The American forecast model (GFS) predicts Joaquin will veer northwestward, ramming into Virginia, Maryland or North Carolina this weekend. The European forecast model suggests Joaquin will avoid the East Coast entirely. And the National Hurricane Center forecast offers somewhat of a compromise between the two.
Why are they different? This is interesting.
The GFS model is done by the US government, it is free, and comes out four times a day. The European hurricane model is private, released twice a day and costs $$. The European model has generally been more accurate since the 1980s.
Why? Super computer power! It is much more accurate, much stronger and a has much better computing power.