General Severe Warnings Thresholds

• Severe Thunderstorm — Hail 1 inch or greater and/or wind gusts of 58 mph or greater.
• Heavy Rain — Rainfall rates of 1 inch per hour or greater. Often combined with thunderstorm criteria to define severe weather.
• Tornado — A tightly rotating column of air attached to a thunderstorm cloud and in contact with the ground.
• Funnel Cloud — A rotating column of air attached to a thunderstorm but not in contact with the ground. Careful observation of the surface is required, as the circulation may be invisible near the ground. Often prompts a warning.
• Flash Flood — Sudden, intense flooding of short duration (typically less than 6 hours).
• Flood / Areal Flood — Gradual flooding lasting many hours or longer, usually caused by prolonged rainfall or snowmelt and affecting rivers and streams.
• Blizzard — Sustained winds or frequent gusts of 35 mph or greater, with blowing snow and visibility less than ¼ mile for at least 3 hours.
• Snow Squall — Brief but intense snow showers producing visibility of ¼ mile or less, often accompanied by flash-freezing of road surfaces.

Wind Speed Estimation

• Less than 1 mph – Smoke rises vertically
• 1-3 MPH — Light Air Movement – Smoke drift indicates wind direction, still wind vanes
• 4-7 MPH — Light Breeze – Wind felt on face, leaves rustle, vanes begin to move
• 8-12 MPH — Leaves and small twigs constantly moving, light flags extended
• 13-18 MPH — Moderate Breeze – Dust, leaves, loose paper lifted, small branches move
• 19-24 mph – Fresh Breeze – Small trees in leaf begin to sway
• 25-31 mph – Strong Breeze – Larger tree branches moving, whistling in wires
• 32-38 mph – Near Gale – Whole trees moving, resistance felt walking against wind
• 39-46 mph – Gale – Twigs breaking off trees, generally impedes progress
• 47-54 mph – Strong Gale – Slight structural damage; shingles may lift off roofs
• 55-63 mph – Storm force – Trees broken or uprooted, considerable structural damage
• 58+ mph (60 knots) is severe threshold
• 64-72+ mph – Violent storm force – Widespread tree and structural damage

Reporting Criteria

Net Control is your guide as to what/what not to report. This depends on how deep we are into storm evolution and scope, magnitude, and the amount of traffic in the Severe Weather Room. Usually, reports are limited to NWS Severe Thresholds.

YOUR REPORT MUST INCLUDE:

• Event 'Name' (e.g., Hail, Rotating Wall Cloud, Funnel Cloud, Straight-line Wind)
• Current location
• Event Location, (advise if estimated) e.g., street/road intersections, mile markers, miles & direction from a known locality
• County in which event is located—important
• Description—brief but concise, lose adjectives whenever possible
• Clear with your callsign and wait to confirm the readback from NC.

Sometimes, criteria may be modified by NWS based on need. NWS may want hail reports to as small as 1/4″ including fall field depth, instead of the usual size of 0.75″ and larger.

What to Report to Severe Weather Net Control

Gather your thoughts. When in doubt, wait and observe for another few moments

• Tornadoes, landspouts, gustnadoes—confirm that formation is on the ground
• Funnel cloud/condensation funnel, look carefully at surface for dust/debris
• Wall Clouds may be very slowly rotating. Should be attached to cloud base in or near the clear slot, away from rain shaft. Scud—ragged clouds detached from the storm base—are tricky. If they're very near or under a wall cloud, then watch closely and we need to discuss because they may be part of a somewhat invisible, possibly weak, rotation.
• Micro & Macro (large) downbursts, look for rain/dust spreading away at surface
• Damaging straight-line winds blowing down trees and powerlines, damaging buildings (see wind speed estimation below). Handheld anemometer measurements are best.
• Hail, usually 0.75″ largest side (1″+ is severe) (see hail reporting graphic below)
• Rain Rates, 1″/hr urban, 1.5″/hr rural
• Flooding of rivers, creeks, drainages, homes, buildings, roadways

In the case of roadway flooding that is a danger to traffic, first call 911. Then, report the heads-up to Net Control, clearly stating that you have reported to 911. NC will relay the heads-up to NWS. Some NWS offices want road flooding reported only to emergency management which, in turn, relays the report to them.

• Whiteout snow conditions with visibility less than 0.5 miles

Participants are encouraged to share reports of the severity they're observing. However, exclude reports such as 'light rain' or 'it's clear here' unless called for. Always be ready to give an estimate of direction and distance of the event from your location. If you're uncertain of the severity, please state that to Net Control.

What to Report to 911

• Traffic accidents due to severe weather
• Dangerous road conditions due to severe weather, including flooding. Call 911 and report, asking them to relay to the NWS. THEN, call a heads-up to Net Control, clearly stating that you have already reported this to 911. Net Control will relay to NWS to make certain they got the message.
• Structural damage due to severe weather
• Downed power lines and poles anywhere