Watch This Space
It looks like Invest 91L will become Tropical Depression One of the hurricane season. There is a Hurricane Hunter mission scheduled for this afternoon, which is a pretty good indicator that the forecasters suspect that the system is on the verge of passing all the tests for official status.
The water has been warm enough to support a tropical storm, but there has been high wind shear over the area preventing development. The wind shear is lessening.
Currently the storm is forecast to head North and then Northeast. It has already produced heavy rains in Cuba and South Florida.