Weather Charts and Flight Documentation
This domain tests interpretation of the synoptic and upper-air products used for flight planning.
Surface charts
Isobars are drawn at 4 hPa intervals with lows, highs, troughs, ridges and fronts. Tightly packed isobars mean strong wind, and Buys Ballot links the pressure pattern to wind direction. Charts are timed in UTC, usually 0000, 0600, 1200 and 1800.
Upper-air charts
Standard levels are 850, 700, 500, 300 and 200 hPa; 500 hPa is about 18,000 ft and 300 hPa about 30,000 ft. Contours are geopotential metres (500 hPa typically 5,500-5,900 m), with isotherms and wind barbs in knots. Thickness between 1000 and 500 hPa indicates mean layer temperature. Jet streams appear on 300 and 200 hPa charts as bands of maximum wind.
Significant weather
SIGWX charts show cumulonimbus, icing, turbulence, jet streams, tropopause height, tropical cyclones and volcanic ash.
Worked example
A 500 hPa chart shows a closed 5,700 m low over northern Pakistan with a -22°C isotherm. Combined with moisture, cold air aloft means instability and showers or thunderstorms. The 300 hPa chart shows a 90 kt jet on the southern side of the low, so clear air turbulence is likely near the jet core.
Traps
Reading 500 hPa as 5,500 ft rather than about 18,000 ft; forgetting that low thickness means cold air; confusing chart valid time with issue time; forgetting that wind barbs show true direction in knots and upper-air heights are in metres.