An intense and historic flood disaster—unrelated to Hurricane Joaquin, but influenced by it—continues to unfold across the Carolinas this afternoon, with South Carolina taking the brunt of the tropical deluge. Some communities near Charleston have recorded more than two feet of rain in the past three days.
Last week, it looked like the East Coast was going to face a one-two punch of epic proportions. The first—and most dangerous—threat we thought we faced was from Hurricane Joaquin, a borderline category five storm near the Bahamas. For days, many of the weather models showed Joaquin curving into the East Coast, but thankfully, a trough in the jet stream kicked it out to sea.
However, an upper-level low developing in that very same trough promised to wring out every bit of tropical moisture over the southeast as it swung toward the ocean, and it did exactly that. A direct stream of atmospheric moisture from the tropics—heavily influenced by Hurricane Joaquin—allowed for a band of heavy rain to hose both South Carolina and North Carolina for days on end, even continuing as of the writing of this post.
(Mobile users, know before you tap ‘load’ that the gif below is 10 megabytes.)
Above is a long radar loop stretching from 4:00 PM EDT on Friday through 2:00 PM EDT on Sunday. The heaviest rain fell right along the I-26 corridor between Charleston and Columbia, dumping an unbelievable amount of condensed tropical moisture on saturated ground faster than natural and man-made water systems could handle.
These bands of rain are reminiscent of the persistent bands of lake effect snow that bury communities in western New York each winter. Although they’re created by completely different processes, the end result here is no different.
Some locations in South Carolina have reported more than two feet of rain in the past three days, and the rain still isn’t over yet. The above map shows rainfall over the past 14 days, with a wide swath of a foot or more over central and coastal South Carolina. Though the map stretches back two weeks, most of this rain has fallen since Friday.
- 6 miles northeast of Mount Pleasant, S.C.: 24.23”
- 3 miles south-southwest of Shadowmoss, S.C.: 22.47”
- 3 miles north-northeast of Huger, S.C.: 21.04”
- Gills Creek, S.C.: 18.39”
- 3 miles northwest of Summerville, S.C.: 17.23”
- Charleston Airport: 16.61”
- NWS Charleston: 16.49”
- Shaw Air Force Base: 14.34”
- Columbia Metro Airport: 9.50”
- 3 miles northeast of Walterboro, S.C.: 7.87”
On Saturday, Charleston Airport recorded 11.50” of rain, which shattered the record for the most rain they’ve ever recorded in one day, previously held by a 10.52” rainfall on September 21, 1998. Records at the Charleston Airport stretch back to March 1, 1938.
The integrity of many roads has been compromised resulting in bridge collapses and roads being washed out. pic.twitter.com/204Clafjos— Trooper David SCHP (@SCHP_Troop1) October 4, 2015
The result of this onslaught of water is some of the worst flooding residents have ever seen. Widespread evacuations and water rescues are underway in neighborhoods near bodies of water that are overflowing their banks. Local officials report that the city of Georgetown is under four feet of water.
Many roads and bridges are being washed away by the torrents of water as rivers and streams soar well above their normal height. The situation is so bad that the South Carolina Department of Public Safety reports that the entire 74-mile stretch of Interstate 95 between I-20 and I-26 is closed due to flooding.
The tide gauge in Charleston Harbor is at major flood stage, recording a value of 8.18 feet at 2:18 PM EDT. The Congaree River in Columbia is expected to crest in a major flood at 31.3 feet this afternoon, coming in well above its normal single-digit depth—however, we won’t be able to measure the crest of the Congaree’s flooding at this location, since the crushing force of the water swept away the river gauge.
Waters will slowly recede as the rainfall slows and comes to an end during the day on Monday.