NATIONAL STORM SUMMARY

SEPTEMBER 2024

1-7:Weekly rainfall totals of 4 to 8 inches or more were commonly observed in central and coastal Texas, southern Louisiana, and the northern half of Florida’s peninsula.

As the new month began, rain shifted southward. Still, daily record totals for September 1 reached 2.68 inches in Raleigh Durham, NC, and 2.01 inches in Jackson, TN. Meanwhile, quasi-organized tropical moisture interacting with a cold front led to local downpours in Texas. For example, daily-record totals for September 2, Labor Day, included 5.60 inches in Galveston and 3.63 inches in Midland. For Midland, it was the sixth-wettest day on record, and wettest day at any time of year since September 28, 2012, when 4.66 inches fell. Additional daily records in Texas on September 3 included 4.56 inches in Del Rio and 1.87 inches in San Angelo. That represented Del Rio’s third-wettest September day on record, behind 5.25 inches on September 22, 1919, and 5.21 inches on September 26, 1970. The mid- to late week period featured additional heavy showers across the Deep South. In Louisiana, daily-record amounts reached 3.02 inches (on the 4th) in Alexandria; 2.19 inches (on the 5th) in Monroe; and 3.19 inches (on the 6th) in New Orleans. Baton Rouge, LA, collected 4.12 inches, not a record for the date, on September 5. New Orleans received at least an inch each day from September 4-6, totaling 6.54 inches.

8-12: On September 11, Francine became the third and strongest hurricane of the season to strike the U.S. Gulf Coast, following Beryl (in Texas) in early July and Debby (in Florida) in early August. Francine briefly achieved sustained winds near 100 mph while making landfall around 5 pm CDT in Louisiana’s Terrebonne Parish. Hurricane-force wind gusts (74 mph or higher) spread as far inland as New Orleans, where a gust to 78 mph was clocked at Louis Armstrong International Airport.

On September 11, daily-record totals included 7.33 inches in New Orleans, LA, and 4.14 inches in Gulfport, MS. For New Orleans, it was the second-wettest September day on record, behind only 7.52 inches on September 25, 2002. Peak wind gusts on September 12 associated with Francine’s squalls were clocked to 57 mph in Memphis, TN; 51 mph in Huntsville, AL; and 50 mph in Jonesboro, AR. On September 12, Apalachicola, FL, received a daily-record sum of 6.29 inches, helping to boost the 3-day (September 11-13) total to 12.77 inches. Elsewhere on the 12th, daily-record totals reached 4.22 inches in Memphis, TN; 3.95 inches in Jonesboro, AR; and 3.05 inches in Tupelo, MS. By September 13, rain loosely associated with the remnants of Francine spread as far east as Georgia, where Columbus collected a daily-record total of 3.22 inches. In Alabama, daily-record amounts for September 14 totaled 4.72 inches in Muscle Shoals and 3.63 inches in Birmingham. Meanwhile, heavy showers developed along the middle Atlantic Coast, where Cape Hatteras, NC, netted a daily-record sum (4.59 inches) for September 13. Farther west, a pattern-changing cold front delivered some Northwestern moisture, including high elevation snow, with daily-record totals for September 11 being set in locations such as Olympia, WA (0.93 inch); Roseburg, OR (0.54 inch); and Alturas, CA (0.35 inch). Late in the week, cooler, more humid weather aided wildfire containment efforts in southern California, where the Bridge, Line, and Airport Fires collectively burned more than 115,000 acres of vegetation during the first half of September.

15-21: Potential Tropical Cyclone Eight failed to achieve tropical characteristics before moving ashore on September 16 over northeastern South Carolina. Nonetheless, heavy rain spread inland across the middle Atlantic States, with significant flooding in southeastern North Carolina amid downpours locally ranging from 10 to 18 inches. Farther west, rainfall associated with the remnants of Hurricane Francine finally subsided early in the week, following multi-day totals of 5 to 10 inches or more from the northern Mississippi Delta to the panhandle of Florida.

