Narrative:

At approximately XA15Z; we encountered moderate turbulence due to convective activity along our route of flight. I was flying the aircraft. We were on an oceanic track at fl 330. All aircraft were encountering turbulence as noted by the radio chatter on common frequency. We were eastbound when we encountered moderate turbulence due to the convective activity; and began an immediate emergency deviation north of course to avoid heavy returns on the weather radar and perceived level 3 thunderstorm activity. The winds were approximately 70 kts out of the southwest affecting the aircraft in a northerly 'push'. A north deviation was the only option; as thunderstorm heavy returns extended to the south for approximately 100 nm. A 'hole' through the weather was observed to the north on the radar as we began an immediate deviation to avoid injury to passengers and or damage to the aircraft. We cleared the weather after approximately 5 to 10 minutes and quickly navigated back to the oceanic track. We re-acquired the oceanic track a few minutes after passing the transition longitude. This emergency deviation occurred just prior to the transition longitude as we were preparing to switch from one oceanic control to another oceanic control. Our west FMC position report was sent out automatically and reported to oceanic at our position north of course. Due to the immediate nature of the weather avoidance we were unable to obtain clearance from either oceanic control. After we had cleared the weather and were correcting back to course we were selcal'ed by oceanic requesting confirmation of our position. We notified oceanic that we had deviated north of course for weather avoidance; around a 'thunderstorm'. We further notified oceanic that we had terminated our weather deviation and that we were back on track. They copied our transmission and there was no further incident. Our entire deviation was approximately a 10-15 minute evolution in which we were extremely busy flying the aircraft and navigating to avoid level 3 thunderstorm activity and constant moderate turbulence with heavy radar returns. We were unable to communicate with either oceanic control immediately as we were busy flying/navigating the aircraft; coordinating with our flight attendants/passengers; and communicating with aircraft around us on common frequency to avoid injury to passengers and possible damage to the aircraft. The wind was also a factor as it was blowing us north of track as we were deviating. We estimate that we had to deviate about 18-20 nm north of track to avoid the convective activity before we could turn back to re-acquire the track. At no time did we consider that we were in extremes with any other aircraft and took careful and cautious actions to ensure that no other aircraft was around our position as a conflict. The other pilot crew members were on break.

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Original NASA ASRS Text

Title: A B767 Captain reported deviating from an Oceanic Track because of weather at the east/west ATC Oceanic Control transition longitude but was unable to notify either Controlling agency. An automated position report alerted ATC.

Narrative: At approximately XA15Z; we encountered moderate turbulence due to convective activity along our route of flight. I was flying the aircraft. We were on an Oceanic Track at FL 330. All aircraft were encountering turbulence as noted by the radio chatter on common frequency. We were eastbound when we encountered moderate turbulence due to the convective activity; and began an immediate emergency deviation north of course to avoid heavy returns on the weather radar and perceived level 3 thunderstorm activity. The winds were approximately 70 kts out of the southwest affecting the aircraft in a northerly 'push'. A north deviation was the only option; as thunderstorm heavy returns extended to the south for approximately 100 nm. A 'hole' through the weather was observed to the north on the radar as we began an immediate deviation to avoid injury to passengers and or damage to the aircraft. We cleared the weather after approximately 5 to 10 minutes and quickly navigated back to the Oceanic Track. We re-acquired the Oceanic Track a few minutes after passing the transition longitude. This emergency deviation occurred just prior to the transition longitude as we were preparing to switch from one Oceanic control to another Oceanic control. Our west FMC position report was sent out automatically and reported to Oceanic at our position north of course. Due to the immediate nature of the weather avoidance we were unable to obtain clearance from either Oceanic Control. After we had cleared the weather and were correcting back to course we were Selcal'ed by Oceanic requesting confirmation of our position. We notified Oceanic that we had deviated north of course for weather avoidance; around a 'thunderstorm'. We further notified Oceanic that we had terminated our weather deviation and that we were back on Track. They copied our transmission and there was no further incident. Our entire deviation was approximately a 10-15 minute evolution in which we were extremely busy flying the aircraft and navigating to avoid level 3 thunderstorm activity and constant moderate turbulence with heavy radar returns. We were unable to communicate with either Oceanic Control immediately as we were busy flying/navigating the aircraft; coordinating with our flight attendants/passengers; and communicating with aircraft around us on common frequency to avoid injury to passengers and possible damage to the aircraft. The wind was also a factor as it was blowing us north of track as we were deviating. We estimate that we had to deviate about 18-20 nm north of track to avoid the convective activity before we could turn back to re-acquire the track. At no time did we consider that we were in extremes with any other aircraft and took careful and cautious actions to ensure that no other aircraft was around our position as a conflict. The other pilot crew members were on break.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.