FM-15, or METAR, is the WMO standard format for aviation routine weather reports. Typically reported hourly, it is the primary observation format for US stations and many international airports, providing the data for “HourlyActuals.”
Because METARs are issued every hour (and even more frequently during “SPECI” or special weather changes), they provide the high-resolution timeline needed to verify “Frontal Timing.” When a model “Busts” by 10 degrees, the METAR archive is the first place a meteorologist looks to see exactly when the temperature dropped.
The RMK section of an FM-15 report often contains highly specific data, such as “Sea Level Pressure” or “Hourly Precipitation Amount” to the hundredth of an inch. This is the “gold mine” for data scientists who search for “METAR RMK parsing” to extract the most precise “Actual” values for their models.
The ASOS stations are the hardware that actually generates the FM-15 METAR report. While the ASOS is the “sensor,” the METAR is the “language” it uses to communicate. Professionals search for “METAR transmission latency” to ensure their real-time “Data Assimilation” isn’t being slowed down by network issues at the airport.