Aviation Routine Weather Report (METAR)
Terminal Aerodrome Forecast (TAF)
Graphical Forecasts for Aviation (GFA)
Winds and Temperatures Aloft Forecast (FB)
Inflight Weather Advisories (WA, WS, WST)
Tropopause Height/Vertical Wind Shear Prognostic Chart
Significant Weather Prognostics
An international weather reporting code is used for weather reports (METAR) and forecasts (TAFs) worldwide. The reports follow the format shown in Figure 7-1.

Figure 7-1. TAF/METAR weather card
For aviation purposes, the ceiling is the lowest broken or overcast layer, or vertical visibility into an obscuration.
Cloud tops, icing, and turbulence can only be observed directly from the flight deck. While the FAA encourages pilots to report inflight weather, a report of any unforecast weather is required by regulation. A pilot report, or PIREP (UA), is usually transmitted in a prescribed format. See Figure 7-2.

Figure 7-2. Pilot report form
Turbulence and icing should be reported by using the intensity tables shown in Figure 7-3 and Figure 7-4.

Figure 7-3. Icing intensities

Figure 7-4. Turbulence reporting criteria
A TAF is a concise statement of the expected meteorological conditions at an airport during a specified period (usually 24 hours). TAFs use the same code used in the METAR weather reports (See Figure 7-1).
TAFs are issued in the following format:
TYPE / LOCATION / ISSUANCE TIME / VALID TIME / FORECAST
Note: The “/” above are for separation purposes and do not appear in the actual TAFs.
The GFA is an interactive web-based display providing continuously updated observed and forecasted weather information over the continental United States (CONUS). It is intended to give users a complete picture of weather critical to aviation safety. The GFA display shows user-selected weather categories, each containing multiple fields of interest at altitudes from the surface up to FL480. Depending on the field of interest chosen, weather information is available from -6 in the past (observed) to +15 hours in the future (forecasted).
The GFA is not considered a weather product but an aggregate of several existing weather products. The information and data from the various weather products are overlaid on a high-resolution basemap of the United States: aviationweather.gov/gfa. The user selects flight levels and current time period for either observed or forecasted weather information. Mouse clicking or hovering over the map provides additional information in textual format, such as current METAR or TAF for a selected airport. The GFA replaces the textual Area Forecast (FA) for the CONUS and Hawaii with a more modern digital solution for obtaining weather information.
The FB is displayed in a 6-digit format (DDffTT). It shows wind direction (DD), wind velocity (ff), and the temperature (TT) that is forecast to exist at specified levels. For example, “234502” decodes as: winds from 230° true north, at 45 knots, temperatures 02°C.
When the wind speed (ff) is between 100 and 199 knots, the wind direction (DD) portion of the code will be greater than 50. In cases such as this, you will need to subtract 50 from the coded wind direction, and add 100 to the coded wind speed in order to decipher the code. For example, “734502” decodes as: winds from 230° true north at 145 knots, temperature 02°C.
Temperatures with a negative symbol in front of them (DDff-37) are negative. For flight levels above FL240, temperatures are always negative and will not have a negative symbol. Light and variable winds or wind speeds below 5 knots are indicated by 9900, followed by the forecast temperature. For example, the coded winds aloft forecast for flight level FL270 is “990017” and decodes as: winds are light and variable, temperature -17°C.
The observed winds aloft chart shows temperature, wind direction, and speed at selected stations. Arrows with pennants and barbs indicate wind direction and speed. Each pennant is 50 knots, each barb is 10 knots, and each half barb is 5 knots. Wind direction is shown by an arrow drawn to the nearest 10 degrees, with the second digit of the coded direction entered at the outer end of the arrow. Thus, a wind in the northwest quadrant with the digit 3 indicates 330°, and a wind in the southwest quadrant with the digit 3 indicates 230°.
Inflight Weather Advisories advise pilots en route of the possibility of encountering hazardous flying conditions that may not have been forecast at the time of the preflight weather briefing.
AIRMETs (WA) contain information on weather that may be hazardous to single engine, other light aircraft, and VFR pilots. The items covered are moderate icing or turbulence, sustained winds of 30 knots or more at the surface, widespread areas of IFR conditions, and extensive mountain obscurement.
