Hurricane Helene to hit Florida, Southeast with "catastrophic" impacts

Hurricane Helene is strengthening over the Gulf of Mexico's record-warm waters and speeding toward landfall Thursday evening to the south-southeast of Tallahassee as a Category 3 or higher storm.

Threat level: The large storm is forecast to bring an unprecedented 15-to-20-foot storm surge to Florida's Big Bend area. It will also bring high winds to all of Florida and plow inland with hurricane-force wind gusts likely in north Georgia, potentially including Atlanta.

• The NWS is calling the maximum storm surge forecast for the Big Bend region of Florida "catastrophic and unsurvivable." The surge may begin as early as midday.
• Flooding rains are already affecting the southern Appalachians, with rainfall totals above 15 inches expected in western North Carolina. Such rainfall amounts are likely to cause landslides and historic flooding.
• Tampa Bay is forecast to see one of its most severe storm surge events on record, with up to 8 feet of surge.

The Atlanta metro area faces one of its most significant encounters with a hurricane or tropical storm on record, with hurricane-force wind gusts anticipated.

• These winds would lead to widespread tree damage, though the exact track of the storm's core will help determine the full impacts there through Friday.

State of play: As of 11am ET, the storm was strengthening and expected to hit the Florida Big Bend coast by evening. NHC noted the storm size is at the "upper bound" of all storm sizes observed in the Gulf of Mexico.

• The storm's center was located about 255 miles southwest of Tampa and was moving northeast at 14 mph.
• Top sustained winds were at 105 mph. The NHC expects "significant additional strengthening" from this storm before landfall.

Between the lines: Helene's expansive wind field will power the potentially deadly storm surge.

• The storm's structure, with two rings of thunderstorms around the eye, has kept it from rapidly intensifying so far. But as of Thursday morning, it appeared to be intensifying faster.
• With tropical storm and hurricane warnings in effect for more than three states, power outages may encompass more than one million people by Saturday.

Zoom in: Numerous major cities, including Tallahassee, Orlando, Jacksonville and Atlanta are likely to see strong, damaging winds from this storm.

• Tallahassee may see its most damaging hurricane on record due to extremely high winds, depending on the landfall location.
• The storm will be moving at an unusually fast rate of speed at and soon after landfall, as it rotates around a weather system over the Southeast.
• This will bring the threat of significant damage, including widespread power outages, well inland through nearly the entire state of Georgia and much of South Carolina.
• NWS is warning the power outages are likely to be "prolonged" in addition to widespread.

Context: Climate change is boosting global ocean temperatures, which were at record-high levels for more than a year straight.

• According to data from the nonprofit research group Climate Central, human-caused climate change made the current record-warm waters of the Gulf of Mexico between 200 to 500 times more likely.
• The water temperature in the storm's path is extremely warm at 86°F, the NHC noted.
• There has been a documented trend toward more storms that rapidly intensify and an amplification of the intensification rates in the Atlantic as well.
• Climate change is also causing hurricanes to produce more rainfall than they did a few decades ago.

The bottom line: This storm is on track to be a multibillion-dollar disaster that reshapes coastlines and lives.

Editor's note: This story has been updated with additional developments.