In semi-diurnal variations of pressure, when does the lowest pressure typically occur?

In the context of semi-diurnal variations of pressure, the lowest pressure typically occurs around 0400 hours. This is associated with the diurnal cycle influenced by factors such as temperature changes and meteorological processes.

During the night, temperatures generally decrease, leading to a reduction in thermal expansions and causing air to become denser. This density increase often contributes to rising surface pressure. As dawn approaches, solar heating begins to warm the ground, causing air parcels to expand and leading to lower pressure.

In semi-diurnal patterns, pressure tends to have two high and two low points in a 24-hour cycle. The typical timing for these fluctuations often places the lowest pressure in the early morning hours just before sunrise, supporting the notion that 0400 hours is when the lowest pressure usually occurs. This general trend is reinforced by atmospheric behavior and the impact of solar heating throughout the day, which leads to the variation in pressure recognizable during semi-diurnal cycles.

Understanding this timing is crucial for predicting weather patterns, as lower pressure is often associated with inclement weather or the approach of frontal systems.