Debby nearly a hurricane; has Florida, Georgia and Carolinas on alert

Hurricane warnings are in place along the Florida coast as Tropical Storm Debby strengthens and approaches the state.

Tropical Storm Debby will continue to strengthen this weekend as it moves north just off the Florida Peninsula's Gulf coast, 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 this 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 Sunday night 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 Sunday, the center of Debby was about 100 miles west of Tampa, Florida, and 90 miles southwest of Cedar Key, Florida, with maximum winds of 70 miles per hour—a hurricane has winds of 74 mph or greater. It was moving to the north-north at 12 mph. Debby was developing an eye over the eastern Gulf, which is a sign of significant strengthening.

Storm surge flooding, up to a few feet, has occurred in Fort Myers Beach, Florida. Significant overwash was occurring in St. Petersburg, Florida. Water levels will rise significantly in Tampa Bay, Florida, during Sunday night. Rainfall this weekend has topped 8 inches in Sarasota, Florida, with more than 3 inches falling in Miami, Tampa and Fort Myers. Conditions will deteriorate through Sunday night and into Monday morning along the upper Gulf coast of Florida.

A hurricane warning is in effect for the Big Bend area of the Florida coast from the Suwannee River to Indian Pass. A tropical storm warning is in effect for much of the rest of Florida's Gulf Coast, including Tampa, Sarasota and Naples. A tropical storm warning was also in effect for part of the Atlantic coast from Ponte Verde Beach to the Savannah River.

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. On Sunday, South Carolina joined the growing list with a state of emergency in effect.

Where is Debby heading?

"As Debby approaches the Big Bend of Florida into 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 is expected to make landfall before noon on Monday, perhaps near Cedar Key, Florida.

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"Since Debby will stay over the Gulf through Sunday night, it will have enough time to quickly ramp up in intensity 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 curved shape of the coastline of Apalachee Bay may also help the storm strengthen at the last minute.

Debby may bring impacts more similar to a Category 3

Debby is rated a 3 for the U.S. on the AccuWeather RealImpact™ Scale for Hurricanes due to dangerous storm surge, life-threatening flooding from torrential rain and strong winds.

“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 northward into Tuesday, much of the Florida Peninsula, southeastern Georgia and coastal South Carolina 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 up to 10-15 feet is projected along part of Apalachee Bay. A storm surge of 3-6 feet will be more common with locally higher levels to 10 feet along the balance of the Florida Peninsula's west coast.

Meanwhile, the storm surge along the upper Atlantic coast of Florida will generally be 1-3 feet with locally higher amounts.

Into much of the balance of this week, heavy rain, windy conditions and locally severe thunderstorms will slowly spread north along the Atlantic coast of the southeastern U.S.

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, it will likely emerge over the Atlantic somewhere along the northern Florida or Georgia coast on Tuesday or Wednesday.

Widespread wind gusts of strong tropical storm force with some gusts to hurricane force will occur from northern Florida to the Carolina coast. the AccuWeather Local StormMax™ wind gust for Debby is 120 mph along the shores of Apalachee Bay, near where the eye of the storm first arrives on the coast.

The strain on trees in the region will be significant, especially in areas where the soil was saturated prior to Debby's arrival. With this in mind, a regional power outages are likely.

In some areas where the power is out, there may be no means of keeping cool and refrigerating food during cleanup operations in the wake of the storm for days.

"Steering breezes, which will guide Debby slowly but steadily along through the weekend, are forecast to weaken early this 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 week, there is the potential for excess rainfall that can lead to major flooding."

The AccuWeather Local StormMax™ rainfall for the Carolina and Georgia coast is 32 inches. This rainfall estimate is based on slow movement. Should Debby completely stall or loop over the region, rainfall amounts may be significantly higher, and much heavier rain may also fall farther inland over Georgia and the Carolinas.

On the Atlantic coast, because of Debby's anticipated slow forward speed, coastal cities such as Charleston, South Carolina, and part of the Savannah, Georgia, area 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 this 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 mid- to late week, 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 this 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.

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