If your mercurial barometer reads 30.50 inches (1033 millibars) and the temperature is 56°F (13°C), what is the correct reading at 55°N, 150°W?
Official USCG Answer & Rule Citation
Correct Answer: Option B — 30.45 inches (1031 millibars)
Mercurial barometer readings require corrections for temperature and gravity per Bowditch tables. Applying latitude 55N, elevation/temperature corrections to a reading of 30.50 inches at 56F reduces the pressure value to 30.45 inches (1031 millibars).
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