These are objective elements. They’re values measured directly by instruments (pressure, temperature, dew point, wind) and reported as numeric data. Automated and augmented observations use fixed sensor locations and time-averaging to produce consistent, repeatable measurements, which is a hallmark of objective data. Subjective elements rely on human interpretation, such as describing cloud cover or weather phenomena, rather than instrument readings. AMOS Observations describe the automated system itself, not the category of the elements, and Local Observations refer to data from a local site, not to how the data are classified.

Magnetic direction is measured relative to magnetic north, while true direction is measured relative to true north. The difference between true north and magnetic north is variation. If variation is easterly, magnetic north lies to the east of true north, so the magnetic bearing to a given direction is smaller than the true bearing by that amount, meaning you subtract the easterly variation. If variation is westerly, magnetic north lies to the west of true north, so the magnetic bearing is larger than the true bearing by that amount, meaning you add the westerly variation. So, when converting from true to magnetic, you add the westerly variation and subtract the easterly variation. For example, true direction 045° with 12° east variation gives a magnetic direction of 033°; with 12° west variation it becomes 057°.

When wind sensors on the runway are inoperative, the best substitute is wind data from the runway’s own instrumentation that was recorded for that location. This data is the most reliable because it comes from the same site, with the same exposure to local influences, and has been calibrated and logged for that specific runway. It reflects actual conditions experienced at that location, making it more trustworthy than forecasts or data from distant airports. Active-end wind data isn’t available if the equipment is down, so it can’t be used. Forecast wind data is not as dependable for immediate operations since it’s an estimate of future conditions rather than current winds. Data from other airports may not represent the local wind patterns at your runway, reducing its reliability for touch-down and takeoff decisions.

Coordinating operations at the AOL and any reciprocal support from other agencies requires a formal reference that clearly lays out roles, responsibilities, interfaces, and procedures. The proper place for that is base/host unit plans or a local weather support document. These documents are specifically used to document how external support is requested and provided, who does what, when actions occur, and how information is exchanged, ensuring everyone is aligned and prepared. Including a local weather support element helps integrate weather-related considerations into the coordination, which is essential for planning and execution. A maintenance log records equipment upkeep, not interagency coordination. A safety briefing covers immediate safety information, not the formal, long-term coordination details. An interagency treaty is a high-level, formal agreement between governments and isn’t used for day-to-day base-level coordination documentation.

Augmented observations are used to supplement automated weather data with human observations for conditions that directly affect flight operations: prevailing visibility, present weather, obscurations, and all cloud height and ceiling elements. Human observers can judge the true visibility across the field, identify and classify weather phenomena, note obscurations like smoke or haze, and determine precise cloud bases and ceilings, which automated systems may not fully capture. This ensures a complete and accurate picture for planning and safety. The other options rely on sensors for measurements such as temperature variations, wind gust patterns, or humidity and dew point, which are not the elements designated for augmentation in this reporting framework.