SKYWARN is a concept developed in the early 1970s that was intended to promote a cooperative effort between the National Weather Service and communities. The emphasis of the effort is often focused on the storm spotter, an individual who takes a position near their community and reports wind gusts, hail size, rainfall, and cloud formations that could signal a developing tornado. Another part of SKYWARN is the receipt and effective distribution of National Weather Service information.
The organization of spotters and the distribution of warning information may lies with the National Weather Service or with an emergency management agency within the community. This agency could be a police or fire department, or often is an emergency management/service group. This varies across the country however, with local national weather service offices taking the lead in some locations, while emergency management takes the lead in other areas.
People have organized SKYWARN groups that work independent of a parent government agency and feed valuable information to the National Weather Service. While this provides the radar meteorologist with much needed input, the circuit is not complete if the information does not reach those who can activate sirens or local broadcast systems.
SKYWARN spotters are not by definition "Storm Chasers". While their functions and methods are similar, the spotter stays close to home and usually has ties to a local agency. Storm chasers often cover hundreds of miles a day. The term Storm Chaser covers a wide variety of people. Some are meteorologists doing specific research or are gathering basic information for training and comparison to radar data. Others chase storms to provide live information for the media, and others simply do it for the thrill.
Storm Spotting and Storm Chasing is dangerous and should not be done without proper training, experience and equipment.
The National Weather Service conducts spotter training classes across the United States, and your local National Weather Service office should be consulted as to when the next class will be held.
SKYWARN Reporting Criteria
The following is a reporting criteria that should be used to report to Net Control
Tornadoes or funnel clouds (be very wary of look-alikes; watch for rotation)
Wall clouds, especially if they are rotating
Hail (Be specific with regard to size; DO NOT report MARBLE size, see below)
Winds (40 mph or greater; specify whether estimated or recorded)
Very large branches downed
Trees/power lines downed
Structural damage to buildings (roof, windows, etc.)
Flooding
PROCEDURES
1) Advise Net Control Operators BRIEFLY WHAT you observed; and WHEN & WHERE it was observed.
2) Make sure hail size is noted using chart below (NO Marble Sized Hail)
3) Make sure if winds are estimated that you use the chart
Estimating Hail Size
Pea Size 1/4"
Dime Size 3/4"
Quarter Size 1"
Half Dollar 1-1/4"
Golf Ball 1-3/4"
Baseball 2-3/4"
Estimating Wind Speeds (miles per hour)
0: Smoke rises vertically
1-3: Direction of wind shown by smoke drift but not wind vanes
4-7: Wind felt on face, leaves rustle, ordinary wind vane moved by wind
8-12: Leaves and small twigs in motion, light flags extended
13-18: Dust raised, loose paper raised, small branches move
19-24: Small leafy trees sway, crested wavelets form on lakes and ponds
25-31: Large branches in motion, whistling in telephone wires and chain link fences
32-38: Whole trees in motion, inconvenience felt walking against wind
39-54: Twigs break off trees; wind generally impedes progress
55-72: Damage to chimneys and TV antenna; pushes over shallow rooted trees
73-112: Peels surface off roofs; windows broken; light trailer houses pushed or overturned; moving automobiles pushed off roads
113-157: Roofs torn off houses; weak buildings and trailer houses destroyed; large trees snapped and uprooted
158 & up: Severe damage; cars lifted off ground