The Skywarn program was developed by the National Weather Service (NWS) in 1971 for the purpose of fielding a network of trained weather spotters. These spotters provide real time observations of actual weather conditions at their location. This information is used by the NWS to issue highly accurate severe weather forecasts and warnings. In addition to improving warning capabilities, the information gathered by Skywarn spotters is also used by the NWS to validate the radar images generated by the NWS.

Amateur radios operators have been a mainstay of the Skywarn program since its inception. This is largely due to its ability to communicate by radio even when power outages occur and telephone service is interrupted. In Oakland County, the ARPSC is activated by the County's Homeland Security Division. ARPSC personnel initiate a Skywarn net with individual operators checking in to the net from various locations throughout the County. Severe weather reports from the spotters are radioed to the net control station where they are relayed by radio to the NWS office in White Lake.

In addition to assisting the NWS, the ARPSC works closely with the County's Homeland Security Division by providing information on such items as flooding, storm damage and damage to power and communication utilities. This information is useful in providing a quick summary of the magnitude of an event and arranging assistance to local municipalities when their resources may become overwhelmed.

More information can be found at the National Weather Service.

Skywarn Activation Criteria

Skywarn operations are activated when the National Weather Service issues one of the following Watches or Warnings. When a Watch or Warning is issued, the Homeland Security On-Call individual will contact a member of the command staff to notify them of the event and request a Skywarn Net. In most cases the net will be operated from the County's Emergency Operations Center. In some cases a severe storm may suddenly form and prompt an NWS Warning. In the case of 'pop-up' storms, a net will be conducted from the net control operator's home since the event will typically finish before an operator could arrive at the EOC.

Severe Thunderstorm Watch

A Severe Thunderstorm Watch is issued when severe thunderstorms are possible in and near the watch area. It does not mean that they will occur. It only means they are possible.

Severe Thunderstorm Warning

A Severe Thunderstorm Warning is issued when severe thunderstorms are occurring or imminent in the warning area. Storms become severe when wind speeds reach 58 mph or higher AND/OR there is hail 1 inch in diameter or larger.

Tornado Watch

A Tornado Watch is issued when severe thunderstorms and tornadoes are possible in and near the watch area. It does not mean that they will occur. It only means they are possible.

Tornado Warning

A Tornado Warning is issued when a tornado is is visually detected or indicated by radar. When a tornado warning is issued, seek safe shelter immediately.

Please note that the County's Outdoor Early Warning sirens are activated if a Tornado Warning is issued by the National Weather Service or Wind speeds in a Severe Thunderstorm reach 70 mph or above.


Estimating Hail Size:

  • Pea size: 1/4" diameter
  • Marble size: 1/2" diameter
  • Quarter size: 1" diameter
  • Golf ball size: 1 3/4" diameter
  • Baseball size: 2 3/4" diameter

Estimating Wind Speed (Miles Per Hour)

  • 25-31 Large branches in motion; whistling telephone lines
  • 32-38 Whole trees in motion; inconvenience felt walking against wind
  • 39-54 Twigs break of trees; wind generally impedes progress.
  • 55-72 Damage to chimneys and TV antennas; wind pushes over shallow rooted trees.
  • 73-113 Wind peels surface off roofs; windows broken; mobile trailers pushed or overturned; moving automobiles pushed off roads.
  • 113-157 Roofs torn off houses; weak buildings and mobile homes destroyed; large trees snapped and uprooted,
  • 158+ Severe damage. Cars lifted off the ground.