Module 13 - Meteorology
Barometer Trends and Short-Range Prediction
The barometer (barograph) is one of the most useful instruments aboard for short-range weather prediction. A steady or slowly rising barometer suggests stable or improving conditions. A falling barometer warns of approaching low pressure and deteriorating weather.
The rate of fall matters: a slow fall (1–2 mb over several hours) suggests gradual change; a rapid fall (more than 5 mb in 3 hours) warns of severe weather approaching quickly. A fall of 10+ mb in 3 hours indicates a potentially dangerous storm.
Keep a log of barometric pressure readings at regular intervals (every hour or at each watch change). Plotting a pressure trend line helps you see the big picture: is the system deepening? Has the front passed? Is pressure now rising behind the cold front?
Key points
- Rising barometer = improving or stable conditions
- Falling barometer = deteriorating weather approaching
- Slow fall (1–2 mb/3h) = gradual change
- Rapid fall (>5 mb/3h) = severe weather approaching fast
- Log pressure every hour to track trends
- Standard pressure = 1013 mb (hPa)
Tip: A barometer that has been falling and then steadies or begins to rise often indicates the cold front has passed and the worst of the weather is behind you.
Continue studying Meteorology
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