On Monday, September 23, Potential Tropical Cyclone Helena formed in the western Caribbean Sea and strengthened into a tropical storm as it moved over the warm waters of the southern Gulf of Mexico on Tuesday before eventually becoming a hurricane on Wednesday. As the storm approached the Florida Big Bend on Wednesday and Thursday, it continued to gain momentum and strength, reaching major hurricane status (Category 3) on Thursday afternoon. Helene continued to move to the Florida Big Bend and made landfall near Perry shortly before midnight as a Category 4 hurricane with 140 mph winds. Helene maintained hurricane strength as it moved through southern Georgia, becoming a strong tropical storm as it passed east of Macon and Athens. By Friday morning, Helene was still a tropical storm centered near Franklin, Tennessee.
Helene’s wind field extended over 200 miles from the center of circulation. Tropical storm-force gusts were reported across much of the state, including most of the Midlands and Lowcountry, and hurricane-strength gusts were observed at locations along the Savannah River and the Upstate. The National Weather Service station at the Anderson Regional Airport reported a maximum wind gust of 72 mph. Many Upstate stations reported gusts over 60 mph. The Beaufort MCAS station measured a wind gust of 75 mph. While no notable storm surge was reported during the storm, tidal levels at the Charleston Harbor gauge ranged between 7.03 and 7.13 feet MLLW on Monday and Tuesday and reached 8.02 feet MLLW on Friday morning, causing saltwater flooding in low-lying coastal areas.
As of the initial posting of this report, fourteen confirmed tornadoes, including three EF1 and eleven EF0, have been reported across Beaufort, Colleton, Charleston, Georgetown, Horry, Marion, Orangeburg, and Sumter counties. Damage surveys are still being conducted across the state.
Information and data on rainfall and riverine impacts are outlined below.
Upon completion, a full Open-File Report with more detailed information on Helene will be linked here.
(Note: The highest and lowest official temperatures and highest precipitation totals provided below are based on observations from the National Weather Service (NWS) Cooperative Observer network and the National Weather Service's Forecast Offices.)Weekly* | Since Jan 1 | Departure | |
---|---|---|---|
Anderson Airport | 9.42 | 46.09 | 11.0 |
Greer Airport | 8.63 | 47.26 | 9.7 |
Charlotte, NC Airport | 5.62 | 45.54 | 12.1 |
Columbia Metro Airport | 5.60 | 45.72 | 10.2 |
Orangeburg 2 (COOP) | 4.19 | 41.03 | 1.1 |
Augusta, GA Airport | 5.65 | 37.13 | 4.5 |
Florence Airport | 3.05 | 43.46 | 7.7 |
North Myrtle Beach Airport | 0.78 | 43.78 | 6.1 | Charleston Air Force Base | 2.05 | 47.83 | 5.9 |
Savannah, GA Airport | 4.19 | 49.26 | 10.6 |
*Weekly precipitation totals ending midnight Sunday. M - denotes total with missing values. s - denotes total with suspect data. |
4-inch depth soil temperature: Clinton: Not Available. Columbia: 77 degrees. Barnwell: 70 degrees. Mullins: 73 degrees.
Predecessor rainfall and heavy rains from Helene fell across the state, starting on Wednesday and lasting through Saturday. Areas north and west of the Interstate 20 and Interstate 77 corridors received six to eighteen inches of rain, with the higher amounts falling north of the Interstate 85 corridor. The National Weather Service station near Jocassee reported a total of 18.21 inches of rain in two days; unfortunately, the station stopped reporting and is missing data during the event. CoCoRaHS observers in Greenville, Oconee, and Pickens County reported over a foot of rain, and one observer near Slater-Marietta recorded 18.12 inches of rain. Portions of the Central Savannah River Area reported close to a foot of rain, and ten inches of rain was recorded on the eastern side of Richland County. Counties along the lower Savannah measured four to six inches from the system, while most locations in the Pee Dee and Lowcountry reported totals of less than four inches of rain.
The U.S. Drought Monitor map released on Thursday, September 26, reflected the drier-than-normal conditions across parts of the Upstate, with severe drought (D2) conditions extending along the Savannah River from Oconee County to Edgefield County. Moderate drought (D1) was still observed in most of the CSRA, the Midlands, and parts of the interior Lowcountry, and abnormally dry (D0) conditions lingered in parts of the Pee Dee and the coastal Lowcountry. Any changes in the USDM drought designations from Helene’s rainfall will be reflected in the map released on Thursday, October 3, because most of Helene's rainfall fell after Tuesday morning's data cutoff.
Rainfall from Helene caused the 14-day average streamflow values at most of the gauges across the state’s watersheds to report values much above average, including the gauges in the Upper Savannah and Saluda river basins that had been experiencing low flows due to the persistent dry conditions. River height gauges rose into the moderate and major flood stage in response to the locally observed heavy rain, and in the Broad River Basin, from the water flowing out of western North Carolina.