The National Hurricane Center has started issuing four Tropical Weather Outlooks each day May 15 through November 30. The every-six-hour updates discuss
significant areas of disturbed weather and their potential for development during the next 7 days, including a categorical forecast of the probability of tropical cyclone formation during the first 48 hours, and during the entire 7-day forecast period. The 48 h and 7-day probabilities of formation for each disturbance are given to the nearest 10% and expressed in terms of one of the following categories: low probability of development (0-30%), medium probability (40-60%), and high probability of development (70-100%). (Source)