The primary purpose of WeatherStar units is to disseminate weather information for local forecast segments on The Weather Channel. The forecast and observation data – which is compiled from the National Weather Service, the Storm Prediction Center and The Weather Channel itself (which began providing forecasts for TWC in 2002 that replaced the National Weather Service's zone forecasts used in the STAR's descriptive forecast product) – is received from the vertical blanking interval of the TWC video feed and from data transmitted via satellite; the localized data is then sent to the unit that inserts the data and accompanying programmed graphics over the TWC feed. The WeatherStar systems are typically programmed to cue the local forecast segments and Lower Display Line at given times. The units are programmed to feature customized segments known as "flavors," which are pre-determined variables in the products displayed during each local forecast segment; this allows certain types of products to be added or removed from the segment depending on the time of broadcast (with the extended forecast usually being exempted from removal), and also allows the reduction or extension of the segment lengths. Flavor lengths previously varied commonly between 30 seconds and two minutes, with some running as long as six minutes during the late 1980s and the mid-1990s; in April 2013, the length of these flavors was changed to a uniform one-minute span.