SkarpChapter 11 of 23
TAFs, Automated Observations, and Weather Charts
Forecast conditions rarely remain constant throughout a mission window. By following TAF change groups and cross-checking automated observations and charts, pilots learn to detect the exact period when a safe plan may become unacceptable.
1. Build a Forecast Timeline, Not a Snapshot
Weather is a timeline
A METAR describes observed weather at a time. A TAF forecasts expected weather over a future valid period. Your mission decision must cover the entire launch-to-recovery window, not just the weather at takeoff.
Use a layered briefing
Start with observations, convert the TAF into time blocks, then cross-check charts and graphics. The goal is to find the controlling conditions: the worst reasonably expected conditions during your operation.
Part 107 operational meaning
A station forecast is not a promise for your launch point. Local terrain, water, buildings, showers, and thunderstorms can create important differences. Leave margin when conditions are changing or inconsistent.
2. Decode the Core TAF Line
The order of a TAF
A typical U.S. TAF begins with an identifier, station, issuance time, valid period, then the initial forecast conditions:
`TAF KDSM 281120Z 2812/2912 17012KT P6SM SCT040 BKN080`
Decode it in order:
- `TAF`: Terminal Aerodrome Forecast.
- `KDSM`: Des Moines International Airport station identifier.
- `281120Z`: issued on the 28th day of the month at 1120 UTC. The `Z` means UTC, also called Zulu time.
- `2812/2912`: valid from the 28th at 1200Z until the 29th at 1200Z.
- `17012KT`: wind from 170 degrees true at 12 knots.
- `P6SM`: visibility greater than 6 statute miles. The `P` means
ASOS and AWOS: Where Surface Observations Come From
ASOS and AWOS: Where Surface Observations Come From
The METARs you have learned to decode mostly begin life at automated stations on the field.
ASOS — Automated Surface Observing System — is the primary surface-weather network, operated jointly by the National Weather Service and the FAA. A full ASOS suite measures wind, visibility, precipitation type and intensity, cloud height, temperature, dew point, and altimeter setting, updating continuously minute by minute.
AWOS — Automated Weather Observing System — is a family of similar stations, typically operated by the FAA, states, or airport authorities, installed in several configurations that report progressively more elements — from altimeter-only up to near-ASOS capability.
Two things matter for a remote pilot:
- They feed the reports you plan with. Automated observations become the routine METARs for their field.
- They broadcast locally. Each station transmits its current observation on a published frequency (listed on the sectional in the airport data block), and many are reachable by telephone — a way to hear the airport's actual current conditions from your launch site nearby.
The knowledge test expects you to recognize both acronyms as automated observation systems and to know they are a legitimate source of current surface conditions for flight planning.
Named Sources: Where a Legal Weather Briefing Comes From
Named Sources: Where a Legal Weather Briefing Comes From
Part 107 requires the remote PIC to assess weather before flight, and the exam expects you to know where aviation weather legitimately comes from — not just how to read it.
- aviationweather.gov — the NOAA Aviation Weather Center. METARs, TAFs, graphical forecasts, radar and satellite imagery, SIGMETs and AIRMETs, winds aloft — the standard first stop for self-briefing.
- Flight Service (1800wxbrief.com, or 1-800-WX-BRIEF) — briefings from Flight Service specialists, online or by phone.
- ASOS/AWOS broadcasts — the airport's own automated observation, on frequency or by phone, for conditions right now at the field.
General consumer weather apps are fine for situational awareness, but exam answers about briefing sources point at the aviation products above — they are quality-controlled, aviation-specific, and time-stamped in UTC like everything else you have decoded in this course.
Check: Automated Observations
Which system provides continuous, automated surface weather observations that feed routine METARs?
Which system provides continuous, automated surface weather observations that feed routine METARs?
- ASOS — the Automated Surface Observing System
- The Terminal Aerodrome Forecast network
- Flight Service specialists recording hourly readings by hand
- The graphical forecast for aviation
Show Answer
Answer: A) ASOS — the Automated Surface Observing System
ASOS (with its AWOS cousins) is the automated station network measuring surface conditions minute by minute; its observations become the field's METARs. A TAF is a forecast, not an observation, and briefers relay data — they do not generate the observations.
Key Terms
- TAF
- Terminal Aerodrome Forecast.