Gulf of Mexico: Hurricane Helene tracking northward away from the Yucatan Peninsula as of late Sept. 25 /update 4

Hurricane Helene is tracking northward in the Gulf of Mexico away from the Yucatan Peninsula, Mexico, late Sept. 25. As of 22:00 CDT, the system's center of circulation was approximately 680 km (425 miles) southwest of Tampa, Florida.

Forecast models indicate that the storm will strengthen further into a Category 4 hurricane as it tracks north-northeastward over the Gulf of Mexico Sept. 26 before making landfall over the Big Bend region of Florida late Sept. 26. After landfall, the system is expected to weaken into a tropical storm as it tracks northward over western Georgia early Sept. 27, before weakening further and transitioning into a post-tropical cyclone as it tracks northwestward over central Tennessee Sept. 27. The remnants of the system are expected to track westward over southwestern Kentucky through early Sept. 28 before turning around to track eastward along the southern Kentucky border through late Sept. 29. Some uncertainty remains in the track and intensity forecast, and significant changes could occur over the coming hours and days.

As of late Sept. 25, authorities have issued the following watches and warnings:

Hurricane Warning

• Anclote River to Mexico Beach, Florida

Hurricane Watch

• Englewood to Anclote River, including Tampa Bay, Florida

Tropical Storm Warning

• The Florida Keys, including Dry Tortugas, Florida

• Flamingo to Anclote River, including Tampa Bay, Florida

• West of Mexico Beach to the Okaloosa/Walton County Line, Florida

• Flamingo, Florida, northward to the Little River Inlet, South Carolina

• Lake Okeechobee, Florida

• Cuban provinces of Artemisa, Pinar del Rio, and the Isle of Youth

Storm Surge Warning

• Mexico Beach eastward and southward to Flamingo, Florida

• Tampa Bay, Florida

• Charlotte Harbor, Florida

Authorities will likely update and extend the coverage of the weather advisories over the coming hours and days as the storm system develops.

Hurricane conditions are expected in the hurricane warning area in the US late Sept. 26. Hurricane conditions are also possible in western Cuba late Sept. 26, with tropical storm conditions from late Sept. 27. Tropical storm conditions are expected in southern Florida late Sept. 25 and will spread northward across the rest of Florida, Georgia, and South Carolina through late Sept. 26.

The storm is forecast to generate rainfall amounts of 10-20 cm (4-8 inches) with isolated higher totals of around 30 cm (12 inches) across parts of western Cuba, the Cayman Islands, and the northeast Yucatan Peninsula in Mexico, bringing a risk of considerable flooding.

Rainfall amounts of 15-30 cm (6-12 inches) with isolated higher totals around 46 cm (18 inches) are expected over parts of the southeastern US and into the southern Appalachian mountains. This rainfall will likely result in catastrophic and potentially life-threatening flash and urban flooding and significant riverine flooding. Numerous landslides are likely in the steep terrain across the southern Appalachians. Isolated tornadoes are possible over parts of Florida late Sept. 25 before expanding northward across Florida into parts of Georgia and South Carolina Sept. 26.

Storm surge could raise water levels by as much as 0.6-1.2 meters (2-4 feet) above normal tide levels in areas of onshore winds along the southern coast of Pinar del Rio, Cuba, including the Isle of Youth, and 0.9-1.5 meters (2-4 feet) along the northern coast of the Yucatan Peninsula, Mexico.

Peak surge could reach up to 4.5-6 meters (15-20 feet) between Carrabelle and the Suwannee River in Florida, 3-4.5 meters (10-15 feet) from Apalachicola to Carrabelle and from Suwannee River to Chassahowitzka, and 0.9-3.7 meters (3-12 feet) along other parts of Florida's Gulf Coast. Swells generated by Helene will affect the southern coast of Cuba and the Yucatan Peninsula of Mexico over the coming days and will spread northward toward the west coast of Florida and the northeastern Gulf Coast late Sept. 25-26. These swells are likely to cause life-threatening surf and rip current conditions.

Florida Gov. Ron DeSantis declared a state of emergency across 41 of the state's 67 counties Sept. 23 before expanding it to 61 counties Sept. 24. Mandatory and voluntary evacuation orders are in place across 27 counties in Florida, including mandatory orders in parts of Charlotte, Citrus, Dixie, Franklin, Gulf, Hillsborough, Jefferson, Lafayette, Leon, Levy, Manatee, Pasco, Pinellas, Sarasota, Taylor, and Wakulla counties. A curfew is also in effect from sunrise to sunset in Taylor County. Voluntary evacuation orders are also in place for Haywood County in North Carolina. Authorities will likely issue further mandatory and voluntary evacuation orders across counties along the Panhandle, Tampa Bay area, and west coast of Florida as the storm approaches. Several schools and universities in Florida's Gulf Coast areas have been closed. Georgia Gov. Brian Kemp has also declared a state of emergency Sept. 24 due to the anticipated impacts from the storm. North Carolina Gov. Roy Cooper and South Carolina Gov. Henry McMaster also declared states of emergency Sept. 25. President Joe Biden approved a federal emergency declaration for Florida Sept. 24.

Airlines have canceled more than 450 flights across the southeastern US Sept. 26; Tallahassee, Tampa, and Fort Myers are the worst affected. Tampa International (TPA), St. Pete-Clearwater International (PIE), Peter O. Knight (TPF), Tampa Executive (VDF), and Plant City (PCM) airports will suspend operations Sept. 26; services could resume Sept. 27 once it is safe to do so.

Sir Captain Charles Kirkconnell International Airport (CYB) and Owen Roberts International Airport (GCM) in the Cayman Islands closed late Sept. 23 through Sept. 24, with flights resuming at 07:00 late Sept. 25. Banks, courts, and non-emergency health services were also closed across the Cayman Islands Sept. 24 and schools remain closed as of late Sept. 25. Cruise ship arrivals at ports in Quintana Roo State, Mexico, have been canceled late Sept. 24-25. Several shelters have been opened in northern Quintana Roo, and banks are closed in the region. Oil companies have evacuated personnel from some production platforms in the Gulf of Mexico.

Sustained heavy rainfall could trigger flooding in low-lying areas and those with easily overwhelmed drainage systems. If weather conditions prove hazardous, localized evacuations, flash flooding, and landslides are possible.

Inclement weather could trigger localized business, transport, and utility disruptions, rendering some bridges or roadways impassable. Flight disruptions at regional airports and temporary port closures are also possible. Stagnant pools of water during and after flooding increase insect- and waterborne diseases, such as dengue fever, cholera, and malaria. Exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.