The system, located about 250 miles northeast of the Leeward Islands, is continuing to organize in favorable conditions. The NHC assigns it an 80 percent chance of development within 48 hours and a 90 percent chance within seven days, with a tropical storm likely to form as it tracks northwest then north over the southwestern Atlantic.

The tropical wave is one of three disturbances that hurricane forecasters are tracking in addition to Hurricane Erin.

Tropical Storm Erin is expected to start to gain strength starting on Wednesday and will likely become a hurricane either Thursday or Friday.