Caribbean Sea: Tropical Storm Helene tracking northwestward across the northwestern Caribbean Sea as of Sept. 24 /update 1

Tropical Storm Helene is tracking northwestward across the northwestern Caribbean Sea Sept. 24. As of 11:00 EDT, the system's center of circulation was approximately 275 km (170 miles) south-southeast of the western tip of Cuba.

Forecast models indicate that the storm will strengthen as it tracks northwestward in the Caribbean Sea late Sept. 24 and will become a Category 1 hurricane as it passes through the Yucatan Channel close to the northeast coast of Quintana Roo State, Mexico, early Sept. 25. Helene is expected to strengthen further into a Category 3 hurricane as it tracks northward and then north-northeastward over the Gulf of Mexico Sept. 25-26, 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 Georgia early Sept. 27, before weakening further and dissipating as it tracks north-northwestward over eastern Tennessee, central Kentucky, and into Indiana Sept. 26-early Sept. 28. Some uncertainty remains in the track and intensity forecast, and significant changes could occur over the coming hours and days.

As of Sept. 24, authorities have issued the following watches and warnings:

Hurricane Watch

• Cabo Catoche to Tulum, Mexico

• Pinar del Rio Province, Cuba

• Englewood to Indian Pass, Florida

• Tampa Bay, Florida

Tropical Storm Warning

• Grand Cayman, Cayman Islands

• Rio Lagartos to Tulum, Mexico

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

• Dry Tortugas, Florida

• Lower Florida Keys west of the Seven Mile Bridge, Florida

Tropical Storm Watch

• Middle Florida Keys from the Seven Mile Bridge to the Channel 5 Bridge, Florida

• Flamingo to south of Englewood, Florida

• West of Indian Pass to Walton-Bay County line, Florida

Storm Surge Watch

• Indian Pass 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 possible within the watch areas in Cuba and Mexico by early Sept. 25 and the US watch areas late Sept. 25-early Sept. 26. Tropical storm conditions are expected in the warning areas in the Cayman Islands, Cuba, and Mexico Sept. 24 and are expected in the watch area in the Lower Florida Keys Sept. 25.

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 and the Cayman Islands. Amounts of 10-15 cm (4-6 inches) with isolated totals over 20 cm (8 inches) are expected over the eastern Yucatan Peninsula, Mexico. Rainfall amounts of 10-20 cm (4-8 inches) with isolated higher totals around 30 cm (12 inches) are expected over parts of the southeastern US. The heavy downpours could trigger considerable flash and urban flooding, as well as moderate-to-major riverine flooding.

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 along the eastern coast of the Yucatan Peninsula, Mexico. Peak surge could reach up to 3-4.5 meters (10-15 feet) between the Ochlockonee River and Chassahowitzka in Florida and 0.9-3 meters (3-10 feet) along other parts of the western Florida 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 Sept. 25-26. These swells are likely to cause life-threatening surf and rip current conditions.

Florida Gov. Ron DeSantis has declared a state of emergency across 41 of the state's 67 counties. Mandatory evacuation orders will come into effect in Franklin County for all barrier islands, low-lying and flood-prone areas especially along the coast and rivers, mobile homes, and RV parks from 12:00 Sept. 24 until further notice. Hamilton County has issued voluntary evacuation orders and Taylor County officials have stated they anticipate issuing a countywide mandatory evacuation order from Sept. 24. Further mandatory and voluntary evacuation orders will likely be issued across counties along the Panhandle, Tampa Bay area, and west coast of Florida as the storm approaches. Sir Captain Charles Kirkconnell International Airport (CYB) and Owen Roberts International Airport (GCM) in the Cayman Islands closed late Sept. 23 until further notice. Cruise ship arrivals at ports in Quintana Roo State, Mexico, have been canceled Sept. 24-25.

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 and render 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.