Both of these images are computer model plots projecting the path of Hurricane Ike. The one on the left was from Sunday afternoon's run. Notice how most of the models have Ike moving towards either the upper Texas coast or the southern Louisiana coast.
This evening, notice how many of the same models have shifted their track further towards the south, taking it towards the lower to middle Texas coastline.
For instance, look at the blue line from day 1. This is one of the reliable models that the National Hurricane Center uses in predicting the paths of tropical systems. On Sunday, this blue line (GFDL Model) takes Ike into Morgan City, Louisiana, similar to what Gustav did. Notice this evening in later model runs how the blue line now takes Ike into the central Texas coast, near Corpus Christi.
This is a sign that the models are having a difficult time picking up on Ike and the steering currents coming into play that will ultimately dictate where the storm will head.
So what does the shift in the different forecast models mean? To be frank, not much. However, I like to look at trends. If the models tomorrow and again on Wednesday stay rather consistent, then you might be able to put some more trust in these models.
At this time, that does not mean that the upper Texas coast is spared. After all, the models tomorrow could revert back to what they showed Sunday, which would put East Texas in a risk area. Only time and consistency in the models will tell where Ike may be headed by this weekend.