Ah okay, the high pressure system posted in 513?
That is the system going to keep Irma from going across the Gulf to hit TX and LA as some were suggesting it could do.
513 shows the low pressure trough moving down from the center of the US. It will provide the low pressure path of less resistance for Irma. The western high was in an earlier image. There was actually a third high pressure ridge to the NE that was in play earlier preventing northward flow. This is not a field for art majors lol.