Dash 8 Series Undifferentiated or Other Model
Air Traffic Control Fully Certified
Other / Unknown
ATC Issue All Types; Conflict Airborne Conflict
Air Traffic Control Separated Traffic
Procedure; Airspace Structure; Human Factors; Weather
There were thunderstorms to the north of my airspace; causing me to take aircraft via non-standard procedures and feed aircraft via non-standard procedures. A Dash was on a vector eastbound to keep him south of all the weather; I had just take a hand off from the east on the Hawker at 4;000 FT. The Dash was head on at 3;000 FT with 20 miles between them. On initial contact I descended the Hawker jet to 2;000 FT. I was expecting a normal rate of descent from the Hawker; however; his descent rate was very slow and not standard at all. I missed this because I was vectoring another aircraft up to the north between some of the storms as well. Then another controller called to coordinate another aircraft from the east; as I was answering and coordinating with him I noticed the Hawker jet had gone about 8-10 miles and was only then just descending through 3;000 FT; head on with the Dash with only about 4-5 miles between them. One minute prior to this; the Dash had asked for a deviation of 10 degrees to the right which I had approved. When I became aware of the head-on; I told the Hawker jet to expedite his descent and called the traffic. I instructed the Dash to turn back to the left for traffic and issued the traffic. I then went back to the Hawker and turned him to the left and issued traffic again. He reported the Dash in sight. The closest the 2 aircraft came was 300 FT vertically and .9 miles laterally. When weather is in the area; we should not be bending airspace rules and procedures. If they aircraft can't get through; then let them go and hold somewhere for a while and/or divert until the weather passes. Working outside my airspace; making all the co-ordinations and point outs myself caused me to miss the slow descent rate which the Hawker jet was performing and nearly caused a mid-air collision.
N90 Controller described an unsafe condition during a busy period when weather required multiple avoidance vectors and altering airspace procedures a condition that is not safe according to the reporter.