Tropical Storm Debby has Florida, southeast US on alert

A hurricane warning has been issued for part of Florida as Tropical Storm Debby strengthens as it approaches the state.

Tropical Storm Debby will continue to strengthen as it moves north just off the Florida Peninsula's Gulf coast this weekend, spreading rain, gusty winds and severe thunderstorms across the state. AccuWeather meteorologists warn that it may intensify into a hurricane before making landfall, most likely in northern Florida, and then could stall along the Carolina coast next week, which may add significantly to life-threatening conditions.

AccuWeather dubbed the wave of low pressure a tropical rainstorm on Monday, July 29, to raise public awareness as it approached the Leeward Islands with drenching showers and thunderstorms. During the rest of the week, the tropical rainstorm pushed slowly but steadily west across Puerto Rico, Hispaniola and Cuba. It strengthened into Tropical Storm Debby at 5 p.m. EDT Saturday.

Debby's impacts on Florida will increase through this weekend and as it approaches the northeastern Gulf coast, it will likely strengthen to a Category 1 hurricane.

The latest on Tropical Storm Debby

As of 8 p.m. EDT Saturday, the center of Debby was about 100 miles west-southwest of Key West, Florida, with maximum winds of 40 miles per hour. It was moving to the northwest at 14 mph.

A hurricane warning has been issued for the Big Bend area of the Florida coast between the Suwannee River and the Ocholckonee River. A tropical storm warning is in effect for much of the rest of Florida's Gulf Coast, including Tampa, Sarasota and Naples.

A state of emergency was declared in Florida on Thursday evening, a move that opened up additional resources to the state to prepare for the approaching storm. On Saturday a state of emergency was declared for Georgia. Evacuation orders were issued for some low-lying areas of the Florida coastline on Saturday.

Where is Debby heading?

"As Debby pulls away from Cuba and then moves over the eastern Gulf of Mexico this weekend, we expect it to gain strength. As Debby approaches the Big Bend of Florida early Monday, further intensification to a Category 1 hurricane can occur," AccuWeather Lead Hurricane Expert Alex DaSilva said.

Water temperatures over the eastern Gulf of Mexico are in the mid- to upper 80s degrees Fahrenheit, which is well above the minimum threshold of 78 degrees for tropical development. Wind shear, or disruptive steady or shifting breezes, is light in the area where the tropical storm is headed. Moisture is also plentiful around the eastern Gulf. Factoring in these conditions, strengthening is likely.

How much strengthening occurs will depend on how much time the center of Debby spends over the warm water.

Debby will interact with the land mass of the Florida Peninsula but will likely remain about 100 miles or so offshore through much of Sunday.

• Have the app? Unlock AccuWeather Alerts™ with Premium+

"Since Debby will stay over the Gulf through Sunday night, it will have enough time to quickly ramp up and become a strong tropical storm or hurricane before pushing inland over northern Florida," DaSilva warned.

There is even the potential for Debby to rapidly intensify before making landfall along the shores of Apalachee Bay, Florida. Rapid intensification occurs when the maximum sustained winds in a tropical storm or hurricane increase by 35 mph or greater in 24 hours or less.

Hurricane Beryl experienced rapid intensification earlier this summer. Ian is an example of a hurricane that experienced two rounds of rapid intensification in 2022.

The AccuWeather RealImpact™ Scale for Hurricanes with the feature is a 2 for the U.S.

“Debby will produce a variety of life-threatening and significant impacts for days to come," AccuWeather Chief Meteorologist Jonathon Porter said, "This storm is going to make for a dangerous and long week for people in parts of the southeastern U.S."

The AccuWeather scale is not based on wind intensity alone, like the Saffir-Simpson Hurricane Wind Scale, but rather takes into consideration all weather factors, from wind to rain, storm surge, and severe thunderstorms, as well as impacts on the population and economy.

Porter urged people to not be lulled into any false sense of security because Debby is presently rated as a tropical storm on the Saffir-Simpson Hurricane Wind Scale.

"Tragically, we have seen many situations in the past where people have not prepared to the level that matched the dangerous threats that exist from such a storm due to the limitations of the Saffir-Simpson scale, used by most meteorologists and the National Hurricane Center for decades, which only categorizes a tropical storm or hurricane by its wind intensity," Porter said.

Such storms have included Florence in the Carolinas in 2018, which made landfall as a Category 1 hurricane on the Saffir-Simpson scale but would have been a 4 on AccuWeather RealImpact™ Scale for Hurricanes as a result of the catastrophic flooding it produced.”

