Facts and limits
The facts,
and the limits.
WHIP is made to stay on the closed door through high-wind weather, and it has not been tested by a qualified engineering authority for wind speed. It is not bullet resistant and not wind rated. Further test figures appear here once EVAC supplies them; until then, this page carries the hail and storm-intensity reference the National Weather Service, NOAA and independent researchers publish, and the limits written into the license agreement.
See WHIP on a real truck: photographs from EVAC's own build.
By the size people recognize
Hail, pea to softball.
The full spotter reference, not just the four sizes most people already know. None of it is a rating for the kit. It is the same scale the Weather Service and insurers use, so a size on this page means the same thing everywhere else.
| Called | Diameter | Marks | |
|---|---|---|---|
| Pea | 1/4 in | 6 mm | |
| Marble | 1/2 in | 13 mm | |
| Penny | 3/4 in | 19 mm | |
| Nickel | 7/8 in | 22 mm | |
| Quarter | 1.00 in | 25 mm | Severe thunderstorm warning threshold |
| Half dollar | 1.25 in | 32 mm | |
| Walnut / ping-pong ball | 1.50 in | 38 mm | |
| Golf ball | 1.75 in | 44 mm | |
| Hen egg | 2.00 in | 51 mm | NWS "significant hail" threshold |
| Tennis ball | 2.50 in | 64 mm | |
| Baseball | 2.75 in | 70 mm | |
| Teacup | 3.00 in | 76 mm | |
| Grapefruit | 4.00 in | 102 mm | |
| Softball | 4.50 in | 114 mm |
How fast it actually moves
A dropped stone, not a thrown one.
Hail falls closer to its full terminal speed than most people expect, because it starts high in the storm and never slows the way rain does. NOAA's National Severe Storms Laboratory publishes three bands, by size.
Under 1 in
9-25 mph
Pea to nickel size
1 in to 1.75 in
25-40 mph
Quarter to golf ball, typical of a severe storm
2 in to 4 in
44-72 mph
Hen egg and larger, the strongest supercells
Source: NOAA National Severe Storms Laboratory, Severe Weather 101.
Storm intensity, not just stone size
The TORRO hailstorm scale.
The Tornado and Storm Research Organisation ranks a hailstorm the way the Fujita scale ranks a tornado: by the damage it actually did, from H0 (no damage) to H10. It is the closest thing hail has to a standard severity scale.
| Level | Typical stone size | What it does | |
|---|---|---|---|
| H0Hard hail | Hard hail | Up to 1/4 in | No damage. |
| H1Potentially damaging | Potentially damaging | 1/4-1/2 in | Slight damage to plants and crops. |
| H2Significant | Significant | 3/8-3/4 in | Significant damage to fruit, crops and vegetation. |
| H3Severe | Severe | 3/4-1.25 in | Glass and plastic structures damaged; paint and wood scored. |
| H4Severe | Severe | 1-1.5 in | Widespread glass damage. Vehicle bodywork damage begins here. |
| H5Destructive | Destructive | 1.25-2 in | Wholesale glass destruction, damage to tiled roofs, injury risk. |
| H6Destructive | Destructive | 1.5-2.25 in | Grounded aircraft dented, brick walls pitted. |
| H7Destructive | Destructive | 2-3 in | Severe roof damage; serious injury risk in the open. |
| H8Destructive | Destructive | 2.25-3.5 in | Severe damage to aircraft bodywork. |
| H9Super hailstorms | Super hailstorms | 3-4 in | Extensive structural damage; severe or fatal injury risk outdoors. |
| H10Super hailstorms | Super hailstorms | Over 4 in | Extensive structural damage; fatal injury risk outdoors. |
Source: TORRO, the Tornado and Storm Research Organisation.
For reference
The largest hailstone ever recovered in the United States was 8 inches across.
It fell near Vivian, South Dakota, on July 23, 2010: 8.0 inches in diameter, 18.625 inches around, and 1.9375 pounds, verified by the National Weather Service office in Aberdeen, South Dakota. It is well past H10 and outside what any spotter chart is built to describe.
The limits, stated plainly
Built for hail, debris and weather-driven projectiles. It is not bullet resistant and not wind rated. Nothing on this page, not the size chart, the fall speeds, nor the TORRO scale, is a rating for the kit. This site does not claim more than the agreement a buyer signs.
Storms don't wait.
Be ready.
Fifteen minutes on, five minutes off, and it stores in its bag. Order before the season, not during it.
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