How do I regognize a ULL? ie. I am looking at water vapor images of what was/us invest92L, I see a clear area to the east, which the images seem to be wrapping around, yet I believe it was mentioned that the ULL that would affect this system had moved into the GOM. Is there another map I should be watching? How do I know what I am looking at is the ULL? Do the low pressure systems push or pull a wave? I can recognize the high pressure ridge to the north in the Atlantic. More importantly, is there a site where I can begin to understand this information. Thanks