Chapter 3a: Aviation Weather Sources  A typical METAR report contains the following information in sequential order: 1. Type of report—there are two types of METAR reports. The first is the routine METAR report  that is transmitted on a regular time interval. The second is the aviation selected SPECI. This  is a special report that can be given at any time to update the METAR for rapidly changing  weather conditions, aircraft mishaps, or other critical information. 2. Station identifier—a four-letter code as established by the International Civil Aviation  Organization (ICAO). In the 48 contiguous states, a unique three-letter identifier is preceded  by the letter “K.” For example, Gregg County Airport in Longview, Texas, is identified by the  letters “KGGG,” K being the country designation and GGG being the airport identifier. In  other regions of the world, including Alaska and Hawaii, the first two letters of the four-letter  ICAO identifier indicate the region, country, or state. Alaska identifiers always begin with the  letters “PA” and Hawaii identifiers always begin with the letters “PH.” Station identifiers can  be found by searching various websites such as DUATS and NOAA's Aviation Weather  Aviation Digital Data Services (ADDS). 3. Date and time of report—depicted in a six-digit group (161753Z). The first two digits are the  date. The last four digits are the time of the METAR/SPECI, which is always given in  coordinated universal time (UTC). A “Z” is appended to the end of the time to denote the  time is given in Zulu time (UTC) as opposed to local time. 4. Modifier—denotes that the METAR/SPECI came from an automated source or that the report  was corrected. If the notation “AUTO” is listed in the METAR/SPECI, the report came from an  automated source. It also lists “AO1” (for no precipitation discriminator) or “AO2” (with  precipitation discriminator) in the “Remarks” section to indicate the type of precipitation  sensors employed at the automated station. When the modifier “COR” is used, it identifies a  corrected report sent out to replace an earlier report that contained an error (for example:  METAR KGGG 161753Z COR). 5. Wind—reported with five digits (14021KT) unless the speed is greater than 99 knots, in which  case the wind is reported with six digits. The first three digits indicate the direction the true  wind is blowing from in tens of degrees. If the wind is variable, it is reported as “VRB.” The  last two digits indicate the speed of the wind in knots unless the wind is greater than 99  knots, in which case it is indicated by three digits. If the winds are gusting, the letter “G”  follows the wind speed (G26KT). After the letter “G,” the peak gust recorded is provided. If  the wind direction varies more than 60° and the wind speed is greater than six knots, a  separate group of numbers, separated by a “V,” will indicate the extremes of the wind  directions. 6. Visibility—the prevailing visibility (¾ SM) is reported in statute miles as denoted by the letters  “SM.” It is reported in both miles and fractions of miles. At times, runway visual range (RVR)  is reported following the prevailing visibility. RVR is the distance a pilot can see down the  runway in a moving aircraft. When RVR is reported, it is shown with an R, then the runway  number followed by a slant, then the visual range in feet. For example, when the RVR is  reported as R17L/1400FT, it translates to a visual range of 1,400 feet on runway 17 left. 7. Weather—can be broken down into two different categories: qualifiers and weather  phenomenon (+TSRA BR). First, the qualifiers of intensity, proximity, and the descriptor of the  weather are given. The intensity may be light (–), moderate ( ), or heavy (+). Proximity only  depicts weather phenomena that are in the airport vicinity. The notation “VC” indicates a  specific weather phenomenon is in the vicinity of five to ten miles from the airport.  Descriptors are used to describe certain types of precipitation and obscurations. Weather  16  Remote Pilot – Small Unmanned Aircraft Systems Study Guide 