Tropical Storm Hanna made landfall on the border of South Carolina and North Carolina this morning. Reuters reports that the storm was not quite at hurricane strength, with top windspeeds of about 60 miles per hour, but had enough force to knock power from about 10,000 homes.

Hanna, which killed more than 500 people in Haiti, will likely flood significant parts of the Eastern Seaboard as it makes its way north. At the time of this posting, its center is over southern Virginia.

Her successor, Ike, following close behind, is expected to pack an even stronger punch. Already a Category 3 hurricane in the Atlantic, current predictions by AccuWeather have Ike's eye traveling over open ocean between Cuba and Florida at the same level. However, the storm could gather strength and become a Category 4, and even a slight deviation would put the center of the storm over Havana or southern Florida. Oil rigs in the Gulf of Mexico are also at risk.

The weakest hurricanes (Category 1) bring winds of 74-to-95 miles per hour (119-to-153 kilometers per hour). Category 2 hurricanes are those with winds traveling at 96-to-110 miles per hour (154-to-177 kilometers per hour), and Category 3 storms have gales that whip around 111-to-130 miles per hour (178-to-209 miles per hour). For more detail on hurricane classifications click here.

Hurricane forecasters expect five named tropical storms -- two Category 3 hurricanes -- to touch down in the U.S. this month. We explain what makes them so destructive -- and the relationship between climate change and storm patterns in a special package.

Hanna Coastal Watches/Warnings and 5-Day Track Forecast Cone, by NOAA