The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to

The difference in wind direction between the surface and 5,000 feet AGL (Above Ground Level) is primarily due to a meteorological phenomenon known as wind shear. Wind shear is a change in wind speed or direction over a short distance in the atmosphere.

Here are the steps to understand this:

1. Surface Friction: At the surface of the Earth, there are many objects (like buildings, trees, and hills) that can slow down the wind and cause it to change direction. This is known as surface friction. Surface friction decreases with height, so the wind at higher altitudes is less affected by the surface and can maintain its original direction and speed.

2. Coriolis Effect: The Coriolis effect, caused by the rotation of the Earth, also influences wind direction. This effect is negligible at the surface but becomes more significant with height. It causes the wind to turn to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

3. Pressure Gradient Force: The pressure gradient force (the force which causes wind to blow from high pressure to low pressure areas) also plays a role. It can cause the wind direction to change with height, especially if there are changes in the pressure pattern.

So, in your scenario, the wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to the factors mentioned above, with surface friction being a key factor. The wind at the surface is slowed down by friction and can't follow the pressure gradient as directly as the wind aloft, causing a shift in direction.