You Ain't Goin' Nowhere: Tropical Storm Debby Update for August 7th

Debby's flood risks continue into the weekend from the Carolinas up the U.S. East Coast.

Florida and continental U.S. tropical threat synopsis: Tropical Storm Debby slowly will move back into South Carolina in the next day. The heaviest additional rainfall totals of 4-8” or more are likely in eastern South Carolina, central and western North Carolina, and Virginia through Friday. No tropical threats to Florida on the map.

Mood music:

Almanac: It’s Wednesday, August 7th… day 68 of the 2024 hurricane season, 115 days to go. By total storm energy, the season is 8.8%, 20.6%, and 13.3% complete for the Atlantic, continental U.S., and Florida, respectively.

Active storms: The broad center of Tropical Storm Debby is located about 60 miles southeast of Charleston, SC this morning, drifting east at 5 mph. Debby’s sustained winds remain 45 mph, almost all south or east of the center. Dry air aloft over the circulation is keeping deep convection to a minimum, but there are some 35-50 mph wind gusts and heavy rain onshore this morning between eastern SC and south-central NC, where Tropical Storm Warnings remain in effect and 1-2’ feet of storm surge are occurring. Otherwise Debby is bringing light to moderate showers and breezy conditions between Jacksonville and the Outer Banks.

Models are finally in decent agreement on what Debby will do over the next 3-4 days, with the center easing north later today and crossing the South Carolina coast early tomorrow with top winds of 50 mph. After landfall, Debby will accelerate north through the mid-Atlantic on Friday, then clear northern New England by mid-day Saturday as a post-tropical low.

Rain impacts remain Debby’s greatest threat to life and property. As Debby moves slowly north over the next 48 hours, areas from Charleston north into the Shenandoah Valley are most likely to see slow-moving heavy rainfall overhead capable of producing another 4-8” of rain, much of which will be falling on saturated ground. In coastal Georgia, some good news for you as the influx of dry air from the west should keep your rainfall over the next few days showery and tallying less than 1” more, so flood risks are subsiding. To the north, there is potential for a quick-hitting 2-5” of rain expected from Debby’s remnants between late Thursday and early Saturday, from the Delmarva region north across central/eastern PA and into the Adirondacks and Green Mountains.

These rainfall totals mean elevated risks of flash flooding in the eastern Carolinas through Friday and from northern Virginia into southeastern Canada later on Friday and early on Saturday. Risks may be particularly acute in mountainous areas that see high rainfall rates, especially as Vermont and northern New York have already been experiencing flooding issues this summer.

Overall, the endgame for Debby is becoming clearer as its time of goin’ nowhere comes to a close tomorrow. Expect another couple of wet days in the Southeast before the risks shift north across the U.S. East Coast Friday and Saturday. If you are in these areas, have a way of getting emergency weather warnings and keep highway travel to a minimum, particularly in lower-lying or flood-prone areas.

Disturbances in the NHC tropical weather outlook: A tropical wave in the southern Caribbean has a 10% chance of developing in the next seven days, mostly as it passes through the extreme southern Gulf this weekend. Land interaction with Central America should prevent development, and the wave will move into Mexico by Monday.

Elsewhere: A tropical wave emerging from the African coast today will struggle for the next 5 days through dry air, but there is for potential development near or north of the Lesser Antilles in 6-10 days. The initial steering pattern of western Atlantic troughing in early week 2 would signal anything that forms probably would remain out-to-sea, but I’ll keep an eye on it regardless.

Next update: Debby wrap-up column with a look at August climatology out tomorrow afternoon.