Chapter 3a:  Aviation Weather Sources  Introduction Surface Aviation Weather Observations Aviation Weather Reports Aviation Routine Weather Report (METAR) Example: In aviation, weather service is a combined effort of the National Weather Service (NWS), Federal  Aviation Administration (FAA), Department of Defense (DOD), other aviation groups, and individuals.  Because of the increasing need for worldwide weather services, foreign weather organizations also  provide vital input. While weather forecasts are not 100 percent accurate, meteorologists, through  careful scientific study and computer modeling, have the ability to predict weather patterns, trends,  and characteristics with increasing accuracy. Through a complex system of weather services,  government agencies, and independent weather observers, pilots and other aviation professionals  receive the benefit of this vast knowledge base in the form of up-to-date weather reports and  forecasts. These reports and forecasts enable pilots to make informed decisions regarding weather and  flight safety before and during a flight.  Surface aviation weather observations are a compilation of elements of the current weather at  individual ground stations across the United States. The network is made up of government and  privately contracted facilities that provide continuous up-to-date weather information. Automated  weather sources, such as the Automated Weather Observing Systems (AWOS), Automated Surface  Observing Systems (ASOS), as well as other automated facilities, also play a major role in the gathering  of surface observations. Surface observations provide local weather conditions and other relevant information for a specific  airport. This information includes the type of report, station identifier, date and time, modifier (as  required), wind, visibility, runway visual range (RVR), weather phenomena, sky condition,  temperature/dew point, altimeter reading, and applicable remarks. The information gathered for the  surface observation may be from a person, an automated station, or an automated station that is  updated or enhanced by a weather observer. In any form, the surface observation provides valuable  information about individual airports around the country. These reports cover a small area and will be  beneficial to the remote pilot.  Aviation weather reports are designed to give accurate depictions of current weather conditions. Each  report provides current information that is updated at different times. Some typical reports are  METARs and PIREPs. To view a weather report, go to  http://www.aviationweather.gov/.  A METAR is an observation of current surface weather reported in a standard international format.  METARs are issued on a regularly scheduled basis unless significant weather changes have occurred.  A special METAR (SPECI) can be issued at any time between routine METAR reports. METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB  18/17 A2970 RMK PRESFR Remote Pilot – Small Unmanned Aircraft Systems Study Guide  15