Types of Aviation Weather Information

The FAA has identified three distinct types of weather information available to pilots and operators: Observations (raw sensor/human data), Analyses (interpreted current conditions), and Forecasts (predicted future weather).

• Observation
  • Aviation Routine Weather Report (METARS)
  • Radar Summary Chart
  • Pilot Reports (PIREPs)
  • In-Flight Weather Advisories (AIRMETs & SIGMETs)
• Analyses
  • Surface Analysis Chart
• Forecasts
  • Terminal Aerodrome Forecast (TAF)
  • Meteorological Impact Statements (MIS)
  • Prognostic Charts (Prog Charts)
  • Convective Outlook
  • Wind and Temperature Aloft (FB)

We will be talking about some of the graphic reports in this section. Printed reports are further introduced in Weather Services (Printed Reports).

Surface Analysis Chart

• Shows weather conditions as of the valid time shown on the chart.
• Includes locations of high and low pressure systems and associated fronts.
• Issued every 3 hours, eight times daily (0000Z, 0300Z, 0600Z, 0900Z, 1200Z, 1500Z, 1800Z, 2100Z).
• Provides surface weather observations for a large number of reporting points (station model).

Significant Weather (SIGWX) & Prognostic (Prog) Chart

Significant weather charts are issued by World Area Forecast Centers displaying cloud, turbulence, jet stream, tropical cyclone, and volcano forecast information.

Low-Level Significant Weather Prog Charts (LLSWPC)

• Covers the conterminous United States (CONUS) and the coastal waters, depicting a “snapshot” of weather expected at the specified valid time.
• Provides information from the surface to FL240 (400 mbs: pressure level of 400 millibars).
• Issuance:
  • 4 times per day (0000, 0600, 1200, 1800).
  • WAFC SIGWX forecasts are 24-hour forecasts. That means they represent the expected weather 24 hours after the time of observation/analysis.
  • Per ICAO Doc 8896, WAFC SIGWX forecasts are ‘usable’ for a period of time extending from 3 hours before to 3 hours after the stated ‘fixed’ validity time.

• Altitudes from the surface to 17,999’ are referenced using MSL altitudes.
• Altitudes from 18,000’ to FL240 are referenced using pressure altitude.
• Provided in two forecasts in 4 panels:
  • Top: Surface to FL240 (400MB); 12/24 hour.
  • Bottom: Surface; 12/24 hour.
• Contents:
  • Flying Categories: IFR, MVFR (Marginal Visual Flight Rules), VFR NOT DEPICTED.
  • Turbulence.
  • Freezing Levels.

Mid-Level Significant Weather (SIGWX) Charts

• Provides a forecast of significant en route weather phenomena over a range of FLs from 10,000 ft MSL to FL450.
• Issuance: 4 times daily.
• Content: Non-Convective Clouds with Moderate or Severe Icing and/or Moderate or Severe Turbulence.

High-Level Significant Weather Prog Charts (HLSWPC)

• HLSWPC is a day 1 forecast of significant weather in the CONUS from FL250 to FL630.
• Provided for the en route portion of international flights.
• Issuance: 4 times daily.
• Contents:
  • Thunderstorms and Cumulonimbus Clouds (CB).
  • Moderate or Severe Turbulence.
  • Moderate or Severe Icing.
  • Jet Streams.
  • Tropopause Heights.
  • Tropical Cyclones.
  • Volcanic Eruption Sites.

Short-Range Surface Prognostic (Prog) Charts

• Combines WPC forecasts of fronts, isobars, and high/low pressure systems with the NWS’ National Digital Forecast Database (NDFD) digital forecasts.
• Short-range surface prognostic (prog) charts focus on predicting pressure systems, fronts, and precipitation at the surface, while Low-Level Significant Weather (SIGWX) charts forecast specific aviation hazards.
• Contents:
  • Precipitation.
  • Pressure.
  • Fronts.
  • Squall Lines.

Convective Outlook Chart (AC)

• A Convective Outlook (AC) delineates areas forecast to have thunderstorms.
• Contains 2 panels: Day 1 (24-hour) on the left; Day 2 (48-hour) on the right.
• Issued as required.
• Levels of Risks: - TSTM (light green) non-severe.
  • 1-MRGL (dark green).
  • 2-SLGT (yellow).
  • 3-ENH (orange).
  • 4-MDT (red).
  • 5-HIGH (magenta).