood from Hurricane Helene. So, yes, the flood was historic.
Like all severe weather events, a superposition of several contributing factors are necessary to make an event “severe”, such as those that led to the NC floods. In that case, a strong hurricane combined with steering currents that would carry the hurricane on a track that would produce a maximum amount of orographic uplift on the east side of the Smoky Mountains was necessary in order to produce the widespread 12-20 inch rainfall amounts, and the steering currents had to be so strong that the hurricane would penetrate far inland with little weakening.
Again, all severe weather events represent the somewhat random combining of amplifying components: In the case of Hurricane Helene, they produced the unlucky massive flooding result that the region had not seen in hundreds of years.
https://www.drroyspencer.com/2024/10/nc-floods-ca-drought-and-the-role-of-randomness/