Later, heavy rain developed on the northern High Plains, preceded by gusty winds. In South Dakota, peak gusts on September 17 were clocked to 93 mph in Faith and 60 mph in Rapid City. On the 18th, Lewistown, MT, experienced its wettest September day on record; the total of 4.35 inches shattered the record of 1.76 inches, set on September 21, 1959. With a total of 1.52 inches on the 18th, Havre, MT, noted its wettest September day since September 25, 1986, when 1.95 inches fell. With mid- to late week thunderstorms dotting the remainder of the Plains, drought-affected areas experienced localized relief. For example, Dodge City, KS, reported a daily-record sum of 2.05 inches on September 18. At week’s end, heavy rain grazed coastal Massachusetts. Although Boston received September 19-22 rainfall totaling just 0.97 inch, parts of Cape Cod measured more than 6 inches, with several higher-than-average tide cycles in parts of the northern and middle Atlantic States resulting in coastal flooding.

22-28: Hurricane Helene delivered deadly flooding across the southern Appalachians, following a record-setting storm surge from Florida’s Big Bend to Tampa Bay. In addition, a swath of extreme winds from the Category 4 storm swept across north-central Florida into south central Georgia, snapping trees, including commercial timber. The cumulative effects of Helene, the strongest hurricane to strike that section of the U.S. Gulf Coast in the nation’s history, were widespread and devastating, leaving millions without power and resulting in more than 100 fatalities. Catastrophic damage extended from coastal areas to agricultural communities to portions of mid-size and large cities, including Atlanta, GA; Greenville Spartanburg, SC; and Asheville, NC. Helene officially made landfall around 11:10 pm EDT on September 26 near Perry, FL, with maximum sustained winds near 140 mph. The fast forward speed of the hurricane at landfall allowed hurricane-force wind gusts (74 mph or greater) to push well inland, across much of Georgia and into the southern Appalachians.  Inland flooding was exacerbated by the fact that extremely heavy rain had fallen just prior to Helene’s arrival, especially in parts of western North Carolina.  Helene nearly perpendicular path across mountain ranges maximized rainfall in the southern Appalachians. Before spinning down, Helene’s remnants contributed to heavy rain as far west as Kentucky and Tennessee, as well as neighboring areas of the lower Midwest.

Helene acquired enough definition to be named on September 24, while located about 175 miles south of the western tip of Cuba. Approximately 60 hours later, the suddenly intense storm slammed into Florida’s Big Bend. A record storm surge of 9.68 feet was reported near the time of landfall in Steinhatchee, FL, topping the high-water mark of 8.03 feet set just 13 months ago during the passage of Category 3 Hurricane Idalia. Similarly, Cedar Key, FL, reported a record storm surge of 9.31 feet, well above Idalia’s standard of 6.84 feet, set on August 30, 2023. The surge reached 6.67 feet as far south as Clearwater Beach, FL, well above Idalia’s record of 4.05 feet. The Tampa Bay area also dealt with strong winds, which late on the 26th gusted to 82 mph at Albert Whitted Airport in St. Petersburg, and 74 mph in Sarasota-Bradenton. Later, as Helene punched inland, a gust to 100 mph was clocked on September 27 in Alma, GA. Hurricane-force gusts extended to the Georgia coast, where Savannah reported 76 mph. Elsewhere in the Southeast, peak gusts on the 27th included 82 mph in Augusta, GA, and 73 mph in Columbia, SC. Precipitation was an even bigger story, especially when considering rain that fell in advance of Helene’s arrival. Atlanta, GA, received more than 3 inches of rain each day from September 25-27, totaling 11.12 inches. Asheville, NC, was even harder hit, with a 3-day sum of 13.98 inches. The pre-Helene deluge in Asheville included totals of 4.09 and 5.78 inches, respectively, on September 25-26. Prior to this event, Asheville’s highest calendar-day total during September had been 4.40 inches, on September 29, 1964. Additionally, Asheville completed its wettest month on record, with the 17.90-inch total surpassing 14.68 inches in May 2018. Isolated 3 day totals ranging from 20 to 30 inches were reported in mountainous areas of western North Carolina. Horrific flooding ensued, with many record crests being reported on September 27-28 along the French Broad River and many of its tributaries. In Asheville, the French Broad River crested 15.17 feet above flood stage on the 27th, smashing the July 1916 high-water mark by 1.57 feet. Several crest records were also set across northern Georgia and northwestern South Carolina, with the Saluda River near Greenville, SC, cresting 10.73 feet above flood stage on September 28— and 0.85 foot above the October 1949 record. Heavy rain extended well west of the Appalachians, with Paducah, KY (5.33 inches on the 27th), experiencing its second-wettest September day on record, behind only 7.49 inches on September 5, 1985, in conjunction with the remnants of Hurricane Elena.

Jim G. Munley, jr.
http://www.jimmunleywx.com