Meteorology · Pressure — Diurnal Variation
In the tropics, the barometer shows a regular daily (diurnal) rise and fall. A departure from this normal diurnal pattern is significant because it:
- AMeans the latitude has changed
- BIndicates the instrument is broken
- CMay be the first barometric sign of a tropical disturbance✓ Correct
- DHas no weather meaning
Explanation
Tropical pressure normally peaks around 1000 and 2200 and dips near 0400 and 1600 (local). When the expected diurnal rise fails to occur or the pressure falls below normal for the time of day, it can be an early warning of a tropical cyclone, even before other signs appear.
Authority: Bowditch (Pub. No. 9), Tropical Cyclones
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