Decoding Guide
Aviation Surface Observations
Description:
This product graphically depicts the latest surface observations from selected stations throughout the U.S.
Issuance:
Hourly
Data Sources:
Surface Observations
Depiction:
A white wind barb is
used to indicate sky coverage, wind speed, and direction. Yellow text next
to the barb gives the station identifier, temperature, dew point, pressure,
visibility, and the lowest ceiling altitude and coverage.
Example:
This example depicts a typical late fall observation from Indianapolis, Indiana
(IND). The last observation indicates a temperature of 52 degrees and a
dew point 26 degrees. Sky is broken with winds out of the South at 15kts
(wind barb
notation). The current barometric pressure is 30.12 inches of
mercury and visibility is 10 statute miles. The "150S" designation
immediately to the right of the wind barb indicates both the altitude and
coverage density of the LOWEST cloud layer. The first three digits indicate
the ceiling altitude in hundreds of feet. The 'S' that immediately follows
indicates that the clouds are scattered. Possible values of the coverage
density indicator are:
| Abbrev. | Coverage Density |
|---|---|
| CLR | Clear |
| F | Few |
| S | Scattered |
| B | Broken |
| O | Overcast |
Although the "150S" indicates a scattered clouds, the wind barb shows broken coverage. This indicates that a broken layer lies above the scattered layer at 15,000 ft.
(For FAA purposes 'scattered' or 'few' clouds do not constitute a
"ceiling", however, the altitude of any reported cloud layer is
portrayed on the map regardless.)