Hurricane Debby Poses Serious Flood Threat To Southeast

Hurricane Central

By weather.com meteorologists

less than an hour ago

At a Glance

Hurricane Debby is expected to make landfall soon in Florida's Big Bend.
Extreme rain amounts may fall from northern Florida to coastal South Carolina and North Carolina, triggering serious flooding.
Gusty winds, storm-surge flooding and a few tornadoes will continue to be impacts, as well.

Hurricane Debby is nearing landfall in Florida's Big Bend region, which will be followed by a halt in its forward speed that could result in historically heavy rainfall triggering flooding in parts of the Southeast. Dangerous storm surge, strong winds gusts and a few tornadoes are also accompanying Debby.

(LIVE UPDATES: The Latest On Debby's Impacts)

Flash flooding is the number one concern with Debby. NOAA has issued their highest level of flood outlook for both Monday and Tuesday, shown in pink on the maps below. These areas could experience damaging and life-threatening flooding flash flooding and river flooding

The National Hurricane Center stated in their Monday morning discussion that "potentially historic heavy rainfall across southeast Georgia and the coastal plain of South Carolina through Saturday morning will likely result in areas of catastrophic flooding."

Flooding from rainfall could be exacerbated by winds blowing onshore along the Southeast coast. That can prevent floodwaters from draining away toward the ocean.

(MORE: Why You Should Pay Attention To High Risk Flood Forecasts)

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Here's where Debby is now and its forecast path. The hurricane is spreading heavy rain from the Florida Peninsula to southern Georgia this morning, triggering some flash flood warnings.

A tornado watch is in effect until 4 p.m. EDT for northern and central Florida and southeast Georgia.

Winds have gusted up to 98 mph in Florida's Big Bend near Horseshoe Beach this morning. Moderate coastal flooding from more than 4 feet of storm surge has been observed in Cedar Key.

(MAPS: Spaghetti Models, Satellite, Current Observations And More)

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After landfall, Debby will track northeast for a time over southern Georgia before slowing down and then meandering near the Southeast coast much of this week. While it could restrengthen some if the center moves back over water, the main result of the stalled forward motion is that its impacts in the Southeast, especially serious flooding, will be prolonged.

The slower a tropical system moves, the greater the rainfall. A study released last year by the NHC found rainfall flooding was responsible for the most direct U.S. deaths from tropical storms and hurricanes since 2013.

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Here's where warnings are in effect: A hurricane warning is in effect for the Florida Big Bend region from Indian Pass to Yankeetown.

Tropical storm warnings cover the rest of western and northern Florida into southern Georgia and coastal South Carolina.

A storm surge warning has also been issued in the Florida Big Bend from the middle of Longboat Key northward to the Indian Pass and for the Georgia and South Carolina coasts. Life-threatening storm surge is expected in these areas.

Breaking Down The Impacts

Rainfall Flooding Forecast

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As noted before, Debby's biggest threat is flash flooding and river flooding from heavy rainfall through the week ahead.

Rainfall totals of 6 to 12 inches (locally up to 18 inches) are possible across parts of central and northern Florida this week. Rainfall totals of 10 to 20 inches are a concern in portions of southeast Georgia and the South Carolina coastal plain and southeast North Carolina, with localized amounts up to 30 inches possible through Saturday morning.

Here's the timing of the most serious flood threat for the next few days, based on excessive rainfall outlooks from NOAA's Weather Prediction Center.

Monday-Monday Night: northern and central Florida to southeast Georgia and southern South Carolina.
Tuesday-Tuesday Night: northeast Florida to eastern Georgia, middle and lower South Carolina and southern North Carolina. Lingering heavy rain might continue as far south as central Florida.
Wednesday-Wednesday Night: Southeast Georgia to middle and lower South Carolina, eastern North Carolina and southeast Virginia.
Thursday-Friday: The threat of flooding rain might continue in parts of the Carolinas and Virginia, but details are uncertain.

(For even more granular weather data tracking in your area, view your 15-minute details forecast in our Premium Pro experience.)

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Storm Surge

Coastal flooding from storm surge is possible on the western coast of Florida Monday.

The surge could reach 6 to 10 feet above normal tide levels if the peak surge arrives at high tide in Florida's Big Bend. Most other areas could see a storm surge of 2 to 6 feet, including Tampa Bay and Charlotte Harbor.

Eventually, coastal flooding could affect the Southeast coast early next week, with 2 to 4 feet currently expected for parts of the Georgia and South Carolina coasts. Not only that, the onshore winds on the Southeast coast might worsen rainfall flooding by not letting water drain out toward the ocean.

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Wind And Tornado Threats

Gusty winds will spread northward across northern Florida on Monday, then the Georgia and South Carolina coasts on Tuesday and Wednesday. The times on the map below are indicative of when you should have all preparations complete.

Stronger wind gusts will cause more power outages or tree damage, especially near and inland from where the eventual center of the system tracks.