SKYWARN
| SKYWARN | |
|---|---|
| Run by | The National Weather Service (NWS) |
| Purpose | Reports of severe weather on the ground from trained volunteer spotters |
| Training | Free classes from local NWS offices, plus online courses |
| Who can join | Anyone who completes training; a ham license is not required |
| Amateur radio | |
| Role of hams | Weather nets that relay spotter reports to NWS offices |
| Usual frequencies | Local VHF and UHF repeaters, with simplex backup |
| Annual event | SKYWARN Recognition Day, traditionally in early December (canceled in 2025) |
| Severe thunderstorm criteria | Hail 1 inch or larger, or winds of 58 mph or more |
SKYWARN is the National Weather Service's volunteer storm spotter program. Spotters are trained to watch the sky during severe weather and report what they see, such as hail, damaging wind, flooding and tornadoes, to their local NWS office. Radar can show rotation and heavy precipitation inside a storm, but it can't see what is happening on the ground; spotter reports fill that gap and help forecasters decide when to issue, extend or cancel warnings. Anyone can become a spotter, but many SKYWARN volunteers are amateur radio operators, and ham nets are one of the main ways reports reach the weather service.
History
SKYWARN took shape in the 1960s and 1970s, as the weather service organized volunteer storm spotters in tornado-prone areas, building on local spotter networks that already existed. Hams were part of it early on: a radio operator in the field could report a tornado at once, even when a storm had knocked out the telephones. Today NWS forecast offices across the country run SKYWARN programs for their areas.
Spotter training
Spotter classes are free and are taught by meteorologists from the local NWS office, often in late winter and spring before the storm season, at libraries, fire stations and club meetings. A basic class typically lasts about two hours. It covers how thunderstorms develop, the cloud features that can come before a tornado, how to tell a real threat from harmless look-alikes, what to report and how to stay safe. Advanced classes go further into storm structure, and self-paced online courses are also available. Spotters are encouraged to repeat training every few years.
What to report
Spotters report what they observe, not forecasts or what radar apps show. Each NWS office publishes its own reporting criteria, but most ask for:
- Tornadoes, funnel clouds and rotating wall clouds. A wall cloud is a lowered area of cloud beneath a storm's base, and persistent rotation in one can come before a tornado. Training teaches spotters to tell real rotation from ragged, harmless "scud" clouds.
- Hail, with its size. Measure a stone with a ruler if possible; otherwise compare it to a familiar object.
- Strong wind, measured or estimated (many offices ask for anything of 50 mph or more), and wind damage, such as large limbs or trees down, or damage to roofs and power lines.
- Flooding, especially water over roads or entering buildings, and heavy rainfall totals.
- In winter, heavy snow and ice from freezing rain.
| Compare to | Hail diameter |
|---|---|
| Pea | 1/4 inch |
| Penny | 3/4 inch |
| Quarter | 1 inch |
| Ping-pong ball | 1 1/2 inches |
| Golf ball | 1 3/4 inches |
| Tennis ball | 2 1/2 inches |
| Baseball | 2 3/4 inches |
Hail of 1 inch, the size of a quarter, or larger, or winds of 58 mph or more, make a thunderstorm severe by the NWS definition, so reports near those thresholds are especially useful. A good report says what was seen, where (a town and intersection or a distance and direction from a known point), when, and whether it was measured or estimated.
Ham radio weather nets
When severe weather threatens, a local amateur group, often the ARES group or one working closely with it, opens a SKYWARN net, usually on a wide-coverage repeater, with a simplex frequency or a second repeater as backup. Net control takes reports from spotters in the field and at home, keeps the frequency clear, and passes reports that meet the criteria to the NWS office. Some forecast offices have an amateur station of their own, staffed by volunteer hams during severe weather, so reports go straight to a forecaster; others receive them by phone or online. Net control may also relay warnings and NWS observations back to spotters, which helps them stay in safe positions.
Spotters keep transmissions short and wait to be recognized, except for a tornado or another immediate threat to life, which takes priority.
SKYWARN Recognition Day, created by the NWS and the ARRL in 1999, is a 24-hour event traditionally held on a Saturday in early December, in which hams contact amateur stations operating from NWS offices, in thanks for the spotters' work. The NWS canceled the 2025 event, saying it lacked the time and resources to plan a national event that year, and said it would work with the ARRL and spotters to rework the spotter appreciation event for 2026.
Safety
A spotter's first job is to stay safe. Lightning is a danger in every thunderstorm, often well ahead of the heavy rain, so report from inside a vehicle or a sturdy building whenever possible. Never drive into a flooded road; a foot of moving water can carry away most cars. Mobile spotters should work in pairs, so that one person drives while the other watches the sky and works the radio, and should pull completely off the road before stopping and always keep an escape route. Spotters are not storm chasers: the aim is to watch from a safe spot, not to get as close as possible. At night, or when a tornado is hidden in rain, the right move is to take shelter like everyone else.