Estimating Reports

Measured reports are much more desirable than estimated reports. They are generally much more accurate. Sometimes it’s hard to estimate properly under severe weather conditions. Over-estimating is as bad or worse than under-estimating storm criteria.

If you must estimate, here are some handy guidelines:

Hail Size

Pea Size 1/4″
Dime Size 1/2″ (Minimum reportable size)
Penny Size 3/4″
Nickel Size 1″
Golf Ball Size 1-3/4″ (Fore!)
Baseball Size 2-3/4″ (Get out the glove and your helmet!)

Rainfall Intensity

Light Less than 0.2″/Hr.
Moderate 0.2″ to 1.0″/Hr.
Heavy 1.1″ to 2.2″/Hr. (Minimum reportable rain)
Very heavy 2.3″ to 4.5″/Hr.
Intense 4.6″ to 7.1″/Hr.
Extreme More than 7.1″/Hr. (Anybody know how to build an arc?)

Wind Speed (Miles Per Hour)

0 Smoke rises vertically
1-3 Smoke drifts but windvanes do not move
4-7 Wind felt on face, leaves rustle
8-12 Small twigs in motion
13-18 Dust raised, loose paper raised, small branches move
19-24 Small leafy trees move, crested wavelets form on water
25-31 Large branches in motion, whistling in wires
32-38 Whole trees in motion, inconvenience felt walking against wind
39-54 Twigs break off trees
55-72 Damage to chimneys, pushes over shallow rooted trees
72-112 Peels surface off roofs, windows broken, trailer homes overturned
113-157 Roofs torn off houses, trailers destroyed, large trees snapped and uprooted
158 & Up Severe damage, cars lifted off ground (life passes before your eyes)