Anybody who has walked on Locust between 38th and 40th is familiar with the Penn “wind tunnel” between our three high rise buildings. This is new to me (I spent all of my time before Penn in suburban low-building west coast), but apparently, this is a common phenomenon with tall buildings, particularly tall buildings close to one another.
The downdraught effect is when wind hits the side of a building, and the air splays outward– up, down, and to the sides. The air that flies downward then hits the ground, and again switches direction out along the ground– producing more wind. As the air that hits the ground merges with the wind already on the level, and further, joins with other air coming from other air coming from the downdraught effect of neighboring buildings, we end up with a lot of wind trying to move between two buildings. This is very similar to using your thumb to increase the water pressure coming out of a hose.
Essentially, the Penn high rises are acting as a thumb on the hose known as Locust walk.