The key to the forecast for Helene is a small 300 MB upper-level low-pressure system on the Yucatan Peninsula. This feature is not being forecasted very well by the models because the orientation of the models would suggest the winds are from the southeast when, in reality, the winds are from the southwest. The vertical wind shear from the southwest is producing a low-pressure structure skewed to the northeast with a surface low-pressure system in the western Caribbean Sea. I don’t see this vertical wind shear changing all that much over the next 48 hours, and there is no sign of the convection wrapping around either center.
However, the atmospheric environment will gradually improve, and Helen will gradually intensify between the Yucatan Peninsula and Cuba. With the very warm waters in the eastern Gulf of Mexico, Helene will have the potential to strengthen into a hurricane. If the vertical wind shear subsides enough, Helene could become a major hurricane while approaching the Florida coast on Thursday. Helene is a large storm for this latitude and is expected to grow in size while approaching the Florida coast, which will make impacts from this storm far reaching into much of the Southeastern United States, including heavy rain and strong wind in Alabama, Georgia, and South Carolina.
The synoptic model guidance is in strong agreement with the development of an upper-level low-pressure system in the Mississippi River Valley, which would force Helene to lift northward towards the eastern Gulf Coast by Thursday night.