Base Velocity Image
This base velocity image is from the NWS Doppler radar in Lake Charles, LA during Hurricane Rita, September 2005. In velocity images, red colors indicated wind moving away from the radar with green colors indicating motion toward the radar. The transition zone between incoming and outgoing winds are indicated the gray-ish colors between the two. Purple indicated "range folded" areas (areas where the radar is unable to determine the radial velocity).
The actual direction of the wind is determined by drawing a line perpendicular to the gray-ish areas from the green region to red region. Mouseover the image to view wind's direction indicated by the small yellow arrows.
The radar's location is indicated by a black dot. The two arrows on either side of the black dot show the wind's direction at that point.
However as distance from the radar increases, the direction of the wind changes (indicated by the arrows at #2) and appear to be more inline with the overall circulation one would expect around a hurricane (large yellow arrow).
Why the difference? At #1, the wind is low to the ground which reduces the speed due to friction with the earth's surface. As a result, the direction is angled toward the eye of the storm.
Farther up in the atmosphere, above this frictional layer, the wind direction is more what one would expect. Yet at #3, the wind direction begins to diverge. This divergence is clockwise outflow at the top of the storm.
We see these different wind directions through the height of the storm due to the radar beam increasing in elevation as the distance from the radar increases.