Wind: Global, Local and Upper-Air Circulation
Global circulation
Unequal heating drives the Hadley, Ferrel and Polar cells. The trade winds blow from the subtropical highs toward the equatorial trough, deflected by the Coriolis force to become northeasterly in the northern hemisphere and southeasterly in the southern. The subtropical highs, such as the Pacific and the seasonal Asian highs, shape Brunei's weather. Upper-air flow is broadly westerly in middle latitudes, with jet streams marking the strongest winds.
Geostrophic and gradient wind
Above the friction layer, wind blows nearly parallel to the isobars, with low pressure to the left in the northern hemisphere. Near the surface, friction turns the wind about 30° across the isobars toward low pressure and reduces its speed.
Local winds
Sea breezes blow onshore by day, land breezes offshore by night. Valley winds blow upslope by day and downslope by night. Anabatic and katabatic flows follow the same pattern. Mountain waves produce strong downdrafts on the lee side. In Brunei, coastal sea-breeze effects and afternoon convection are significant for take-off and landing planning.
Traps
Do not confuse veering (clockwise) with backing (anticlockwise). Buys Ballot's law applies in the northern hemisphere with your back to the wind and low pressure on your left. Remember that surface wind is always weaker and more cross-isobar than the geostrophic wind.
Worked example
In the northern hemisphere, if you stand with your back to the wind, low pressure lies to your left. This quickly tells you which side of a low you are on.