Significant Weather Chart Symbols

Decoding the Legend of WAFC SIGWX PNG Forecast Charts

Understanding the Issuer and Coverage

The legend on a WAFC SIGWX PNG forecast chart provides crucial information about the chart's provenance and coverage:

• ISSUED: Indicates the organization that issued the forecast, usually a World Area Forecast Center (WAFC).
• PNG: Specifies the region covered by the forecast, in this case, Papua New Guinea (PNG).
• ICAO: Denotes the International Civil Aviation Organization (ICAO) region within which the forecast is valid.
• AREA: Indicates the geographical coverage of the forecast.
• HEIGHT RANGE: Specifies the altitude range for which the forecast is applicable.
• VALIDITY TIME: Provides the period during which the forecast is valid.

Interpreting Weather Symbols and Features

Weather charts use curved lines to represent atmospheric features. These features are depicted using the following symbols:

• Pressure Systems: High-pressure systems (anticyclones) are indicated by an "H," while low-pressure systems (depressions) are marked with an "L."
• Fronts: Cold fronts are shown as blue lines with triangles pointing in the direction of movement. Warm fronts are depicted as red lines with semicircles facing the direction of travel.
• Wind: Wind speed and direction are indicated by arrows. The number of feathers on the arrow represents the wind speed.
• Precipitation: Rain is shown as blue dots, snow as white dots, and thunderstorms as red crosses.
• Cloud Cover: The percentage of cloud cover is indicated by a number within a circle.

Additional Information on Measured Values

In addition to weather symbols, the legend also includes a list of measured values and their corresponding symbols:

• Precipitation: Intensity and type of precipitation.
• Cloud Cover: Percentage of sky covered by clouds.
• Wind Speed: Knots or meters per second.
• Wind Direction: Degrees from true north.
• Front Line Boundaries: Cold fronts, warm fronts, occluded fronts, and stationary fronts.

Conclusion

Understanding the legend of WAFC SIGWX PNG forecast charts is essential for effectively interpreting weather information. By deciphering the symbols and measured values, pilots, meteorologists, and other users can gain valuable insights into current and forecasted weather conditions.