Image by NOAA
The National Hurricane Center has said it will issue watches and warnings for tropical storms and hurricanes some 12 hours earlier, thanks to better forecasts.
Presently they're issued 36 hours prior to storm arrival.
Here's details from the press release:
NOAA’s National Hurricane Center in Miami will issue watches and warnings for tropical storms and hurricanes along threatened coastal areas 12 hours earlier than in previous years. According to NHC experts, advancements in track forecasts are making it possible for forecasters to provide greater lead time.
Tropical storm watches will be issued when tropical storm conditions are possible along the coast within 48 hours. Tropical storm warnings will be issued when those conditions are expected within 36 hours. This is an increase of 12 hours from those issued in previous years.