The Open Door

I took this shot along Center St in Fernandina Beach, FL recently.  It was a very rainy day and I was hurrying to catch up to my wife when I passed this door standing partially open.  I snapped off 4 quick shots and kept going.  I started processing the photos and noticed that the white blur was a different shape in each of the photos even though I was standing perfectly still and the 4 shots occured within seconds of one another.  I didn't see the glare while I was taking the shot.  I expect that it is purely a natural reaction caused by the light coming from the top of the stairs but it is still remarkable.