Hurricane Helene is steadily intensifying this evening, although the core is trying to clear some dry air influence from the Yucatan Peninsula. Helene is now lifting into the eastern Gulf of Mexico and will continue to move into an improving atmospheric environment.
Helene will fall under the influence of a developing upper-level low-pressure system in the Mississippi River Valley and an upper-level ridge over the Southeastern United States, forcing Helene to quickly move to the north-northeast towards the Florida Panhandle by tomorrow night. Between the upper-level low-pressure system and the upper-level ridge, the atmosphere will support an enhanced divergence at 250 MB, enhancing the rising motion of the warm-core low-pressure system. This environment, combined with very warm waters in the eastern Gulf of Mexico, no wind shear, and very little dry air will increase the potential for rapid intensification of Helene into a major hurricane. Aside from an eyewall replacement cycle or some mid-level dry air that is currently not seen in the guidance, there isn’t much to stop Helene from becoming a major hurricane with significant impacts on the Florida Panhandle. In addition to the intensification, the speed of the storm will enhance sustained winds on the eastern side of the storm, possibly adding 10 to 20 mph winds on top of the observed sustained winds in the eyewall.
The interaction of the upper-level low-pressure system will create another unique dynamic to this storm threat for the rest of the Southeastern United States from the Gulf Coast to the Tennessee River Valley. When an upper-level low-pressure system (cold core) interacts and absorbs a hurricane, the surface low-pressure system rapidly transitions into an extratropical storm with the rain shield expanding and the wind field expanding while core winds subside. So, instead of 115 mph wind, the storm features 50 mph sustained wind but over a 40 mile radius rather than a 10 mile radius. Any way you slice it, this storm will have significant and lasting impacts on the Southeast.