 As you've learned, when geostrophic winds fear with increasing height in a given layer, there's warm advection in the layer. On the other hand, when geostrophic winds back with increasing height in a given layer, there's cold advection in the layer. That's really helpful above the boundary layer where friction is negligible, but in the boundary layer where we can't ignore friction, the geostrophic wind and the observed wind are very different. So we can't connect observed winds veering in the boundary layer to warm advection all the time. Near Earth's surface, where friction is the greatest, winds cross surface isobars at an average of a 30-degree angle over land. As the effects of friction decrease with increasing height above the ground, winds cross local height lines at progressively smaller angles, producing a pattern of boundary layer winds that naturally veer with increasing height. To see what I mean, check out the Zero-Z surface analysis from February 26, 2007, and focus on Jacksonville, Florida. Now, surface winds here were southwesternly, and obviously cross local isobars. Now, let's compare to 925 millibars. Here's the Jacksonville observation. And now, 850 millibars. There's the Jacksonville observation again. And finally, 700 millibars. Now, by 700 millibars, winds are largely parallel to the local height line, and they have clearly veered from the surface, from southwesternly winds at the surface to west-southwesterly winds at 700 millibars. Another way to view this is with the corresponding sounding from Jacksonville. You can see the change in wind direction with height from southwesternly winds at the surface up to west-southwesterly winds above 850 millibars. So the big question then is, was there warm advection at the time in the layer? And if we look at the Zero-Z analysis of 850 millibar temperature advection, you can see that there really wasn't any warm advection of note around Jacksonville. And from a big picture standpoint, this actually makes sense. If you look at the Zero-Z surface analysis, Jacksonville was in the warm sector of a mid-latitude cyclone ahead of the cold front and south of the warm front, and that's a region where there is usually little or no warm advection. Remember, in the warm sector, temperature gradients are usually small, and small temperature gradients will give you weakened advection at best. But sometimes, veering of observed winds in the boundary layer does equate to warm advection. And let's go back and look at Wallops Island, Virginia, which is along the coast of Virginia here, where there was pretty strong warm advection going on at 850 millibars. Did the observed winds veer in the boundary layer? Well, the sounding shows that they clearly did, starting with south-easterly winds to the surface and then rotating clockwise to south-westerly winds up at 850 millibars. So if you look at Wallops Island's location, the warm advection makes sense. It's just north of a warm front and a region where we would expect some warm advection. So the moral of the story here is that you can't automatically connect veering winds in the boundary layer to warm advection. Sometimes the connection is there, but sometimes it's not. You have to look at the big picture to really know for sure. Finally, you might be asking yourself, what about winds backing with height in the boundary layer? Well, this observation means that some process must be overwhelming the effects of friction, and the most likely explanation is strong cold advection. But again, that's something you would want to verify by looking at the big picture.