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What determines the direction that a wind blows? I understand that the nature of my question is immensely broad but I see no other way to phrase the question.

The question surfaced in my mind when I was checking out the windmap for the South East Asian region as I was monitoring the haze conditions there.

snapshot 1602 GMT+8, 18 Sept 2019

snapshot 1602 GMT+8, 18 Sept 2019

moved my extra thoughts to comments so I don't bog down the actual description

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  • $\begingroup$ Extra thoughts: why is it that the winds shift in direction? is the wind direction heading north due to the cooling temperatures in the northern hemisphere? i understand it has something to do with lower pressure up north minute details: why are there such strong change in directions of the winds at (for example) Penang? In general, I would just like to be able to understand WHY the winds are blowing the way they are. From the micro to macro causes. From localised to global. Seasons. $\endgroup$ – S. Ong Sep 18 at 8:09
  • $\begingroup$ earthscience.stackexchange.com/questions/980/… $\endgroup$ – gansub Sep 18 at 8:10
  • $\begingroup$ Scale will make yor question more precise, do you means why does the wind blow in predictable dirrections across the globe or why does wind shift direction hour to hour on the small local level. the latter is a duplicate and I answered the former. Both is too broad as it is basically asking us to condense all of meteorology down. $\endgroup$ – John Sep 18 at 18:58
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Sunlight (heat), planetary rotation, and the shape of the land in passes over.

Prevailing wind is mostly caused by hadley cells, or the masses of air move due to the thermal difference between the pole and the equator as well as the surface of the earth and space. Thus it is the interaction of two different thermal convection cells. this moment twists into cells due the coriolis effect and the earths rotation.

Source

these cells can be somethat disrupted on the local level by things like mountains.

enter image description here

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Most places have a prevailing wind, which is the main direction the wind comes from. In UK the prevailing wind is from the south west, which moving across the Gulf Stream gives us a mild, damp, marine climate.

Winds usually come in a rotating swirl which you can often see in satellite photos. It's a swirling air mass like a hurricane, but usually far less violent, and in a low pressure system north of the Equator the air moves counter-clockwise. Meteorologists call this a cyclone. If you can visualise one of these swirling air masses moving across UK or Malaysia, the leading edge of this rotating air mass might be blowing from south-east toward the north when it first touches land, but soon after, the trailing edge will pass over the same land, and then the wind will blow in the opposite direction. A high pressure system is called an anti-cyclone, and the wind from an anti-cyclone circulates clockwise in the northern hemisphere.

The speed with which it changes direction depends on several things, but mainly the size or diameter of the rotating air mass. There is this tendency for these rotating air masses to drift from west to east. Winds are always strongest where there is low pressure and tend to be much calmer in high pressure.

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