Why would the Air Force sent a photo-recon jet to look at a weather balloon?

I was in the 9th grade in high school at the time of this siteing.  It was apx 8:00 am on a weekend when we were called outside by a neighbor to observe this object.  The object was circular and glowed an ultra-violet blue w/a solid black center.  The object was stationary directly over us and although located in the fast moving broken cloud cover it did not move.  
We watched the object for apx 30-45 minutes.  
There was a camo colored twin engine Air Force jet which came from the southeast and flew by the object.  We could clearly see the exhaust from the jet as it came towards the object.  
When the jet was apx 200-300 ft. from the object the exhaust smoke cut off and the jet glided past on one side and the exhaust resumed when the jet was apx the same distance past it.  
The jet made a circle and the same thing happened as the jet passed on the opposite side of the object.  The jet at that time left the area heading back to the southeast.  The object was apx 3-4 times ! the size of the jet.  
The official Air Force report was that the object was a weather balloon.  There was a lot of media calls about it.  
This beggs 2 questions from me that did not make any sense. (1)  How could a weather balloon stay stationary for all of the time we were watching it in the wind?  (2)  Why would the Air Force send an observation jet to look at a weather balloon?   
I looked up the jet in the library and it was a state of the art photo-recon jet of the time.  
I will never know what it really was but it would be nice if the Air Force would release the "TRUE" photos that the jet had taken.
Witness elects to remain totally anonymous; provides little contact information.  PD