A strengthening tropical depression is poised to become Hurricane Isaias and hit parts of the southern United States this week with heavy rain and strong winds. Tropical Depression Nine has sustained winds of 35 mph and was located about 600 miles south of the mouth of the Mississippi River on Tuesday night. Receive live updates and alerts. Download the CNN Weather app. The system is expected to move east over the Yucatan Peninsula and then turn sharply north toward the northern Gulf Coast. It is forecast to rapidly strengthen into a Category 2 hurricane with 100 mph winds by Friday. Isaias will likely bring flooding, strong winds and storm surge to areas from southern Louisiana to the Florida Panhandle beginning Friday. The storm could also spawn several tornadoes as its rain bands hit the coast. This will be the first hurricane of the year in the Atlantic basin, ending a record wait linked to the effects of a probable El Niño of record intensity. It’s not yet clear exactly where the storm could track or how strong it will be as it approaches land, but anyone along the Gulf Coast, from Louisiana to Florida’s Big Bend, should keep a close eye on the forecast. Florida Gov. Ron DeSantis on Tuesday declared a state of emergency for 25 counties ahead of the storm, urging residents to prepare disaster plans and stockpile hurricane supply kits. State emergency crews are placing generators, fuel, food, water and flood barriers in the Tallahassee and Santa Rosa areas to support the response. Oil companies are also taking precautions in the Gulf. Shell is evacuating non-essential staff from six offshore platforms, while BP is removing non-essential workers and securing its offshore facilities, the companies said on Tuesday. This storm is passing through El Niño-influenced atmospheric conditions that have so far largely hampered tropical systems during the Atlantic hurricane season. The Gulf waters have record temperatures for this time of year and provide plenty of fuel, but that’s only part of the equation. The bane of Atlantic tropical systems this season has been wind shear. This refers to winds that blow at different speeds and from different directions at various levels of the atmosphere. Wind shear can destroy tropical storms and hurricanes. This new system benefits from low wind shear in the southern Gulf, but will find higher wind shear shielding the Gulf Coast to the north, threatening to tear apart the storm as it approaches. But the system is also expected to move quickly, so its exposure to increased wind shear may be limited. If the storm were to move more slowly, it could quickly weaken as it meanders through hostile conditions. The force and path of the storm are also intertwined. A stronger storm’s circulation extends higher into the atmosphere, allowing the winds at those heights to direct it differently than a weaker system. That path, in turn, will determine how much time it spends over warm waters and how much hostile wind shear it encounters, which will determine its strength when it reaches shore. Regardless of its final destination, heavy rain is a cause for concern along the Gulf Coast and elsewhere in the South later this week. The storm could bring 3 to 6 inches of rain, with localized rainfall of up to 10 inches in some spots, from southern Louisiana to the Florida Panhandle and Big Bend. Showers could begin to increase along the coast on Friday and then continue to soak the region as they move inland over the weekend. As this year has already shown, it doesn’t take a hurricane-strength system to cause significant impacts, particularly in a warming world that is making tropical systems wetter. Tropical Storms Arthur and Edouard did not last long, but their heavy rains caused significant flash flooding and water rescues. Parts of Louisiana and Mississippi were hit hardest by Arthur’s flooding, while Edouard dropped more than 20 inches of rain on East Texas. Determining the location and severity of any storm surge, flooding, high winds and tornadoes along the northern Gulf Coast is even more difficult at this time because we need to know how strong the storm will be and exactly where it will move. The earliest those impacts could arrive is Friday or Saturday night. What’s Typical in October and November Four named storms (that is, tropical storm strength or greater) typically form in October and November, but some hurricane seasons may end stronger while others calm down. The last few years illustrate this ebb and flow year after year. Seven storms formed during October and November 2024, but only two formed during the same period in 2023. Late storms tend to form closer to the United States, including in the Gulf, Caribbean, and off the southeast coast, making them more likely to impact land. While there are usually fewer storms, they can still be destructive. Last year, Category 5 Hurricane Melissa devastated Jamaica in the last week of October. Hurricane Michael hit the Florida Panhandle on October 10, 2018, becoming the last Category 5 landfall on record in the U.S. And Hurricane Sandy may be the most notorious of all: It transformed into a hybrid superstorm in late October 2012 and hit the East Coast. Super El Niño’s grip on the Atlantic basin means a repeat of the notorious late-season hurricanes is less likely this year. Its storm-killing wind is the main reason this season could be hurricane-free for the first time in reliable records.
