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On shorter timescales than the seasonal changes described in Section 2.4, wind speed variations are somewhat more random and less predictable. Nevertheless, these variations contain definite patterns. The frequency content of these variations typically peaks at around four days or so. These are the ‘synoptic’ variations, which are associated with large‐scale weather patterns, such as areas of high and low pressure and associated weather fronts as they move across the earth's surface. Coriolis forces induce a circular motion of the air as it tries to move from high‐ to low‐pressure regions. These coherent large‐scale atmospheric circulation patterns may typically take a few days to pass over a given point, although they may occasionally ‘stick’ in one place for longer before finally moving on or dissipating.

Following the frequency spectrum to still higher frequencies, many locations will show a distinct diurnal peak, at a frequency of 24 hours. This is usually driven by local thermal effects. Intense heating in the daytime may cause large convection cells in the atmosphere, which die down at night. This process is described in more detail in Section 2.6 because it also contributes significantly to turbulence, on timescales representative of the size of the convection cells. Land and sea breezes, caused by differential heating and cooling between land and sea, also contribute significantly to the diurnal peak. The daily direction reversal of these winds would be seen as a 12‐hour peak in the spectrum of wind speed magnitude.