SKYWARN is a program of the United States' National Weather Service (NWS). Its mission is to collect reports of localized severe weather. These reports are used to aid forecasters in issuing and verifying severe weather watches and warnings and to improve the forecasting and warning processes and the tools used to collect meteorological data. It consists of a network of severe storm spotters that observe weather conditions and make reports of severe weather to their local NWS offices. These spotters are regularly trained by personnel from the local NWS offices. In many areas, classes are conducted each spring in advance of the coming severe weather season.
Where severe storms are possible, storm spotting groups such as SKYWARN in the United States coordinate amateur radio operators and localized spotters to keep track of severe thunderstorms and tornadoes. Reports from spotters and chasers are given to the National Weather Service so that they have the information to warn the general public. Spotting provides ground information and localized conditions that the National Weather Service might not know the extent or might not otherwise be aware of. They typically report events, such as structures struck by lightning, rotating wall clouds, funnel clouds--or conditions that exceed specific thresholds, such as extremely strong winds, significant hail or very heavy rainfall. The exact reporting thresholds can vary by region and may even dynamically change during a severe weather event. Spotters also give reports during winter storms, floods, hurricanes, and wildfires.