TS Helene Pushing North, Intensifying, Expanding
9/24/24 at 1 PM – This morning, Potential Tropical Cyclone 9 became Tropical Storm Helene when satellite images and Hurricane Hunter aircraft data noted a well-defined center of circulation and sustained winds of 45 MPH with higher gusts.
Helene is moving toward the northwest near 12 mph and will likely continue to do so through early Wednesday. The National Hurricane Center expects northward to north-northeastward motion at a faster forward speed on Wednesday and Thursday.
On the forecast track, the center of Helene will move across the far northwestern Caribbean Sea through tonight, and then move across the eastern Gulf of Mexico Wednesday and Thursday, potentially reaching the Gulf coast of Florida late Thursday.
Additional strengthening is forecast. Helene should become a hurricane on Wednesday and could become a major hurricane on Thursday.

A major factor in the forecast of hazards is the size of the storm. Currently, tropical-storm-force winds extend outward up to 140 miles to the east of the center. Helene’s forecast radii are at the 90th percentile of hurricane size at similar latitudes. If accurate, that means only 10% of hurricanes will exceed its size.
Due to the forecast large size of this system, storm surge, wind, and rainfall impacts will extend well away from the center, particularly on the east side.
Hazards Affecting Land
Rainfall
Heads up if you have friends, family or travel plans in the southeast this week. Helene should produce total rain accumulations of 4 to 8 inches with isolated totals around 12 inches. This rainfall will likely result in areas of considerable flash and urban flooding, with minor to moderate river flooding likely, and isolated major river flooding possible.

Flash-Flood Risk
Most of the Florida Panhandle and Georgia have a moderate (40-70%) chance of flash flooding.

Storm Surge
The combination of a dangerous storm surge and high tide will cause normally dry areas near the coast to flood. The water could reach 10-15 feet above ground between Ochlockonee River, FL and Chassahowitzka. For other areas see the map below.

Wind
Hurricane conditions are possible within the U.S. watch areas Wednesday night and early Thursday.
Tropical storm conditions should hit the Lower Florida Keys beginning Wednesday, and are possible in the watch area in the Middle Florida Keys beginning late Wednesday.
Helene should make landfall in the Panhandle Thursday morning and reach Atlanta by Thursday evening or Friday morning.

Compared to yesterday’s forecast, the chance of damaging winds now extends much farther north, well into Georgia.

The fast forward speed of the storm when it crosses the coast will likely result in inland penetration of strong winds over parts of the southeastern United States well after landfall.
Surf
Swells will spread northward toward the west coast of Florida and the northeastern Gulf Coast on Wednesday and Thursday. These swells are likely to cause life-threatening surf and rip current conditions.
Intensification
Several factors suggest rapid intensification of Helene:
- Shear over the system will decrease. Model guidance continues to show relatively low to moderate shear for the next 48 hours or so.
- Oceanic heat content values are very high.
- The system will move through an environment of upper-level divergence.
Therefore, NHC anticipates significant strengthening. NHC’s intensity forecast shows the system reaching a peak intensity around 100 kt (116 MPH) in 48 hours while over the eastern Gulf of Mexico.
Given the system’s large size, it might only weaken slowly even if it encounters sheer near the Panhandle. As a result, there is still a risk that the system could reach the coast as a major hurricane.
Key Messages
1. Helene will be near hurricane strength early Wednesday when it shoots the gap between the Yucatan and Cuba.
2. Helene should rapidly intensify over the eastern Gulf and become a major Category 3 hurricane as it approaches the coast on Thursday. The risk of life-threatening storm surge and damaging hurricane-force winds continues to increase along the coast of the Florida Panhandle and Florida’s west coast. Hurricane and Storm Surge Watches are in effect for much of that area. Residents should follow advice given by local officials.
3. Helene will bring heavy rain which will likely result in locally considerable flash and urban flooding across portions of Florida, with isolated flash and urban flooding possible across the Southeast, Southern Appalachians, and the Tennessee Valley Wednesday through Friday. Minor to isolated moderate river flooding will also be possible.
Here’s what Helene looked like this morning from space.

Posted by Bob Rehak at 1 PM on 9/24/24
2584 Days since Harvey