A320
Air Traffic Control Fully Certified
Situational Awareness; Communication Breakdown
ATC Issue All Types
Air Traffic Control Issued New Clearance
Procedure; Human Factors; Weather
As FLM; I was quick-looking the sector from another sector due to weather; deviating and moderate-high traffic volume. Sector was split and; although it was not 'red'; I put a D-Side in. When Air Carrier X and Air Carrier Y were approximately 60 miles apart and head-on; I noticed Air Carrier X had been given climb from FL350 to FL370. With head-on traffic at FL360 and weather/precipitation in the area; I measured the distance of the head-on traffic on the scope that I was using to quick-look. The climb clearance was a good clearance and did not originally look risky; although it beared watching. Air Carrier X was climbing at a normal rate which was working well to top the traffic but; as the traffic continued; Air Carrier X started to slow the climb at FL366 and stayed at FL366 for a few 'hits'. At this point; I walked over to the sector. The aircraft reached FL367 for 1 'hit'. The head-on traffic; Air Carrier Y; was 20 NM away at that point. The altitude read out then descended and read FL366 again. I heard the Controller inquire about the climb. I told her to turn the aircraft. She issued a 'turn 20 degrees right...correction left.' There was very little time as the closure rate was high and I told her again to turn the aircraft. I told her to give him a heading. She again issued a degree turn. I told her to turn the other aircraft too. She issued a degree heading to Air Carrier Y also at that time. Air Carrier Y had to be turned left/South; which was toward the weather he was deviating around. The sector was split and there was a D-Side working with the Radar Controller; assigned by me. It was not a 'red' sector. When the R-Side Controller and I discussed the event; I recommended the use of an assigned heading rather than a degree turn. That way; the pilot has less to think about and can just enter a heading into their equipment. Also; we discussed how weather/precipitation in the vicinity can affect traffic in unexpected ways. With precipitation and deviations; do not issue a climb with head-on traffic. I also recommended the R-Side pay more attention to the tone of voice. Listening to the tapes; the Controller realized how 'NOT' urgent the control actions seemed. The Controller originally thought that they were using a stern tone of voice. We talked about how; in actuality; the tone of voice was quite pleasant; and did not convey urgency. We discussed the balance of not panicking but letting the pilots know more of the story so they respond how we need them to.
Enroute Supervisor described a developing head on event involving two Air Carriers and weather deviations; the reporter eventually directing the Controller to turn both aircraft saving separation.