The former serves civilian customers, while the latter serves the needs of the Department of Defense. At these centers, space weather is approached in much the same way as forecasting tropospheric weather. Data are collected, checked for quality, analyzed, fed into models, and displayed graphically. Forecasters mentally integrate numerical products, images, and other analyses, using experience, physical understanding, and empirical tools. A warning is given for an event that has the potential to harm satellites, equipment, and humans in near earth space environment or on the ground.
Warnings apply to phenomena that require a customer to take action in order to protect assets.
The Earth-bound analogy is a warning issued for thunderstorms, tornados, etc. The key to a warning is the ability to specify when an event will occur, how intense it will be, and how long it will last. A nowcast begins with a specification of current conditions, typically based on observations and models that assimilate data and fill the gaps, then projects those conditions into the near future. The time range for this projection is usually slightly shorter than the time required to update the observations. Nowcasts are issued on a regular basis and may include a warning if an event is in progress.