For the first time ever, the National Hurricane Center has issued warnings in advance of a tropical system being declared.
Starting this year if the confidence is high enough that a tropical cyclone will develop, watches and warnings can be issued ahead of a storm being upgraded.
In the case of Invest 92L which is approaching the Caribbean, enough confidence is there for the NHC to issue advanced warnings. Once this system makes it to the Caribbean, conditions will quickly become less favorable and any organized still will likely dissipate.
A Tropical Storm Warning is in effect for Barbados, St. Vincent and the Grenadines.