PRIMUSr 880 Digital Weather Radar System
ICING
DUpdrafts in a thunderstorm support abundant liquid water with relatively large droplet sizes; and when carried above the freezing level, the water becomes supercooled. When temperature in the upward current cools to about - 15 _C, much of the remaining water vapor sublimates as ice crystals; and above this level, at lower temperatures, the amount of supercooled water decreases.
DSupercooled water freezes on impact with an aircraft. Clear icing can occur at any altitude above the freezing level; but at high levels, icing from smaller droplets may be rime or mixed with rime and clear. The abundance of large, supercooled droplets makes clear icing very rapid between O _C and - 15 _C and encounters can be frequent in a cluster of cells. Thunderstorm icing can be extremely hazardous.
DRY AIR |
| MOTION OF STORM | |
|
|
| |
INFLOW |
|
|
|
|
| WARM AIR INFLOW | |
COLD | AIR | OUTFLOW |
|
| WAKE |
| WARM AIR |
| WAKE | INFLOW | |
|
|
| |
|
| COLD |
|
|
| AIR | GUST FRONT |
|
| OUTFLOW | |
NAUTICAL MILES |
|
|
|
0 | 5 | 10 | 15 |
|
|
| AD- 37561@ |
Schematic Cross Section of a Thunderstorm
Figure A- 1
Federal Aviation Administration (FAA) Advisory Circulars | A28- 1146- 102- 00 |
A- 6 |
|
