By: Lead Forecaster Daniel Crawley
We continue a multi-part series looking back at Hurricane Helene, its evolution and how it turned into the largest natural disaster in the history of Western North Carolina replacing major weather events such as the floods of 1916 and 1940.
Between now and Saturday (Sept 27), the official 1-year anniversary, we will look back at the storm from a forecaster’s perspective here at Foothills Weather Network. We will go over the factors that created a three-day rain event that brought historic flooding to many river basins in WNC along with the impact of strong winds as Helene itself moved in. We will also re-live the post-storm impacts that Helene brought to the region, including several of the counties that we cover daily at Foothills Weather Network.
Part 4 of the series focuses on the events of September 25th, 2024 and the sense of urgency that kicked in for the weather community and for the general public on that day as the first impacts from this historic event take place.
With the start of the day, it was obvious that a major, if not historic weather event was getting ready to unfold over a period of three days. Helene was rapidly intensifying near the Yucatan Channel and was officially a hurricane at 11 am. Meanwhile a very-slow moving upper low was over the Ozarks developed a corridor of heavy precipitation on its eastern side and it was moving into Western North Carolina. That energy along with daytime heating helped create the Predecessor Rain Event (PRE) that hit the region late in the day.
Forecasters at both the local and national levels were closely monitoring the long-term impacts of Helene. The National Hurricane Center was one of the first to sound the alarm for major impacts of the storm post-landfall. In the 11 am forecast discussion, Helene was expected to undergo rapid intensification prior to landfall. NHC specially noted at 11 am how the strength and fast movement was going to result in rain/wind impacts well away from the coastline. The Southern Applachians was one area explicitly mentioned.
In coordination with national forecasters, the team of Meteorologists at the National Weather Service in Greenville-Spartanburg also upped its wording in regards to the impact of the PRE and Helene over multiple days.
Our forecast team was in-sync with other outlets in getting the word out and possessing a sense of urgency about the potential impacts. Our Chief Meteorologist Christopher White updated the blog that afternoon and with this update, a timeline of storm impacts and severity were stressed.
Being roughly hours away from the start, we started to shift from global computer models to more short range data to get a true visual look at how this will also come together.
As we have always said, the entire weather community strives in working together to send out a unified message to the public. That was our goal at Foothills Weather Network during this major event and that was to get the word out in a professional manner. The public took our word seriously.
By Wednesday afternoon as the PRE rain event was getting underway, several school systems in the Western Carolinas began adjusting after-school schedules or closing all-together as a precautionary measure. Local emergency management agencies went into protocol to begin notification of evacuations in areas prone to flash flooding.
The PRE-event rain kicked into high hear around 4 pm on the 25th and focused itself primarily along the Eastern Continental Divide which soaked portions of Polk, Rutherford, McDowell, Burke and Caldwell Counties with rainfall amounts in the 4-10 inch range with scattered amounts of rain further east. The end result was significant flash flooding along streams and creeks in those areas. Daytime heating and upper level winds helped focused the extremely heavy rainfall amounts. Once we got to the morning of the 26th, rain had took over the entire coverage area in a light-to-moderate fashion.
In the end, the PRE rain event unfortunately verified for the North Carolina Foothills and Western Piedmont.
Coming Up: In part five of the series, daylight reveals the first issues of this multi-faceted weather catastrophe and for the forecasting community the reality sets in that things will become a whole lot worse before it gets better. Part 5 will be made available Friday morning at our website.