As Debby spins north this weekend, much of the Florida Peninsula will be on the storm's eastern flank, which can be a trouble spot for tornadoes.

Waterspouts will be spawned in coastal areas. Bands of heavy rain and gusty thunderstorms will increase over the peninsula and the northern part of the Florida mainland, regardless of the number of tornadoes and waterspouts.

Surf will build north over Florida and along the northern Gulf coast this weekend and later along the coastal areas of Georgia and the Carolinas. Swimmers will need to exercise extreme caution and obey local restrictions, as rip currents will increase in strength and number.

Enough rain will fall on Florida this weekend to trigger slow travel with areas of urban and low-lying area flooding. Rainfall rates of several inches per hour can occur in extreme cases.

The intensity and track of Debby will determine the storm surge along the Florida Gulf coast. At this time a water rise of 6-10 feet is projected along some of the bays where water becomes trapped with the highest surge along a portion of Apalachee Bay.

This magnitude of storm surge is most likely near and just south of where the center of the storm moves inland.

Later this weekend to early next week, heavy rain, windy conditions and locally severe thunderstorms will spread into part of the mainland of the southeastern United States.

Debby to re-emerge in Atlantic, possibly strengthen 2nd time

The slow movement of the storm will result in considerable time over land, which will cause Debby to weaken later Monday and Monday night.

Regardless of where Debby makes landfall in Florida this weekend, it will likely emerge over the Atlantic somewhere along the northern Florida or Georgia coast on Tuesday.

"Steering breezes, which will guide Debby slowly but steadily along through the weekend, are forecast to weaken early next week, and that could create a big problem along the southern Atlantic coast," AccuWeather Chief On-Air Meteorologist Bernie Rayno said, "Should Debby stall along the Carolina coast early next week, there is the potential for excess rainfall that can lead to major flooding."

The AccuWeather Local StormMax™ rainfall for northeastern Florida and the Carolina and Georgia coast is 25 inches. This rainfall estimate is based on slow but steady movement. Should Debby stall, rainfall amounts may be significantly higher.

On the Atlantic coast, because of Debby's anticipated slow forward speed, coastal cities such as Charleston, South Carolina, and Savannah, Georgia, may face significant flooding from the combination of torrential rain and storm surge. A coastal water level rise of 6-10 feet is forecast along portions of the Georgia and South Carolina coasts.

"While the wind impact of this storm will be significant and dangerous, especially near the area where Debby makes its first U.S. landfall in Florida, this storm may end up being remembered for water dangers, especially in the Carolinas, due to significant storm surge and major flooding, which can even become a catastrophic flooding disaster in some places, if heavy rain bands persist over the same places for days in a row," Porter said, "Tragically, 85% or more of the direct fatalities from tropical storms and hurricanes have occurred in recent years as a result of these water dangers – being prepared and taking action, not underestimating all of the storm’s impacts, truly can save lives.”

Wind, rain and surf conditions will increase along the Carolinas to southeastern Virginia beginning on Monday or Tuesday with dangerous rip currents, storm surge flooding and beach erosion that may last for two to four days, depending on Debby's forward speed and intensity.

Should steering breezes remain steady due to a dip in the jet stream in the Northeast, the system may be pushed enough to be drawn north along the mid-Atlantic and New England coasts or possibly farther offshore over the Atlantic.

"Either way, there is the potential for the system to regain strength over the Atlantic early next week after its land interaction with Florida," DaSilva said. "That could mean it may become a hurricane for the first time or regain hurricane, assuming it strengthens before reaching Florida in the first place."

From Tuesday to Thursday, tropical moisture may interact with a non-tropical storm in the Northeast. That interaction may result in excessive rainfall and flooding well north and west, away from or removed from the tropical feature itself.

Even if Debby stays to the south, seas and surf will build along the mid-Atlantic and southern New England coasts next week.

Super-charged hurricane season anticipated

AccuWeather has not wavered from its prediction of a super-charged hurricane season for 2024 since this past winter.

Record-setting Category 5 Hurricane Beryl demonstrated the concern AccuWeather's team of experts had about the potential energy available to the extremely warm Atlantic waters.

As dry air diminishes and the effects of La Niña unfold late this summer and fall, great numbers of tropical storms and hurricanes are forecast, along with the likelihood of additional storms that intensify rapidly like Beryl did.

Want next-level safety, ad-free? Unlock advanced, hyperlocal severe weather alerts when you subscribe to Premium+ on the AccuWeather app. AccuWeather Alerts™ are prompted by our expert meteorologists who monitor and analyze dangerous weather risks 24/7 to keep you and your family safer.