ZNY Controller and flight crew described a loss of separation event involving oceanic traffic requesting a weather deviation; directed by ATC to deviate right but elected to turn left to avoid weather.
Synopsis
ZNY Controller and flight crew described a loss of separation event involving oceanic traffic requesting a weather deviation; directed by ATC to deviate right but elected to turn left to avoid weather.
Narrative
Air Carrier X requested deviation 20 NM east of L455 due to weather. [I] advised flight unable left deviation due to traffic; right deviation available. Air Carrier X was boxed in vertically by aircraft at FL380 and FL360. Air Carrier Y was the Air Carrier X's traffic on L456 approximately 50 NM away to the east and Air Carrier Y was unable higher for at least another 1/2 hour and I was unable to issue decent clearance due to northbound traffic for Air Carrier Y. Air Carrier X advised he was declaring a weather emergency and going 40 NM left of L455. I advised Air Carrier X of Air Carrier Y's PRHCA estimate and altitude. I advised Air Carrier Y that Air Carrier X was deviating without a clearance and advised Air Carrier Y of Air Carrier X's MACOR estimate and altitude. Air Carrier X reported Air Carrier Y 'In Sight'. As far as I know Air Carrier Y never saw Air Carrier X and according to ATOP; Air Carrier Y was behind Air Carrier X. After Air Carrier X finished deviating I asked flight for a PIREP. Flight described a bad thunderstorm; no mention of turbulence. I also asked a flight on same route at FL350 their flight conditions; they said IMC; moderate chop; aircraft did not deviate at all. This flight was only about 10 minutes in trail to Air Carrier X. Nothing could have prevented this. The last 5-6 aircraft had flown directly through this weather and there was little room to move other aircraft. Air Carrier X could have deviated all they wanted to the right; but insisted on going left; into traffic.
Second reporter narrative
I was informed that the FAA had chosen to violate a flight of which I performed as the First Officer and the pilot flying. The Captain was the pilot not flying. We were enroute to TJSJ. The Captain used Captain's emergency authority with New York AIRINC to deviate left (east) of track by approximately 18.5 miles for weather (thunderstorms) enroute on airway L455. This deviation occurred north of MCOOP Intersection at FL370. The weather was a west-to-east band in the vicinity of MCOOP with tops of the storms above approximately FL400. Continuous moderate chop was encountered approaching the area and during deviation around said storm in the clear. We did not enter the storm cell; and remained in the clear at all times. The Captain requested left deviation from New York AIRINC for weather avoidance. A right deviation would not have been safe. After a delay; New York AIRINC advised the Captain that left deviations were not approved; but a right deviation was approved. Due to weather conditions; the Captain advised New York AIRINC that he was using Captain's Emergency authority to deviate left of track. New York AIRINC advised of southbound traffic to our left (east) on a parallel track also at FL370. The Captain advised New York AIRINC that this traffic was in sight during the deviation and on TCAS. At no time did we and the adjacent southbound traffic at FL370 get close enough for any TCAS alerts. We rejoined airway L455 approximately 10 miles north of MACOR Intersection. Unfortunately; we were unable to climb above/over the weather. As mentioned above; a right deviation was not advisable/safe.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.