Here are some facts you may already know, a few that you probably didn’t, and one or two that, properly applied, might keep you from getting killed.
THE ENEMY’S SECRETS:
- Hail is generally found at about the 10,000 to 15,000 foot levels above the terrain, with the greatest frequency of hail occurring at the mature stage of the thunderstorm.
- Hail doesn’t fall at the same density as heavy rain, so the clouds can look deceptively bright. Bases may also be deceptively high.
- The clouds themselves will often have streamers — internally. Translation: Unlike virga, those streamers will not extend below the cloud base to give the precipitation away!
- Hail may be encountered in clear air when simply flying in the vicinity of a thunderstorm. Winds may carry hail miles away, so give those clouds a wide berth (especially if they look bluish-green!) Again, this can be miles from the parent thunderstorm. Consider that a severe storm may have a potential 20 mile “hailing range”.
- It only takes seconds for hail to cause serious structural damage to an aircraft — especially if the hail is three-fourths of an inch or greater. (If you’re lucky, circumstances will not afford you the opportunity to measure hail while flying through it.)
- If you should encounter hail, do NOT attempt to turn away. Encounters with hail are usually of short duration — generally, the quickest way out is straight on. Grit your teeth and lean into it. If you haplessly blunder into a hailshaft, a column of hail falling from a single thunderstorm cell which typically moves at speeds between 25 and 50 knots (and probably in a direction different from your own), it won’t last long. They’re usually narrow, from less than 100 feet wide, on up to 2 miles in width. (The ground track of a hailshaft is called a hailstreak.)
- The combination of all the individual hailstreaks of a storm are known as a hailswath. An unusually large ‘super-hailstreak’ in Illinois in 1968 had a maximum width of 19 miles and a length of 51 miles. It lasted for 90 minutes, the larger stones were 2 1/4 inches in diameter, and the total production was 82 million cubic feet of ice. (That’s like an ice-cube almost 435 feet high.)
- The presence of large hail indicates very strong updrafts and downdrafts within the thunderstorm. It takes updrafts of at least 55 mph to support golf ball sized hail, and at least 90 mph for hail the size of baseballs. (However, since hailstones aren’t always spherical, their drag and therefore the strength of the updraft needed to continue the accretion process may vary.)
- Stormscopes may not show the presence of hail. That includes flying on top and behind the thunderstorm, and when flying underneath the anvil. (Some weather radar can — the WSR-88D Doppler Radar can look inside a thunderstorm and estimate hail size based on the amount of energy reflected back.)
- The largest numbers of hailstones that move at high velocity are naturally found inside the thunderstorm itself. Smaller hail makes up most of a hailstorm. Large hail falls only in a small region of the total storm.
HAIL NOTES FOR THE GROUNDBOUND
Tornadoes are often preceded by very large hail. (Often large hail is observed immediately northward of a tornado track, but the presence of hail doesn’t always foretell a tornado and the absence of hail doesn’t always mean there isn’t a risk of tornadoes.) When accompanied by a tornado watch or warning, hail can be an indication that a tornado is imminent. And last, from the Guinness Department: The largest hailstone ever recorded fell in Coffeyville, Kansas on September 3, 1970. It measured about 17.5 inches in circumference (over 5.6 inches in diameter) and weighed more than 26 ounces (over 11/2 pounds)!
HAIL & INSURANCE
As far as your insurance company is concerned, there are two kinds of hailstorm damage. The first is actual physical breakage (cracked windscreens, or surfaces damaged so severely as to affect airworthiness). The second, however, is cosmetic: namely, the dimples where the hailstones hit. The aircraft can still be airworthy and fly just as well as before. (I don’t think ‘the golf ball look‘ would make for a popular speed mod, though.) In the first case, the insurance company is obligated to pay for repair or replacement. (They might want to verify that you didn’t deliberately fly in harm’s way.) In the second case, your dimpled pride and joy now has a reduced resale or trade-in value, which might involve negotiation between you and the insurance adjuster for example, compensating you for an agreed upon amount of depreciation. (If re-skinning is even an option, repairs can be interminably slow, and the log book will be festooned with records of the work performed, which can reduce the value almost to the same extent as the original damage.)
DEFENSE: RUN AWAY
Unless you’re wearing airline epaulets or you’re flying under a canopy for Uncle Sam, you may never feel any obligation to face down hostile weather. When you see the threat of hail — either visually or through a weather briefing, stay away… far away.
BOTTOM LINE: On May 8, 1998, AirTran captain Benton West was flying through a storm en route from Atlanta to Chicago when, somewhere around Chattanooga Tennessee, someone opened fire. Hail smashed the cockpit window of his DC-9 and blasted the airliner’s nose cone clean off. Passengers and luggage tumbled about the cabin as the stricken airliner suddenly dropped more than 1,000 feet. Imagine what that would’ve done to a Malibu, an Aerostar, or your Skyhawk. ‘Nuff said.