Spotter Information Page
Reference Information
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What makes a thunderstorm severe?
A severe thunderstorm is a thunderstorm that produces...
- wind gusts of at least 58 mph (50 knots), and/or
- hail at least 1 inch diameter (quarter size) and/or
- a tornado
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Hail Size Chart: (diameter in inches)
- Pea Size: 0.25 inches
- Small Marble: 0.50 inches
- Penny: 0.75 inches
- Nickel: 0.88 inches
- Quarter: 1.00 inches <--Any hail this size or larger is severe thunderstorm criteria
- Half Dollar: 1.25 inches
- Ping Pong Ball: 1.50
- Golf Ball: 1.75 inches
- Hen Egg: 2.00 inches
- Tennis Ball: 2.50 inches
- Baseball: 2.75 inches
- Grapefruit: 4.00 inches
- Softball: 4.50 inches
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Wind Speed Estimate:
- 25-31 mph: Large branches in motion; whistling heard in telephone wires.
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32-38 mph: Whole trees in motion; inconveniencefelt walking against the wind.
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39-54 mph: Twigs break off trees; wind generally impedes progress.
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55-72 mph: Damage to chimneys and TV antennas; pushes over shallow rooted trees.
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73-112 mph: Peels surfaces off roofs; windows broken; light mobile homes pushed or overturned; moving cars pushed off road.
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113-157 mph: Roofs torn off houses; cars lifted off ground.
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Spotter Training Classes
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Frequently Asked Questions about Spotter Training Sessions
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Do I need to preregister for these sessions? No. All you need to do is arrive at the proper time and location.
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About how long do the sessions last? Approximately 2 hours.
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Do I have to live / be a spotter in the county that I take the training session? No. The training sessions are identical.
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Below is a listing of upcoming severe weather spotter training sessions.
| There are currently no outreach events scheduled. |
