I just sailed there in a sloop, and I've concluded that the area around F15 is bugged/glitched.
Shows over guys, there's nothing to see.
Here is a video of me loading into a fresh game and sailing toward F15 from Golden Sands from beginning to end.
When I got there, my ship started behaving as if it were in the storm, but the storm wasn't even in the area. There was no rain, but I was getting lightning, holes in my hull, wheelspin, and high waves in calm water.
You can see water clipping about the ship throughout the video.
F15 may be glitched such that everyone's going to get a different type of bug depending on rngesus.
There's nothing elusive or mysterious going on here.