Meteorological charts and flight documentation (surface and upper-air charts, significant weather charts, station model)
This domain tests interpretation of surface charts, upper-air charts, significant weather charts and station models for flight planning.
Chart types
Surface charts show isobars, fronts, pressure centres and station plots. Upper-air charts at 850, 700, 500 and 300 hPa show geopotential height contours, temperature, wind and humidity; lower heights at a given pressure mean colder, denser air. The 500 hPa chart is useful for troughs, ridges and steering flow; the 300 hPa chart shows jet-stream winds. Significant weather charts depict CB, icing, turbulence, tropopause height, jet streams, fronts and tropical systems. Thickness, such as 1000–500 hPa, indicates mean temperature.
Station model
A station plot gives temperature, dew point, pressure, pressure tendency, wind barb, cloud cover, present weather and visibility. Wind barbs: half barb 5 kt, full barb 10 kt, pennant 50 kt; the shaft points into the wind. Closer isobars mean a stronger pressure gradient and stronger wind. Lows are cyclonic; highs are anticyclonic.
Worked example
A 500 hPa chart shows a deep trough west of a station and a 30 kt south-westerly wind; the surface chart shows a cold front approaching. The trough supports ascent ahead of it, so expect thickening cloud and precipitation near the front. If the 500 hPa wind is much stronger than the surface wind, vertical shear is present and thunderstorms may become organized.
Traps
Contours are not isobars. Chart times are UTC. A trough is not a front. Wind barbs show the direction the wind comes from. SIGWX charts are not aerodrome forecasts. Do not read 500 hPa height as altitude in feet.