As Debby Winds Down, the Atlantic Cranks Back Up
Considerable flash flood threat continues from the Carolinas to New England this week, then eyes back on the Atlantic for next week
The long and soggy saga of Debby continues today, though the storm is finally starting to move after days upon days of meandering along the southeast U.S. coastline.
After making a second landfall in South Carolina during the overnight hours about 25 miles northeast of Charleston, the storm will gradually lose tropical organization today and should unwind by tomorrow as it merges with an approaching cold front.
Though the circulation may be spinning down, the rich tropical air will continue to wring out copious rainfall and bring considerable flooding from the South Carolina Midlands and North Carolina Piedmont today into the Mid-Atlantic and Northeast states through Saturday morning. Because most of these areas, including parts of New England, are already so saturated, rain rates of just an inch or two an hour could cause major flash flooding, especially in mountainous terrain.
A few tornadoes are also possible across parts of North Carolina and central Virginia today.
Though Debby has spread a wide and impressive swath of heavy rain totaling 15 to 20 inches across parts of Florida, southeast Georgia, and South Carolina, it’s so far largely underachieved the higher amounts earlier forecasts indicated were possible. For those who were flooded, this is little consolation, but the peak amounts will probably fall short of some of the biggest Carolina soakers like Florence in 2018 and the Joaquin-induced flooding of October 2015.
Tropical trouble brewing for next week?
In newsletters three weeks ago, we previewed a busy stretch as we turned the calendar to August. The Atlantic isn’t going to stay silent for long – not in a year like this one – and Debby appears to be just the start of an active run.
As we began discussing in this newsletter on Tuesday, a tropical disturbance pushing through the eastern Atlantic is expected to approach the easternmost islands of the Caribbean beginning late next Monday into mid-week, where development is possible.
On Thursday, the National Hurricane Center added this potential development area to its tropical outlook.
There’s reason to pay attention to this one, as now most of our reliable forecast models show a development signal, with perhaps more significant development by later next week as it nears the southwest Atlantic.
The concern first is any development that happens as the system approaches the islands, particularly the Greater Antilles, by mid-week. Beyond mid-week, in a steering setup reminiscent of Debby’s as it approached the southeastern Bahamas last week, we should begin to see a bend northward as a jet stream dips off the southeast U.S. coast.
The million-dollar-question is does it bend east of Florida or miss the dip and slide westward for next weekend. The current consensus leans toward a turn before reaching Florida, but it’s far too soon to rule anything out. The animation below shows how “jumpy” the ensemble average is this far out, with the scenarios showing a noticeably farther east solution just 24 hours ago.
Let’s give this some time to shake out before we get mired down in possible outcomes. We have plenty of time to watch the trends back here on the mainland but those with interests in the islands should monitor the forecasts closely over the weekend.
I think the next onme will be a miss and out to sea. That bend southwestward doesn't make a whole lot of sense. Nature doesn't do those things. Why would she start NOW? I think the jet will pick it up and do the recurve.