Understanding how storms form helps explain why forecasters watch ocean temperatures and wind patterns so closely.

Invest 94L became Potential Tropical Cyclone Nine and will be named Imelda when it becomes a hurricane. If Imelda and Hurricane Humberto get close enough, they may pinwheel around a common point in a phenomenon known as the Fujiwhara Effect, which will send Imelda out to sea.

As it turns out, the hurricane naming system is an organized, multistep global process—not someone randomly selecting names for storms as they form. It involves an element of mystery and difficult decisions made on an annual basis.

Imelda is not expected to directly strike the U.S., but could bring rain and rough surf to the Palmetto State.

Tropical Depression Nine formed late Saturday morning over the southeastern Bahamas and is forecast to steadily strengthen into Hurricane Imelda by early next week as it approaches the coast of South Carolina.

Although no immediate land threat exists from either Gabrielle or the forming Humberto, the increase in tropical activity underscores how quickly conditions in the Atlantic basin can change. September is historically the most active month of the hurricane season, which officially runs through November 30.

Humberto is expected to bypass the Greater Antilles before turning into the Atlantic. But interaction with another tropical system could change that.