Obscurations
Obscurations aloft that cover 1/8 or more of the sky need to be reported in the sky condition. Obscurations include haze, dust, smoke, and volcanic ash. Liquid or frozen water particles whether in cloud or precipitation form are reported separately. Precipitation falling from a cloud but not reaching the surface (referred to as virga) is considered part of the cloud from which it is falling.
| Obscuration | Code/Abbreviation | Weather Symbol |
|---|---|---|
| Hydrometeors – Precipitation | ||
| Drizzle | DZ |  |
| Freezing Drizzle | FZDZ |  |
| Hail | GR |  |
| Ice Crystals | IC |  |
| Ice Pellets | PE |  |
| Ice Pellet Showers | SHPE |  |
| Rain | RA |  |
| Freezing Rain | FZRA |  |
| Rain Showers | SHRA |  |
| Snow | SN |  |
| Snow Pellets | GS | |
| Snow Grains | SG |  |
| Snow Showers | SHSN |  |
| Hydrometeors – Non-precipitation | ||
| Blowing Snow | BLSN |  |
| Blowing Spray | BLPY |  |
| Fog | FG |  |
| Shallow Fog | MIFG |  |
| Partial Fog | PRFG |  |
| Patches of Fog | BCFG |  |
| Freezing Fog | FZFG |  |
| Lithometeors | ||
| Dust | DU |  |
| Blowing Dust | BLDU | |
| Haze | HZ |  |
| Sand | SA | |
| Blowing Sand | BLSA | |
| Smoke | FU |  |
| Volcanic Ash | VA | none |
What type of obscuration is present in this image apart from the low clouds? Choose the best answer.
The correct answer is a).
The rising clouds in the background of the image make up the volcanic ash plume of the Okmok volcano. It will need to be reported as VA in the sky condition. In this photo, it may be difficult to distinguish this ash plume from what you could perceive as a convective cloud. Ash plumes tend to be darker and occur in the vicinity of volcanoes. Being familiar with your surroundings and nearby geographic features can help you correctly identify such features. The following image shows volcanic ash falling over the ocean. The sailing vessel that recorded this photo accumulated enough ash in ~30 minutes to require five hours of cleaning.
