Pressure also has a twelve-hour oscillation period. In one day there are two peak pressure values, which occur at around 1000 and 2200 hours. There are two lows, one at around 1600 and another at 0400 hours. The difference between the high and low values is very small in temperate latitudes (only about 1 hPa), but is much more significant in tropical and sub-tropical latitudes (about 3 hPa).
Although the diurnal pressure change in temperate latitudes is often masked by other events, absence of the expected change in lower latitudes is often a warning of impending severe weather, such as a tropical revolving storm.