Narrative:

En-route between ZZZ and phx we received several ACARS messages from our dispatcher advising of an area of weather along our route. Approaching this area; radar returns indicated that a deviation north of our flight plan would keep us clear of the first area of weather and then a southwesterly turn would allow for the flight to transit the weather in a gap in the weather which had developed. We requested a deviation right of course from mci center. Deviations 'north of course' were approved and the controller said that we were 'cleared direct zun when able.' we turned to an initial heading of 270 degrees and paralleled the weather on the north side. Approaching the gap in the weather we initiated a southwesterly turn and began to transit the weather between two large cells. At this point; mci center asked if we had turned direct zun. A track direct zun would have still been too close to the weather and would be a slight right turn. We told the controller that we were not yet direct zun. He said that we were 'now deviating left of course and our clearance was to deviate right of course.' we told the controller that we were still 10 miles north (right) of our original course line. He said that the original course was not what determined right or left deviations but rather any left turn would have required a left of course clearance. He then re-cleared the flight to 'deviate left of course and proceed direct zun when able.' within a few miles (5) we were able to turn direct zun. This only required about a 3 degree turn. The flight cleared the weather and proceeded uneventful to phx. There was confusion between the flight crew and center controller on the definition of our clearance. The controller stated that a right deviation clearance constantly creates a new course line and turning back across that new line requires a new clearance to deviate left of the course. The crew understood the clearance to 'deviate right; direct zun when able' afforded the flight turns to avoid weather north (right) of course and turn towards zun. The flight turned left to avoid the radar returns but always remained 'right' of the original track by 8-10 miles. To my knowledge there was no loss of separation as there weren't any TCAS targets and the controller never issued a heading for traffic. ATC just wanted to know when we were direct zun. Altitude remained constant at FL340. I do not know if the controller considered our track as not complying with his clearance; hence; this report. Cause; confusion between the flight crew and ATC controller on the exact definition of the clearance issued. By deviating right of course and then turning left to avoid weather the controller stated the left turn required a new clearance. While the flight crew determining remaining right of original course and clearance to fly 'direct zun when able' afforded left turns across the weather so long as we did not end up left of our original track. In either case deviations were necessary to avoid the weather en-route. It was when the flight tracked across a direct zun course-line and became slightly south of that track that the confusion was discovered and when the controller queried the crew.

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Original NASA ASRS Text

Title: Air Carrier with ZKC described the confusion that ensued when a weather deviation clearance was issued. The confusion centered around direction of deviation turn and/or location relevant to the weather; i.e. north; south etc.

Narrative: En-route between ZZZ and PHX we received several ACARS messages from our Dispatcher advising of an area of weather along our route. Approaching this area; RADAR returns indicated that a deviation north of our flight plan would keep us clear of the first area of weather and then a Southwesterly turn would allow for the flight to transit the weather in a gap in the weather which had developed. We requested a deviation right of course from MCI Center. Deviations 'north of course' were approved and the Controller said that we were 'cleared direct ZUN when able.' We turned to an initial heading of 270 degrees and paralleled the weather on the North side. Approaching the gap in the weather we initiated a Southwesterly turn and began to transit the weather between two large cells. At this point; MCI Center asked if we had turned direct ZUN. A track direct ZUN would have still been too close to the weather and would be a slight right turn. We told the Controller that we were not yet direct ZUN. He said that we were 'now deviating left of course and our clearance was to deviate right of course.' We told the Controller that we were still 10 miles north (right) of our original course line. He said that the original course was not what determined right or left deviations but rather any left turn would have required a left of course clearance. He then re-cleared the flight to 'deviate left of course and proceed direct ZUN when able.' Within a few miles (5) we were able to turn direct ZUN. This only required about a 3 degree turn. The flight cleared the weather and proceeded uneventful to PHX. There was confusion between the flight crew and Center Controller on the definition of our clearance. The Controller stated that a right deviation clearance constantly creates a new course line and turning back across that new line requires a new clearance to deviate left of the course. The crew understood the clearance to 'deviate right; direct ZUN when able' afforded the flight turns to avoid weather North (right) of course and turn towards ZUN. The flight turned left to avoid the RADAR returns but always remained 'right' of the original track by 8-10 miles. To my knowledge there was no loss of separation as there weren't any TCAS targets and the controller never issued a heading for traffic. ATC just wanted to know when we were direct ZUN. Altitude remained constant at FL340. I do not know if the Controller considered our track as not complying with his clearance; hence; this report. Cause; confusion between the flight crew and ATC Controller on the exact definition of the clearance issued. By deviating right of course and then turning left to avoid weather the Controller stated the left turn required a new clearance. While the flight crew determining remaining right of original course and clearance to fly 'direct ZUN when able' afforded left turns across the weather so long as we did not end up left of our original track. In either case deviations were necessary to avoid the weather en-route. It was when the flight tracked across a direct ZUN course-line and became slightly south of that track that the confusion was discovered and when the controller queried the crew.

Data retrieved from NASA's ASRS site as of July 2013 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.