Tropical Storm Isaac has formed in the central Atlantic, becoming the ninth named storm of the 2012 Atlantic hurricane season.

Air Force reconnaissance aircraft flew into the system Tuesday afternoon and found a small area of tropical-storm force winds associated with thunderstorms just outside the center of circulation.

However, Isaac is not yet a well-organized system, with dry air and some northeasterly wind shear limiting Isaac’s ability to rapidly organize.

Isaac will be a system to watch closely over the next week or more in the northern Caribbean and the southeastern United States. The tropical storm is expected to gather strength and become a hurricane as early as Thursday morning. Steady strengthening is forecast through late week and the system could become a hurricane as early as Thursday in the eastern Caribbean.