Date: 201207
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Weather elements / visibility: Thunderstorm; Windshear
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: EMB ERJ 145 ER/LR
Reporter organization: Government
Reporter function: Instructor; Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Confusion; Training / Qualification; Workload
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Separated Traffic; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure; Weather
Primary problem: Weather

Narrative: I was training a Developmental on Local Control. Two aircraft were on final with level 4 and 5 weather just northwest of the field and rapidly approaching the airport. The first aircraft (Air Carrier X) was on an ILS approach landing Runway XXR he asked for the side step to XXL; trying to avoid the weather that was fast approaching. As this was happening; the windshear alert equipment went off and warned of a fifteen knot loss one mile off departure Runway XXR. I instructed the trainee to issue the warning even though we had no departures because we were probably going to have a go around. The trainee issued the warning. Air Carrier X was about to touch down when he decided to go around and he wanted a left turn out. The trainee gave the aircraft go around instructions and instructed it to climb and maintain 4;000 FT and fly heading 180. The trainee had to be prompted to do all the necessary steps to complete the go around. As this was going on; Air Carrier Y; who was 4 [miles] in trail of the other aircraft; asked the reason for the go around. At this point I keyed up and asked Air Carrier X reason for go around. He promptly responded 'wind shear.' I relayed this information to Air Carrier Y and about 5 seconds later he said he would need to go around also. While this was happening; the trainee was struggling with inputs in the ETVS to print a strip for departure and neglected to give the first go around departure frequency change. When Air Carrier Y asked for go around he also needed a left turn out. The trainee gave him a 210 heading but this go around was on a three mile final instead of short final so the heading was basically inside of the first go around. As Air Carrier Y was going around he keyed up and said with; what I felt a little bit of panic; that he needed to 'deviate.' At this point I decided I needed to take over the frequency. The pilot asked for a deviation I took that as meaning a deviation around the inclement weather. So; I made the decision to turn him left to 180. I knew this turn would most likely put him in a position closer than three miles from Air Carrier X; but at that moment I felt it was the safest thing to do. While this was happening our first go around had still not been switched to Departure and even when I gave him the appropriate frequency he came back and asked for a different one because no one was answering. I then gave him another frequency. As this was happening; Air Carrier Y said that he needed to deviate to another airport because he was minimum fuel. I told him that he could land ZZZ1 and gave him a 60 heading so start him going there. As I was talking to the pilot about this the CIC spoke up and said that ZZZ1 had similar weather to ZZZ; so I offered the pilot ZZZ2; which was about 10 miles further northwest. When this was happening; I forgot and neglected to give Air Carrier Y clearance to ZZZ2; although I did tell him that the 60 heading would be a vector for the Visual Approach to Runway XX. He accepted and I coordinated with the appropriate RADAR controllers and handed him of to satellite to be worked. In conclusion; the separation went below three miles between Air Carrier X and Air Carrier Y on the initial part of go around once Air Carrier Y was on the 60 degree heading divergence was accomplished. I was talking to at least one of the aircraft until divergence was insured and; technically; was able to provide Visual Separation between the two aircraft because the weather southeast of the field was still VFR. Right after I got off position I went to the supervisor and said that I had probably lost separation forgetting that I could provide visual between the two aircraft. I think the CIC could have been more helpful with handling the numerous pieces of coordination that had to occur in a very brief moment. I feel I should have taken over the position sooner than I did. I am a fairly new trainer and am still learning how far I should let a trainee go before taking over.




Synopsis: Tower Controller providing OJT described a conflict event when an aircraft executing a go-around due to windshear followed immediately by a second windshear go-around. The Controller noted that the trainee issued a 'cut off vector' to the second aircraft leading to the conflict.