Did you see the wicked turn North in Tropical Storm Hanna? Check out the two links below, one is a radar loop of the storm and the other is the historical track of the storm.
http://www.wunderground.com/tropical/tracking/at200808_radar.html#a_topad (might take a few seconds to load the loop)
In the historical track of the storm, you can see how the storm was heading right for Florida, and just made a hard turn to the right and is heading North. What caused that was in part a huge area of high pressure. You can see in the chart below a large "H" in the Atlantic, with winds circulating in such a way that it will steer Hanna North. Then, Hanna gets caught in the "Westerlies" and zooms quickly to the Northest across the US East coast.
Hanna is a tropical storm now and is expected to make landfall late Friday night near Wilmington, North Carolina as a strong tropical storm with sustained winds near 70mph.
To track Hanna and other stroms like Hurricane Ike and Tropical Storm Josephine click on this link.