4-73190-01102-02 Rev. B Garmin G500 Pilot’s GuideForewordSec 1SystemSec 2PFDSec 3MFDSec 4HazardAvoidanceSec 5AdditionalFeaturesSec 6Annun.& AlertsSec 7SymbolsSec 8Glossary Appendix AAppendix BIndex4.8.5.3 TornadoesThere is no conclusive radar target return characteristics which will identifya tornado, however, tornadoes may be present if the following characteristicsare observed:• A narrow, finger-like portion, as shown on the previous page, extends and,in a short time, curls into a hook and closes on itself.• A “hook” which may be in the general shape of the numeral “6,” especiallyif bright and projecting from the southwest quadrant (northeast quadrantin the southern hemisphere) of a major thunderstorm.• V- shaped notches.• Doughnut shapes.These shapes do not always indicate tornadoes, nor are tornado returnslimited to these characteristics. Confirmed radar observations of tornadoesmost often have not shown shapes different from those of a normal thunder-storm display.4.8.5.4 HailHail results from updrafts carrying water high enough to freeze. Therefore,the higher the top of a thunderstorm, the greater the probability that it containshail. Vertically scanning the target return can give the radar top of a thunderstormthat contains hail. Radar top is the top of a storm cellas detected by radar. It isnot the actual top, or true top of the storm. The actual top of a storm cell is seenwith the eyes in clear air and may be much higher than the radar top. The actualtop does not indicate the top of the hazardous area.Hail can fall below the minimum reflectivity threshold for radar detection.It can have a film of water on its surface, making its reflective characteristicssimilar to a very large water droplet. Because of this film of water, and becausehail stones usually are larger than water droplets, thunderstorms with largeamounts of wet hail return stronger signals than those with rain. Some hailshafts are extremely narrow (100 yards or less) and make poor radar targets. Inthe upper regions of a cell where ice particles are “dry” (no liquid coating), targetreturns are less intense.Hail shafts are associated with the same radar target return characteristicsas tornados. U-shaped cloud edges 3 to 7 miles across can also indicate hail.
