Date: 201210
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Weather elements / visibility: Rain
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Second aircraft: DC-10 Undifferentiated or Other Model
Reporter organization: Government
Reporter function: Supervisor / CIC
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Communication Breakdown
Anomaly: ATC Issue All Types
Detector: Person Air Traffic Control
Result: Air Traffic Control Issued New Clearance
Contributing factors: Procedure; Human Factors; Weather
Primary problem: Human Factors

Narrative: 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.




Synopsis: 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.