SIGMETs (WS) advise of weather potentially hazardous to all aircraft. The items covered are severe icing, severe or extreme turbulence, and widespread sandstorms, dust storms or volcanic ash lowering visibility to less than 3 miles.
SIGMETs and AIRMETs are broadcast upon receipt and at 30-minute intervals (H + 15 and H + 45) during the first hour. If the advisory is still in effect after the first hour, an alert notice will be broadcast. Pilots may contact the nearest FSS to ascertain whether the advisory is pertinent to their flights.
Convective SIGMETs (WST) cover weather developments such as tornadoes, lines of thunderstorms, and embedded thunderstorms; they also imply severe or greater turbulence, severe icing, and low-level wind shear. When a SIGMET forecasts embedded thunderstorms, it indicates that the thunderstorms are obscured by massive cloud layers and cannot be seen. Convective SIGMET bulletins are issued hourly at H + 55. Unscheduled convective sigmets are broadcast upon receipt and at 15-minute intervals for the first hour (H + 15; H + 30; H + 45).
Telephone Information Briefing Service (TIBS), provided by FSS, is a system of automated telephone recordings of meteorological and aeronautical information issued throughout the United States. Based on the specific needs of each area, TIBS provides route and/or area briefings in addition to airspace procedures and special announcements concerning aviation interests that may be available. Depending on user demand, other items may be supplied; for example, surface weather observations, terminal forecasts, wind and temperatures aloft forecasts, etc. TIBS is not intended to be a substitute for preflight briefings from the FSS specialists. TIBS is recommended as a preliminary briefing, accessible by calling 1-800-WX-BRIEF and often will be valuable in helping you to make a “go or no go” decision.
A surface analysis chart depicts frontal positions, pressure patterns, temperature, dew point, wind, weather, and obstructions to vision as of the valid time of the chart. Pressure patterns are shown with isobar lines around the highs and lows. Isobars are solid lines depicting sea level pressure patterns. They are usually spaced at 4-millibar intervals; close spacing of the isobars indicates a strong pressure gradient. When the pressure gradient is weak, dashed isobars are sometimes inserted at 2-millibar intervals to more clearly define the pressure pattern.
A constant pressure analysis chart is an upper air weather map where all the information depicted is at the specified pressure-level of the chart. Each of the constant pressure analysis charts (850 MB, 700 MB, 500 MB, 300 MB, 250 MB, and 200 MB) can provide observed temperature/dew point spread, wind, height of the pressure surface, and the height changes over the previous 12-hour period.
A tropopause height/vertical wind shear prognostic chart is a two-panel chart containing a maximum wind prognostic chart and a vertical wind shear prognostic chart. The chart is prepared for the contiguous 48 states and is available once a day with a valid time of 18Z. It shows the temperature, pressure, and wind at the tropopause.
A low-level significant weather prognostic chart (surface to 24,000 feet) portrays forecast weather which may influence flight planning, including those areas or activities of most significant turbulence and icing. It is a four-panel chart; the two lower panels are 12- and 24-hour surface progs. The chart is issued four times daily. The chart uses standard weather symbols as shown in Figure 7-5.

Figure 7-5. Significant weather prognostics
The high-level significant weather prognostic chart (24,000 feet to 63,000 feet) outlines areas of forecast turbulence and cumulonimbus clouds, shows the expected height of the tropopause, and predicts jet stream location and velocity. The chart depicts clouds and turbulence as shown in Figure 7-6.

Figure 7-6. Prognostic chart depictions
The height of the tropopause is depicted in hundreds of feet MSL and is enclosed in a rectangular box. Areas of forecast moderate or greater clear air turbulence are bounded by heavy dashed lines and are labeled with the appropriate symbol and the vertical extent in hundreds of feet MSL. Cumulonimbus clouds imply moderate or greater turbulence and icing.
The lifted index is the temperature difference between an air parcel lifted adiabatically and the temperature of the environment at a given pressure height in the troposphere of the atmosphere, usually 500 mb. The lifted index chart is often used as an indicator of severe weather. When the value is positive, the atmosphere (at the respective height) is stable, and when the value is negative, the atmosphere is unstable.
[10-2024]