Storm chasing is broadly defined as the pursuit of any severe weather condition, regardless of motive. A person who chases storms is known as a storm chaser, or simply a chaser. While witnessing a tornado is the single biggest objective for most chasers, many chase thunderstorms and delight in seeing cumulonimbus structure, watching a barrage of hail and lightning, and seeing what skyscapes unfold. There are also a smaller number of storm chasers who chase hurricanes.
Storm chasers are not paid to chase, with the exception of television media crews in certain television markets, video stringers and photographers, and a handful of graduate meteorologists and professors. A few entrepreneurs, however, manage to sell storm videos and pictures or operate "chase tour" services. Financial returns are relatively meager given the expenses with most chasers spending more than they take in. No degree or certification is required to be a storm chaser. The National Weather Service does conduct severe weather workshops and storm spotter training, usually early in the spring.
The term "storm chaser" is also loosely applied to any of the support personnel (insurance staff, contractors, etc.) brought in to clean up after large storms.
In 1972 the University of Oklahoma in cooperation with the National Severe Storms Laboratory began the Tornado Intercept Project. This was the first large-scale chase activity sponsored by an institution. It culminated in a brilliant success in 1973, with the Union City, Oklahoma tornado providing a foundation for tornado morphology. The project produced the first legion of veteran storm chasers, with Hoadley's Storm Track magazine bringing the community together in 1977.
Storm chasing then reached popular culture in three major spurts: in 1978 with the broadcast of a segment on the television program In Search of...; in 1985 with a documentary on the PBS series Nova; and in May 1996 with the theatrical release of Twister which provided an action-packed but comically distorted glimpse at the hobby. Further early exposure to storm chasing encouraging some in the weather community resulted from several articles beginning in the late 1970s in Weatherwise magazine. Various television programs, increased coverage of severe weather by the media, and especially the Internet have also contributed to a significant growth of storm chasing since the mid-late 1990s. A sharp increase in the general public impulsively wandering in their local area searching for tornadoes similarly is largely attributable to these factors.
The most significant hazard actually is driving, which, in itself, is a statistically dangerous activity that is exacerbated by the severe weather. Adding still more to this hazard are the copious distractions that can be vying for a chasers' attention such as driving, communicating to chase partners and to others with a phone and/or radio, navigating, watching the sky, checking weather data, and shooting photos or video. Again here, prudence is paramount in minimizing the risk. Chasers ideally work to prevent the driver from multi-tasking either with chase partners covering the other aspects or with the driver pulling over to do these other things if he/she is chasing alone.
Chasers may operate whenever significant thunderstorm activity is occurring; whatever the date. This most commonly includes more sporadic activity occurring in warmer months of the year bounding the spring maximum, such as the active month of April; and farther north especially, the summer months. An annually inconsistent and substantially smaller peak of severe thunderstorm and tornado activity also arises in the transitional months of autumn, particularly October and November.
Some organized chasing efforts have also begun in the Top End of the Northern Territory and in southeast Australia, with the biggest successes in November and December. A handful of individuals are also known to be chasing in other countries, including Israel, Italy, Spain, France, Belgium, Germany, Finland, the Netherlands, Switzerland and New Zealand; although many people trek to the Great Plains of North America from these and other countries around the world (especially from the United Kingdom).
Historically, storm chasing relied on either in field analysis or in some cases now-casts from trained observers. The first in-field technology consisted of radio gear for communication. Much of this equipment could also be adapted to receive radiofax data which was useful for receiving basic observational and analysis data. The primary users of such technology were university research groups who often had larger budgets than individual chasers.
Radio scanners were also heavily used to listen in on emergency services and storm spotters so as to determine where the most active or dangerous weather was located. A number of chasers were also radio amateurs, and used mobile (or portable) amateur radio to communicate directly with spotters and other chasers, allowing them to keep abreast of what they could not themselves see.
It was not until the mid to late 1980s that the evolution of the laptop computer would begin to revolutionize storm chasing. Early on, some chasers carried acoustic couplers to download batches of raw surface and upper air data from payphones. The technology was too slow for graphical imagery such as radar and satellite data; and during the first years this wasn't available on any connection over telephone lines, anyway.
Most meteorological data was acquired all at once early in the morning, and the rest of day's chasing was based on analysis and forecast gleaned from this; as well as on visual clues that presented themselves in the field. Occasionally chasers would make stops at rural airstrips or NWS offices for an update on weather conditions. NOAA weather radio could provide information in the vehicle, without stopping, such as weather watches and warnings, surface weather conditions, convective outlooks, and NWS radar updates. Nowadays, storm chasers may use high-speed internet access available in any library, even in the smallest towns in the US. This data is available throughout the day, but one must find and stop at a location offering Internet access.
With the development of the mobile computers, the first in computer mapping software was made available, at about the same time the VHS camcorder began to grow in popularity rapidly. Prior to the mid to late 1980s most motion picture equipment consisted of 8 mm film cameras. While the quality of the first VHS consumer cameras was quite poor (and the size somewhat cumbersome) when compared to traditional film formats, the amount of video which could be shot with a minimal amount of resources was much greater than any film format at the time.
The 1990s marked the first technological leaps and bounds. With the quick development of solid state technology, television sets for example could be installed in most vehicles with ease allowing storm chasers to actively view local TV stations. Mobile phones became popular making group coordination easier when traditional radio communications methods were not adequate. The development of the public internet in 1993 allowed FTP access to some of the first university weather sites.
The mid 1990's marked the development of smaller more efficient marine radars. While such marine radars are illegal if used in land-mobile situations, a number of chasers were quick to adopt them in an effort to have mobile radar. These radars have been found to interfere with research radars, such as the Doppler On Wheels utilized in field projects. The first personal lightning detection and mapping devices also became available and the first online radar data was offered by private corporations often with a delay for free services.
2001 marked the next great technological leap for storm chasers as the first Wi-Fi units began to emerge offering wireless broadband service in many cases for free. In 2002, the first Windows-based package to combine GPS positioning and doppler radar appeared called SWIFT WX SWIFT WX allowed storm chasers to accurately position themselves relative to tornadic storms while mobile.
In 2004, two more storm chaser tools emerged. The first was a new XM Satellite Radio based system utilizing a special receiver and Baron Systems weather software. Unlike pre-existing cellular-based services there was no risk of dead spots, and that meant that even in the most remote areas storm chasers still had a live data feed. The second tool was a new piece of software called GRLevel3 GRLevel3 utilized both free and subscription based raw weather radar files; displaying the data in a true vector format.
The most common chaser communications device is the cellular phone. These are used for both voice and data connections. It is not uncommon that chasers travel in small groups of cars, and may use Citizen Band radios (declining in use) or inexpensive GMRS / FRS hand-held transceivers for inter-car communication. More commonly, many chasers are also amateur radio operators and use the 2 meters VHF and, less often, 70 cm UHF bands to communicate between vehicles or with SKYWARN spotter networks. Scanners are often used to monitor spotter and sometimes public safety communications.
In-field environmental data is still popular among some storm chasers, especially temperature, moisture, and wind speed data. Many have chosen to mount weather stations atop their vehicles.
Chasers have heavily utilized still photography since the beginning. Videography gained prominence by the 1990s into the early 2000s but a resurgence of photography has occurred with the advent of affordable and versatile digital SLR cameras. Prior to this, 35 mm print and slide film formats were mostly used, along with some medium format cameras.