Garmin Flight Deck 100 用户手册

®

190-00728-04 Rev. A

366

In areas of multiple heavy cells, use the Vertical Scan feature along with antenna tilt management to

examine the areas. Remember to avoid shadowed areas behind targets.

There are no conclusive radar target return characteristics which identify a tornado. However, tornadoes

may be present if the following characteristics are observed:

• A narrow, finger-like portion 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 (numeral 9 in the southern hemisphere),

especially  if  bright  and  projecting  from  the  southwest  quadrant  (northeast  quadrant  in  the  southern
hemisphere) of a major thunderstorm.

• V-shaped notches.

• Doughnut shapes.

These shapes do not always indicate tornadoes, and tornado returns are not limited to these characteristics.

Confirmed radar observations of tornadoes most often have not shown shapes different from those of a
normal thunderstorm display.

Hail  results  from  updrafts  carrying  water  high  enough  to  freeze.    Therefore,  the  higher  the  top  of  a

thunderstorm, the greater the probability that it contains hail.  Vertically scanning the target return can 
give the radar top of a thunderstorm that contains hail. Radar top is the top of a storm cell as detected by
radar. It is not the actual top, or true top of the storm. The actual top of a storm cell is seen with the eyes
in clear air and may be much higher than the radar top. The actual top 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 characteristics similar to a very large water droplet. Because of this film of
water, and because hail stones usually are larger than water droplets, thunderstorms with large amounts 
of wet hail return stronger signals than those with rain. Some hail shafts are extremely narrow (100 yards