SKYWARN and SKYWARN Nets

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 “ground truth” 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. Not all spotters are amateur radio operators, Non-Hams are encouraged to participate in SKYWARN Net activities via the GroupMe App. Amateur operators should monitor the repeaters shown below when observing or expecting severe weather.

  • SKYWARN Net Operations Guide click here.
  • MICON-DTX Manual download here.
  • SCC ARPSC MICON Liaison Procedures click here.
  • GroupMe App and GroupMe SKYWARNProcedures can be found here.
  • GroupMe App SKYWARN NET Script Here

Amateur radio operators have been the mainstay of the SKYWARN program since its inception. This is largely due to their ability to communicate by radio even when power outages occur and internet/cell service is interrupted. In St Clair County, the SKYWARN Net is activated by either the county’s Homeland Security Division directly to ARES/SKYWARN Leadership or, most often, thru the WINS System triggered by a County/NWS informed criteria.

Due to the large distances covered by the St Clair County SKYWARN Net (over 40 miles between Harsens Island and Yale), several repeaters are linked during nets in Condition Green or higher. When the NWS or SCC EMD requests Net Control Stations to go to Standby or Pre-Net condition, the 146.720 AA8K repeater (located in Port Huron Twp) is used. The latest weather info will be available on this repeater. If there is an escalation of the severe weather threat, additional repeaters may be linked in to provide county-wide coverage. Those repeaters that may be linked are listed below. There is a slight send/rec delay when the repeaters are linked. Wait an extra few seconds for locations to synchronize before speaking.

More information can be found at the National Weather Service.

Frequencies Used

  • 146.720 MHz – ( 131.8 Hz tone) SKYWARN Net in Standby
  • 147.300 MHz – (192.8 Hz tone)
  • 146.800 MHz – (100 Hz tone)
  • 147.320 MHz + (169.7 Hz tone)
  • 444.900 MHz + (131.8 Hz tone) Linking Repeater

Skywarn Net Forms

SKYWARN Activation Criteria

SKYWARN operations are activated when the National Weather Service issues a Watch or Warning indicating a threat to our county. When a Watch or Warning is issued, the St Clair County WINS System will initiate Text, Email or Phone messages to Leadership, Net Control Stations and Spotters registered in SCC. The nature of the threat and degree of response requested will be indicated. Watches and Warnings in adjacent counties can affect the existence and subsequent level of our local SKYWARN Net. Spotters should take actions appropriate to their situation. Hams will check in to the net via a local radio repeater. Non-Hams can check in via GroupMe.

ARES/NWS trained Net Control Stations initiate a SKYWARN Net with individual operators checking in from various locations throughout the county. Severe weather reports from the spotters are radioed to the net control station and are relayed to the NWS office in White Lake using various communication methods. These include reports to White Lake NWS via packet text, telephone or vhf/uhf using MICON Key Stations.

In some cases the net will be operated from the county’s Emergency Operations Center. Although, most often the Net Control Station will operate from his/her home shack and coordinate activities from there. SKYWARN and HS/EM personnel communicate on MPSCS radio circuits during severe weather events.

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

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.

Useful Information for Skywarn

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 (MPH)

  • 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.

Skywarn Net Expansion

The most likely use of the SCC ARES capabilities is the expansion after a severe storm. Weather nets are easily transitioned into an ARES/RACES configuration to assist local agencies in reporting damage and manning shelters. In addition to assisting the NWS, the ARES works closely with the county’s Homeland Security Division by providing information on situations such as flooding, storm damage and damage to power and communication utilities. This information is useful in providing a quick assessment of the magnitude of an event and arranging assistance to local municipalities when their resources may become overwhelmed.