Storm movement

I just had a quick question about some storms we have had here in the Tulsa area this July. On a couple of days storms have been moving to the West/ Northwest. Of course we all know that most storms move to the east, but what is making these storms to move to the west/northwest. Im sure it is an easy explanation. I know storms that form on boundaries can move to the west/northwest, but I dont think these storms were forming along boundaries. Any explanations would be greatly appreciated................Thanks :D
Chris - in the summertime you may have a few scenarios. For one, if it was associated with Emily last week, the storms would have moved counterclockwise around the center of circulation over Mexico, which means everything in Texas and Oklahoma would have been moving west, north, or northwest. Also, in July the plains get a lot of diurnal 'popcorn' storms that will go up as the surface becomes heated during the day and then die at night. These storms initiate in the absence of more common sources of lift such as movement of the dryline or a cold front, etc., they are located far from the jetstream, and so the midlevel steering winds are either dead or moving irratically. These storms often have motions to the north or west or northwest ... not a lot of rhyme or reason with them. In the right environment, storms also have the ability to remain stationary and propagate to the west. It's not really that rare that storms move in these directions, you just notice it more in the summer because there is nothing pushing the storms in their usual mode from west to east, etc.